|Ahead of print
Grossing and reporting of a soft tissue tumor specimen in surgical pathology: Rationale, current evidence, and recommendations
Bharat Rekhi1, Jayasree Kattoor2, Anne Jennifer3, Nandini Govindarajan4, Shantveer Uppin5, Nirmala A Jambhekar6, Annie Jojo7, Uttara Chatterjee8, Devmalya Banerjee9, Pradyumn Singh10
1 Department of Surgical Pathology, Bone and Soft Tissues, Disease Management Group, Tata Memorial Hospital, Homi Bhabha National Institute University, Mumbai, Maharashtra, India
2 Department of Pathology, Regional Cancer Centre, Thiruvananthapuram, Kerala, India
3 Department of Pathology, Christian Medical College, Vellore, Tamil Nadu, India
4 Department of Pathology, Dr Kamkashi Memorial Hospitals, Chennai, Tamil Nadu, India
5 Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India
6 Formerly, Department of Surgical Pathology, Tata Memorial Hospital, Mumbai, Maharashtra, India
7 Department of Pathology, Institute of Post-Graduate Medical Education and Research and Seth Sukhlal Karnani Memorial Hospital, Kolkata, West Bengal, India
8 Department of Pathology, Amrita Institute of Medical Sciences, Kochi, Kerala, India
9 Department of Pathology, Narayana Super Speciality Hospital, Howrah, Kolkata, West Bengal, India
10 Department of Pathology, Ram Manohar Lohia Hospital, Lucknow, Uttar Pradesh, India
|Date of Submission||05-Jul-2020|
|Date of Decision||15-Jul-2020|
|Date of Acceptance||20-Sep-2020|
|Date of Web Publication||24-Nov-2020|
Department of Surgical Pathology, Bone and Soft Tissues, Disease Management Group, Tata Memorial Hospital, Homi Bhabha National Institute University, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
Soft tissue tumors, including sarcomas are complex and diagnostically challenging tumors. This is as a result of their heterogeneity and overlapping clinicopathological, immunohistochemical and also molecular features, the latter to some extent. More than 80 types of sarcoma have been described. Current management, which is best offered at centers with active multidisciplinary care, is based on balancing oncologic and functional outcomes in such cases. This has transcended into the types of specimens received for grossing these rather uncommon tumors. Over the years, diagnostic specimens have reduced in their sizes from, open biopsies to core needle biopsies. These specimens need to be adequately and judiciously triaged for ancillary techniques, such as molecular testing. Conservative surgeries have led to resected specimens for marginal assessment. Lately, post neoadjuvant (chemotherapy or radiation therapy)-treated resection specimens of soft tissue sarcomas are being submitted for surgical pathology reporting. This article focuses on the grossing of soft tissue tumors, including sarcomas, in terms of types of specimens, grossing techniques including rationale, tissue triage, reporting, and recommendations from the surgical pathologists actively engaged in reporting musculoskeletal tumors,
based on current evidence.
Keywords: Core needle biopsy, excision specimens, grossing soft tissue tumor, margins, soft tissue sarcoma, soft tissue tumor specimen
|How to cite this URL:|
Rekhi B, Kattoor J, Jennifer A, Govindarajan N, Uppin S, Jambhekar NA, Jojo A, Chatterjee U, Banerjee D, Singh P. Grossing and reporting of a soft tissue tumor specimen in surgical pathology: Rationale, current evidence, and recommendations. Indian J Cancer [Epub ahead of print] [cited 2021 Jan 24]. Available from: https://www.indianjcancer.com/preprintarticle.asp?id=301408
| » Introduction|| |
Soft tissue sarcomas are uncommon and heterogeneous tumors, leading to a diagnostic challenge, especially for a pathologist at a community hospital. A close interaction in the multidisciplinary tumor (MDT) board enhances better understanding related to the diagnosis and treatment of these complex tumors. This practice has brought a significant effect on their management and led to an increase in disease-free and overall survival of patients harboring these rare tumors, which are associated with significant discrepancies when managed at non-specialized versus specialized centers.,,
It is important to note that a soft tissue sarcoma invariably grows centrifugally, pushing the surrounding tissue aside as they grow, leading to the development of a pseudocapsule, which often contains tumor microsatellites [Figure 1]. The myth is that shelling out of the tumor is curative, whereas the reality is that tumor seedlings might remain in the adjacent tissue of the “shelled-out” tumor.
|Figure 1: Cut surface of an excised soft tissue tumor showing a grey-white, fairly well-circumscribed tumor with its pseudocapsule (arrowheads) blending with adjacent soft tissues (asterisk). The resection surface is painted|
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The three key questions (What is it? Has it been cleared completely? How will it behave?) that need to be answered while formulating a pathology report of a soft tissue mass are first, the nature of the lesion (tumor, tumor-like lesion, pseudosarcoma, or a sarcoma); second, in the case of an excised sarcoma, whether it has been removed completely; and finally, in case of a sarcoma, its behavior and clinical outcome. While the first clinical query is answered by exact subtyping of the tumor based on histopathological assessment, the second query can be resolved with the histopathological assessment of surgical/resection margins. Finally, the clinical behavior of a sarcoma is based on its histopathological grading and staging.
Considering that limb salvage is now practiced, the preferred choice of treatment is surgical excision with clear margins, with an aim of balancing oncologic and functional outcomes in these patients.
It is recommended that a biopsy is performed by a musculoskeletal oncosurgeon, and reporting by a soft tissue tumor specialist. A soft tissue tumor or a sarcoma pathologist is the one who regularly reports these tumors, as a significant component of his or her daily “sign-outs.” A sarcoma pathologist should regularly participate in the soft tissue part of the bone and soft tissue pathology external quality assurance scheme (EQAS) and be part of a properly constituted sarcoma multidisciplinary team.
Types of soft tissue tumor specimens:
- Core needle biopsy, including computed tomography (CT)-guided: This is preferred for a primary diagnosis. Fine-needle aspiration cytology (FNAC) is mostly preferred for recurrent and metastatic lesions. FNAC for a primary diagnosis of a soft tissue mass may be attempted, only at specialized centers, dealing with high volume of such cases and with access to ancillary techniques, including on cytology material, such as cell blocks etc. Frozen sections are not preferred for a primary diagnosis of a soft tissue tumor. In case of a surgical excision, the closest resection margin should be processed, during intra-operative (frozen section) consultation.
- Incisional biopsy: Open biopsy, especially when the core needle biopsy has failed and yielded insufficient or unsuitable diagnostic material. Routinely, an open biopsy, although most representative, is not preferred, for fear of contamination of tissue planes. This can further lead to a wider excisions, and a relatively higher associated morbidity.
- Excisional biopsy: It is generally for superficial lesions upto 2 cm. An excisional biopsy for lesions exceeding 2 cm could possibly lead to contamination of the adjacent tissue planes, thereby making re-excision more extensive.
- Excision specimens with resected margins.
- Re-excision of the revised margin.
- Radical excision including en bloc resection of a compartment or an amputation specimen.
- Post-treatment (chemotherapy and/or radiation therapy) excision specimens.,,
Fixation: It is crucial to note that all the tissues selected for processing in histopathology should be fixed in an adequate amount of 10% neutral buffered formalin (NBF) overnight, limiting the cold ischemia time as much as possible. This is especially true for small/core biopsies.
Even though fresh tissue is considered to be ideal for molecular techniques, referral centers have to handle requests for molecular testing. In those scenarios, paraffin blocks are available for ancillary testing, including immunohistochemistry and molecular and/or molecular cytogenetic techniques, including reverse transcriptase-polymerase chain reaction (RT-PCR), Sanger sequencing, fluorescence in-situ hybridization (FISH), and lately, next-generation sequencing (NGS). 10% NBF is an ideal fixative. Other fixatives, especially acid-based, are useless for tissues intended to be subjected to molecular testing. The volume of fixative to the large specimen should be 3:1, in order to achieve an optimal fixation.
It would be ideal to store fresh or frozen tissue (representative of the tumor) in a repository for future molecular studies, such as genome sequencing and “in-vitro” drug testing, but this is related to the capacity of a particular laboratory and institute. Approximately 1 cm3 of tissue cut into small 0.2 cm fragments may be snap-frozen using liquid nitrogen and stored at −70°C.
Imprint smears of fresh tissue can be further utilized for ancillary techniques, such as FISH.,
It is reasonably useful to study available clinical and radiological information before initiating the grossing of soft tissue or a bone specimen. The details can be checked from the electronic records or as attached notes with the requisition form. These are helpful to identify the exact location of the tumor, with respect to its adjacent tissues and to have an idea of the purpose of surgical procedure, including the type of excision.
Grossing and rationale
Grossing of a core biopsy
Considering these tumors are heterogeneous and complex, all the tissue bits in the small biopsy specimen should be ideally counted and measured, and correlated with the radiologist's notes (if available) and processed. In case of bony bits, included in tumors involving adjacent bones, these should be separated, decalcified, and accordingly processed.
Grossing of excision specimens
- The excised specimen should be carefully oriented with its sutures (generally short suture for superior margin and long suture for lateral margin), followed by an examination of the external surface with regard to the adjacent normal structures, such as nerves, vessels, and the overlying skin. This is helpful in the identification and labeling of the resection margins, [Figure 2]. The scar of the previous biopsy should also be noted.
- The entire specimen should be measured in three dimensions.
|Figure 2: Gross appearance of an excised soft tissue tumor mass (oriented with a suture) showing a nodular, glistening external surface, and painted (with India ink) resection surface|
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The specimen should be palpated for a tumor. Radiological findings, such as magnetic resonance imaging (MRI), if available, can be useful in this regard. CT scan is useful for evaluating metastatic lesions and ultrasonography is particularly useful for cystic lesions.
- The resection margins, including the closest margin, should be noted. This is helpful in planning further management; whether a revision needs to be performed or adjuvant therapies, especially radiation therapy would be required, for an improved locoregional clearance.
- Surgical margins should be inked before cutting. In case the specimen is received in the frozen (intraoperative consultation) section room for the closest margin, it should be clearly identified, marked, and reported, and at the time of final grossing, that particular margin should not be re-grossed while other margins should be accordingly taken and processed. It is optional to use a single ink color (India ink) or different colored inks, for different margins, for clear labeling. We suggest that the ink is fixed with a mordant, such as acetone or acetic acid, and allowed to dry before cutting the specimen so that it is well reinforced and clearly identified during microscopic assessment.
- The resected specimens with their respective margins may be photographed, especially with current resources of digital pathology. These can also be photographed during frozen section assessment, for the closest margin and would be useful during reporting and also during multidisciplinary discussions, especially for the closest margins, for which further planning and management is undertaken.
- Once the specimen orientation is done, it should be serially sectioned/“bread-loafed” perpendicular to the long axis of the specimen, preferably at 1 cm interval, in order to clearly identify the tumor and its location with respect to adjacent tissues and most importantly surgical margins.
- Various areas should be identified and tumor (T) size should be measured in three dimensions. The T-size (largest dimension) in cases of sarcomas constitutes an important parameter in staging. Therefore, its documentation is crucial. It is helpful to correlate T-size with available imaging results. Small size refers to < 5 cm; intermediate is 5 cm and large size refers to a tumor size exceeding 5 cm in the largest dimension.
- It is prudent to understand and label the various margins that need to be sampled.
- During serial sectioning, the tumor should be clearly identified, including with its respective tissue compartment, especially in specimens of radical excisions, in cases of extremity-based sarcomas. It should be noted whether the tumor confines are beyond its compartment (contamination) and/or there are satellite lesions, in the compartment, other than in which the tumor is located. These are some of the reasons for which a radical excision, such as an amputation, is undertaken.
- It is important to note whether the tumor is superficial or deep-seated. All mediastinal, retroperitoneal, intraabdominal, and chest wall tumors are considered as “deep.” Deep-seated tumors have more chances of being malignant. Among benign tumors, 99% are superficial, and 95% are less than 5 cm in diameter. Very few sarcomas are superficial, for example, epithelioid sarcoma. Most sarcomas are deep-seated.
- It is noteworthy that margins of resection in retroperitoneal/abdominal tumors cannot be assessed as in extremity or other skeletal sarcomas, as these might be formed by parenchymal margins of the excised organs.
- Tumor appearance, especially of the cut surface, should be adequately described in terms of its color, appearance, and consistency, for example, whether it is yellowish (fatty), myxoid, firm, etc., [Figure 3]. Another example is the gross appearance of a specimen of pigmented villonodular synovitis that includes reddish-brown nodules, as a result of hemosiderin deposition. Areas of hemorrhage and necrosis should be recorded.
- Any 'skip lesion' in case of radical excision, including an amputation specimen, should be recorded. In case this is detected preoperatively, on imaging, it could be one of the reasons for undertaking a radical excision. Post-operatively, it could lead to offering adjuvant therapies.
- Sections to be submitted for processing include the scar tract (if present); from the various margins (preferably radial), including the closest one along with nerve and vessel cut margins.
- Sections from the different areas of the tumor (1 block/cm of the tumor, except very large tumors, which can be judiciously sampled, considering soft tissue tumors are heterogeneous.
|Figure 3: Gross appearance of the excised soft tissue tumor (wide-excision) mass (oriented with a suture). Cut surface showing a fungating tumor with a nodular, grey-white, glistening/gelatinous/myxoid appearance (microscopically, a high-grade myxofibrosarcoma), at a distance of 3.3 cm from the resection surface (margin). Dotted line constitutes a radial margin. Thickened line represents a shave margin|
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Yellowish tumor areas (perinephric fat) in a large, retroperitoneal sarcoma, which microscopically appears as a high-grade pleomorphic sarcoma, could be a well-differentiated liposarcomatous (WDLPS) component, which could lead to a correct diagnosis of a dedifferentiated liposarcoma (DDLPS), over a pleomorphic sarcoma. Conversely, grey-white areas in an otherwise largely fatty tumor could be representative of a high-grade sarcoma, leading to a diagnosis of a DDLPS, over an erroneous diagnosis of a WDLPS, or even a lipoma, [Figure 4]. The value of differentiating a DDLPS from a WDLPS is that the former requires a complete surgical excision with optional radiation therapy, especially if surgical margins are compromised for better locoregional clearance. A WDLPS in extremity location does not require adjuvant treatment in most cases.
|Figure 4: Cut surface of a large retroperitoneal dedifferentiated liposarcoma displacing the kidney with grey-white to yellow areas, reminiscent of dedifferentiated and well-differentiated components|
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- Sections with regard to adjacent normal soft tissues - For example, tumor sections from an adjacent nerve could show the origins of a nerve sheath tumor, which may be S100 protein negative.
In case the attached bone is also removed with the tumor, a section from the bone, after cutting it longitudinally with a saw, should be submitted to note tumor infiltration.
- Necrotic areas, especially for evaluating the percentage of necrosis in sarcomas (important parameter of histopathological grading of a sarcoma), adjacent to the tumor foci.
- Any skip lesion, in case of amputation specimens, should be processed, for the reasons aforementioned.
- Any lymph nodes, if submitted with the specimen. Certain sarcomas such as epithelioid sarcomas, angiosarcomas, and rhabdomyosarcomas have a propensity for lymph node metastasis.,,,
Revised margin specimens
These are received in some cases of prior resections showing positive margins. Invariably, this is in form of an elliptical specimen with a skin ellipse and a linear scar. In case there is a positive margin reported in the frozen section, a linear fibro fatty tissue with an abluminal side inked by the surgeon could be additionally submitted.
In these specimens, the circumferential and deep margins are inked. Subsequently, the specimen is transected perpendicular to long axis at 1 cm intervals In case a tumor is identified, it is processed along with its respective margins. In case no residual tumor is identified, multiple sections from the tumor bed may be submitted for processing.
Types of tumor excisions
R2: Intralesional: Surgical plane runs through the tumor. This is mostly preferred in benign tumors and considered in localized sarcomas, when wide excision is not possible, in view of involvement of major structures, such as nerves and vessels, in trunk and extremities. Another scenario is retroperitoneal and mediastinal sarcomas, when adjacent organs and major blood vessels are involved.
R1: Marginal: Surgical plane runs through the pseudocapsule, sparing adjacent vital structures and is considered especially when tumors are adjacent to vital neurovascular structures. It is noteworthy that marginal excision following preoperative radiation therapy can result in equivalent local control and amputation free survival, compared with wide/radical margins. In cases, where wide excision is not possible because of proximity to crucial structures, such as blood vessels and nerve, a planned marginal excision with postoperative radiation therapy may be appropriate for achieving disease control.,
R0: Wide: Surgical plane in the normal tissue, beyond the reactive zone, but in the same compartment. This is mostly preferred.
Radical (amputation): Surgical plane extending into the other compartments, especially considered in recurrences.,
Post chemotherapy resection specimens:
There are no standardized and established schemes for response assessment of post-chemotherapy (neo-adjuvant) treated resection specimens of soft tissue sarcomas, unlike for bone sarcomas, such as for osteosarcoma, by Huvos et al. and for Ewing sarcoma, by Picci et al. Lately, the European Organization for Research and Treatment of Cancer Soft Tissue and Bone Sarcoma Group (EORTC-STBSG) has proposed recommendations for pathological examination and reporting of post-NACT treated specimens of soft tissue sarcomas. The grossing of such specimens is mostly similar to wide excisions. The sampling should represent the intratumoral heterogeneity apart from the central slab that is entirely processed. It is recommended that the number of blocks should not go below a minimum of one block per centimeter of the largest diameter. These guidelines have also been tested in post-radiation therapy treated cases of soft tissue sarcomas and would be useful for surgical laboratories of institutions catering to such specimens.
While pediatric sarcomas, such as Ewing sarcoma and rhabdomyosarcoma, are classical examples of chemosensitive sarcomas, wherein definitive chemotherapy is offered, there are limited subtypes of adult soft tissue sarcomas that are chemosensitive, such as, synovial sarcoma, myxoid liposarcoma, and leiomyosarcoma, wherein chemotherapy is offered in adjuvant settings after MDT discussion. On the contrary, sarcomas such as, DDLPS, clear cell sarcoma of soft parts, and extraskeletal myxoid chondrosarcoma are refractory to conventional chemotherapies, which include drugs, such as doxorubicin/adriamycin and ifosfamide. Malignant peripheral nerve sheath tumor, epithelioid sarcoma, and pleomorphic sarcoma are some examples of moderately chemosensitive tumors. More recently, newer “targeted” chemotherapy options such as mTOR inhibitors (sirolimus) for perivascular epithelioid tumors (PEComas); EZH2 inhibitors for epithelioid sarcoma, and tyrosine kinase, as well as immune checkpoint inhibitors for alveolar soft part sarcoma and immunotherapy for undifferentiated pleomorphic sarcoma are being explored and offered.,, These are some examples emphasizing the value of exact histopathological subtyping of sarcomas.
Neoadjuvant chemotherapy is considered in cases of large-sized tumors (exceeding 5 cm) with high-grade, which are borderline resectable and especially chemosensitive tumors, such as synovial sarcoma, leiomyosarcoma, and myxoid liposarcoma. The intention is to down-size the tumor for an improved resection. All these decisions are made in an MDT clinic. The rationale for evaluating percentage necrosis in post-chemotherapy resection specimens is to identify whether a tumor is responsive to chemotherapy or not and for further management options that are discussed in the MDT clinic on an individual case-based approach.
Definition of an acceptable margin
An acceptable margin of normal tissue is not universally agreed upon, but is commonly accepted as 1 cm soft tissue or equivalent (e.g., a layer of fascia). There has been no consensus on the margin distance, which ranges from “negative for tumor at the inked margin,” up to 5 cm, in a review article by Kandel et al., In a much earlier study, Kawaguchi et al. proposed that in all cases of musculoskeletal tumors, the surgical margin is considered to be curative if the margin is outside a barrier and there is normal tissue between the barrier and the reactive tumor zone. In a more recent study by Gundle et al., it has been shown that resection '+1mm' classification reduced differences in local recurrence between R0 and R1, suggesting that a negative but less than 1 mm margin might be adequate with multidisciplinary treatment. The quality of the margin is more significant in recurrent tumors. Therefore, in all cases, including tumors close to the resection surface (close margins), the exact measurements of the tumor distance till the inked resection surface, including in millimeters, should be clearly recorded.
Margins of an excised soft tissue mass include shave and radial margins.
In case a tumor is close to the resection surface, a radial margin is processed and in case the tumor is away from the resection surface, a shave margin is processed. Nerve and vessel cut margins should be processed beforehand if identified with the specimen. Radial margins are more often processed in soft tissue tumor resections.
Impact of a surgical resection margin: It guides the treating surgeon whether he/she needs to revise the margin at the time of operation (intraoperative/during frozen section), or afterwards.
This helps in the further decision for need of adjuvant treatment, such as radiation therapy (RT), especially in cases of marginal and intraregional excisions, in order to reduce the chances of future recurrences, for improved locoregional clearance.
It is known that residual tumor in an incomplete (intralesional) or a marginal excision is a forerunner for future recurrences and possible metastasis that portend a grim prognosis.,
Surgical pathology reporting of soft tissue tumors, including sarcomas, is preferably based upon the recent (5th edition) World Health Organization (WHO) classification of tumors of soft tissue and bone. Soft tissue tumors are classified based on their cell of origin and further sub-classified into benign, intermediate malignant, and malignant/sarcoma subtype. More than 100 soft tissue tumors and more than 80 histopathologic subtypes of sarcomas have been described., Several specific genetic aberrations including chromosomal translocations, gene amplification, and mutations have been identified in various sarcomas, which constitute their specific genetic signatures. Molecular techniques such as fluorescence in-situ hybridization (FISH), reverse transcriptase polymerase chain reaction (RT-PCR), and next generation sequencing (NGS) can be utilized for detection of underlying genetic signatures of various sarcomas, in order to substantiate a diagnosis, for example in cases of Ewing sarcoma, synovial sarcoma, alveolar rhabdomyosarcoma, all being chemosensitive tumors but treated with different combinations of chemotherapeutic agents. It has been noted that despite reporting by an expert sarcoma specialist, the diagnosis was modified after molecular testing in 13.8% cases of selective tumor cohorts, including in 12% cases of Ewing sarcoma, 16% cases of synovial sarcoma, and in 23% cases of DDLPSs. The authors of the same study concluded that molecular testing is mandatory, despite reporting by an expert sarcoma pathologist. In view of cost and logistic constraints in countries with limited resources, cases can be triaged for molecular testing, when immunohistochemical results are equivocal, e.g., between a poorly differentiated synovial sarcoma and Ewing sarcoma and between a synovial sarcoma and malignant peripheral nerve sheath tumor. Moreover, in cases of translocation-specific sarcomas, such as Ewing sarcoma occurring at unusual sites, such as the female genital tract, kidney, to name but a few. There are several other diagnostic scenarios, which require molecular testing.
One of the success stories in soft tissue tumors has been the diagnosis of gastrointestinal stromal tumors (GISTs), which are candidates for targeted therapy, imatinib mesylate (Gleevac). This tumor most frequently occurs in the stomach, followed by small bowel, colorectum, and rarely in the esophagus. Histomorphologically, GISTs display a wide spectrum, including spindle to epithelioid cells. CKIT/CD117 and/or discovered on GIST-1(DOG1) constitute the two most crucial immunohistochemical markers for the diagnosis of GISTs. While 75% of cases of GIST harbor activating mutations of CKIT, 10% of cases harbor platelet-derived growth factor receptor alpha (PDGFRA) activating mutations, which are mutually exclusive., Nearly 5-10% cases with Wild-type CKIT and PDGFRA expression, display alterations in a subunit of succinate dehydrogenase (SDH) genes. These tumors show a lack of immunohistochemical expression of SDH and are histomorphologically characterized by epithelioid morphology and multinodularity. Tumor site, size, and mitotic count are important prognostic parameters for risk stratification in GISTs. These are further assigned tumor, nodes, metastases (TNM) stage, as per site (gastric and small intestinal). The goal of treating a GIST of size ≥2 cm is to achieve complete resection without capsular rupture. Adjuvant therapy with imatinib is offered in cases with an intermediate or high-risk of relapse., Besides certain histopathological parameters, mutational profiling has a bearing on prognosis and response to therapy (predictive). CKIT mutant tumors are relatively more aggressive than PDGFRA mutant tumors. The most common are KIT exon11 mutations. It has been further reported that gastric GISTs with exon 11 mutations are more aggressive than those with substitutions. Moreover, cases harboring KIT exon 11 mutations respond more favorably to imatinib therapy. Cases of NF1 and PDGFRA D842V GIST are not considered for adjuvant treatment with imatinib, in view of a less favorable response.
More recently, certain sarcomas have been defined by their genetic fusions, such as CIC-DUX4,BCOR-CCNB3, NTRK- positive tumors, etc., including in the recent WHO classification of tumors of soft tissue and bone.,,,
A pragmatic way of evaluating a soft tissue mass in pathology is by utilizing an algorithmic approach, including histopathological pattern recognition and pattern analysis, integrated with ancillary tests (immunohistochemical staining and molecular results) [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]. Sarcomas are graded, as per the Fédération Nationale des Centres de Lutte Contre Le Cancer (FNCLCC) grading system and staged (disease-extent), according to the TNM classification. Grading is based upon the addition of individual scores of three parameters, namely tumor necrosis, mitotic activity, and degree of tumor differentiation. Areas of tumor necrosis are sampled at the time of grossing and quantified as <50% (score 1) or ≥50% (score 2) during the microscopic assessment. The TNM clinical classification stratifies soft tissue sarcomas occurring in extremity, trunk, and retroperitoneum as Tx (primary tumor cannot be assessed), T0 (no evidence of primary tumor), T1 (tumor less than 5 cm), T2 (tumor more than 5 cm, but not more than 10 cm in greatest dimension), T3 (tumor more than 10 cm, but no more than 15 cm in the greatest dimension), and T4 (tumor more than 15 cm in the greatest dimension). However, for sarcomas occurring in the head and neck region, T1 indicates a tumor 2 cm or less in the greatest dimension; T2 is a tumor more than 2 cm, but no more than 4 cm; T3 is a tumor more than 4 cm; T4a is tumor invading orbit, skull base or dura, central compartment viscera facial skeleton, and/or pterygoid muscles a T4b includes tumor invading brain parenchyma, encasing carotid artery, invading prevertebral muscle or central nervous system by perineurial spread. Tumor grading and staging constitute standard prognostic parameters in cases of soft tissue sarcomas., It is noteworthy that tumor grade and stage cannot substitute for the histopathologic type, considering that differentiation score (related to tumor subtype) is one of the parameters for FNCLCC grading. Therefore, all three parameters along with additional data such as lymphovascular invasion; results of ancillary tests (molecular techniques), and additional biomarkers (in case tested), should be preferably incorporated in the final report of soft tissue sarcomas. Various components of the report can be included in a reporting format, based on data sets for histopathological reporting soft tissue tumors of the Royal College of Pathologists and of the College of American Pathologists (CAP) guidelines.,,,
|Figure 5: Algorithmic approach for pathological evaluation of a soft tissue mass lesion|
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|Figure 6: Landscape of diagnosis of synovial sarcoma. a. Spindle-cell sarcoma including cells arranged in a Herring-bone pattern, reported (misdiagnosed) at a referring laboratory, as a fibrosarcoma. Hematoxylin and eosin (H and E), ×200. b. Tumor cells showing epithelial membrane antigen (EMA) positivity. Diaminobenzidine (DAB), ×400. c. Focal cytokeratin 7 (CK 7) positivity. DAB, ×400. d. Focal CK19 positivity. DAB, ×400. e. CD34 negativity. DAB, ×400. (f) BCL-2 positivity. DAB, ×400. g. Calponin positivity. DAB, ×400. h. MIC2 positivity. DAB, ×400. i. Diffuse transducin-like enhancer of split 1 (TLE1) positivity, DAB, ×200, reinforcing a diagnosis of monophasic synovial sarcoma|
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|Figure 7: RT-PCR results in agarose gel electrophoresis in a suspected case of synovial sarcoma. Positive band in lane 4 (arrow), against a positive control (PC) for designed primers for SYT-SSX, of 331 bp size in lane 8, confirming a diagnosis of synovial sarcoma|
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|Figure 8: Round cell tumors. Ewing sarcoma (a-c). (a) Small round cells with focal rosetting arrangement. H and E, x400. (b) Diffuse CD99/MIC2 positivity. DAB, x400. (c) Diffuse Fli1 positivity. DAB, x400. Rhabdomyosarcoma (d-f). (d) Malignant round cell tumor in the alveolar pattern. H and E, x400. (e) Diffuse desmin positivity. DAB, x400. (f) Diffuse myogenin positivity. DAB, x400. DSRCT (g-k). (g) Nests of malignant round cells in desmoplastic stroma. H and E, x200. (h) CK/MNF116 positivity. DAB, x200. (i) Focal synaptophysin positivity. DAB, x200. (j) WT1 positivity (nuclear). DAB, x400. (k) Desmin positivity. DAB, x200|
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|Figure 9: Fluorescence in-situ hybridization (FISH) test for EWSR1 gene rearrangement at 22q11 (a) Intact or fused orange and green signals in both the allelic pairs, shown by arrows, indicate lack of EWSR1 rearrangement. DAPI, ×1000. (b) Split/break apart signals in tumor nuclei, shown by double lines, indicative of presence EWSR1 gene rearrangement, in a case of Ewing sarcoma. DAPI, ×1000|
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|Figure 10: (a) Classical gastrointestinal stromal tumor (GIST) composed of fascicles of spindly cells. H and E, ×200. (b) Diffuse CKIT/CD117 positivity. DAB, ×400. (c) Malignant epithelioid GIST (misdiagnosed as adenocarcinoma, on fine-needle aspiration cytology). H and E, ×400. (d) CKIT positivity. DAB, ×400. (e) Diffuse DOG1 positivity. DAB, ×400|
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Often, the time spent during grossing influences or is inversely proportional to time spent during reporting. Essentials of a histopathological report include all the parameters, including subtyping and classification of the lesion; marginal status in case of a resected soft tissue sarcoma, and parameters regarding its further prognostication. Molecular pathology should be actively included in the diagnosis of soft tissue tumors. It is desirable that the molecular result related to the diagnosis of a sarcoma is included in the report. Immunohistochemical staining and molecular results should be interpreted in a clinicopathological context. The value of MDT in soft tissue sarcoma, especially with regards to diagnosis and management, cannot be overemphasized.
We would like to thank immunohistochemistry laboratory and division of molecular pathology and translational medicine, Tata Memorial Hospital, Mumbai.
We also thank all members of the Multidisciplinary group of our respective insitu tions.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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