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LETTER TO THE EDITOR
Year : 2022  |  Volume : 59  |  Issue : 3  |  Page : 433-435
 

Renal angiomyoadenomatous tumor in young man a rare entity


1 Department of Urology, All India Institute of Medical Sciences, New Delhi, India
2 Department of Pathology, PGIMER, ABVIMS, RML Hospital, New Delhi, India
3 Department of Radiology, All India Institute of Medical Sciences, New Delhi, India
4 Department of Pathology, All India Institute of Medical Sciences, New Delhi, India

Date of Submission12-Apr-2020
Date of Decision23-Jun-2020
Date of Acceptance25-Jul-2020
Date of Web Publication12-Oct-2022

Correspondence Address:
Adarsh Barwad
Pathology, All India Institute of Medical Sciences, New Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijc.IJC_327_20

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How to cite this article:
Nayak B, Phulware RH, Dhamija E, Barwad A. Renal angiomyoadenomatous tumor in young man a rare entity. Indian J Cancer 2022;59:433-5

How to cite this URL:
Nayak B, Phulware RH, Dhamija E, Barwad A. Renal angiomyoadenomatous tumor in young man a rare entity. Indian J Cancer [serial online] 2022 [cited 2022 Dec 7];59:433-5. Available from: https://www.indianjcancer.com/text.asp?2022/59/3/433/358397




Dear Editor,

Renal angiomyoadenomatous tumour (RAT) is a newly described rare neoplasm with distinctive histopathological appearance and is characterized by leiomyomatous stroma often forming abortive vascular structures surrounding and encasing a distinctive epithelial component with basophilic or clear cytoplasm.[1],[2] This tumor is morphologically and genetically different from clear cell renal cell carcinoma (ccRCC). Although reported in the pathology literature, to our knowledge, very few prior case reports have described its histomorphology and immunohistochemistry.[3],[4],[5]

The patient was a 36-year-old man who presented with right flank pain with off and on hematuria and on computed tomography (CT) [Figure 1], a right renal cystic mass was detected. The patient underwent right radical nephrectomy. On gross the right kidney was measuring 9.5 cm × 5 cm × 4 cm with attached ureter 2.5 cm in length. On serial slicing renal capsule was intact and multiple non communicating cysts varying in size from 1.2 to 3.6 cm with intervening solid fleshy areas [Figure 2] was seen in the kidney. Cysts were lying at a distance of 0.1 cm from the nearest overlying capsule and 3 cm from resected margin of the ureter. Microscopic examination showed a tumor composed of an admixture of epithelial component and prominent leiomyomatous stroma with interconnecting vascular channels [Figure 2]. Epithelial components showed tubule formation with cells exhibiting a moderate amount of cytoplasm and apical snouting. This component was immunopositive for pancytokeratin (CK) while negative for Wilm's tumor protein (WT-1). Stromal component showed the formation of smooth muscle bundles that are immunopositive for smooth muscle actin (SMA) while negative for CD34, estrogen and progesterone receptor (ER and PR), S100, HMB45, and melan-A. Histomorphological and immunohistochemical staining pattern of the present case was similar to the previously reported cases of RAT.
Figure 1: Right renal mass. Multiphase contrast enhanced CT scan shows a heterogeneous mass in right kidney (asterisk) which shows solid (black asterisk) as well as cystic (white asterisk) components. The solid component shows intense enhancement on arterial phase (a) with persistent enhancement similar as renal parenchyma on venous and excretory phase (asterisk in b and c). The mass extends into renal pelvis (arrow in c); however without hydronephrosis and no extension into either renal veins (arrows in d)

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Figure 2: Right Nephrectomy specimen showing a tumor in the upper pole with multiple cystic spaces and a normal renal parenchyma at lower pole (Blue arrow) (a), Microscopic images showing a tumor composed of epithelial component with tubule formation and having apical snouting (b and c), along with stromal component demonstrating leiomyomatous areas (Red arrow) (d). Stromal tumour component strongly immunopositive for smooth muscle actin (SMA) (e) and Desmin (f)

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Advances in diagnostic pathology with the implementation of the molecular study, have helped to add many new tumor entities into the current classification of renal tumors. RAT is a newly described renal neoplasm which has not yet been included in the classification of renal tumors. The first case of RAT was reported in 2000 by Michael et al. who later published the largest reported series of 5 cases in 2009.[1],[2],[6]

RAT is a rare neoplasm. Unlike our case, most RATs have been described in adult men in their fifth to sixth decade, except the index case, which was described in a 93-year-old man. The tumors are either discovered incidentally in radiographic studies or the patients present with flank pain and painless hematuria. Unlike other renal tumors, RATs have not been observed in association with syndromes such as von Hippel-Lindau or tuberous sclerosis.[1],[2],[5]

Histologically, it is different from the usual renal neoplasms included in the present World Health Organization (WHO) classification of renal tumors such as ccRCC, papillary RCC, and chromophobe RCC. Benign renal cysts form an important differential diagnosis of renal neoplasms because cystic changes are very common in the latter. Because most renal neoplasms are managed by partial or radical nephrectomy, whereas benign cysts, unless symptomatic, can be managed conservatively.[1],[7]

On gross examination, RAT is seen as a well-circumscribed mass of solid tumors with microcystic areas and grayish or tan to light brown color and is limited to renal parenchyma; however, one case with marked cystic changes have been reported in the series published by Michael et al. The longest diameter of the tumor range from 2.3 to 8.5 cm with a median diameter of 4.1 cm.[1],[4],[8] The case reported here was almost entirely cystic with focal mural nodules. The tumors vary in size (mean, 4.1 cm) and have a variably thick but distinct capsule. Focal areas of hemorrhage may be present; however, grossly evident necrosis has not been reported. These tumors have not been reported to involve the renal pelvis, renal vessels, or adrenal gland.[1],[2],[7]

The epithelial tissue, represented by adenomatous structures, composed of cells with small deeply basophilic nuclei, often in a linear arrangement reminding of small beads on a string. The nuclei of the neoplastic cells are usually of equal size and small. Sometimes the glandular structures are distended with deeply eosinophilic colloid with “moth-eaten” peripheral areas. In the well-formed tubular or branching structures, the nuclei are seen close to the basal membrane. There exists a relationship between a capillary network and the epithelial component of every single adenomatous structure of RAT, whether in the solid, tubular, or clear cell areas. The capillaries are seen intimately surrounding the circumference of the basal membrane of all adenomatous structures.[1],[2],[7]

RAT does not show atypia or mitoses. The stromal muscular component formed by eosinophilic bundles and strands of leiomyomatous tissue composed of elongated cells with cigar-shaped nuclei. The leiomyomatous stroma grows inside the tumors among the epithelial component, and in addition, variously thick bands of leiomyomatous tissue encircled the whole tumors, forming a continuous capsule.[1],[6]

Immunohistochemically, the epithelial component of these tumors shows positivity with all antibodies to cytokeratins AE1-AE3, CAM 5.2, CK 7, and CK 20. CK7 is more strongly positive compared with CK20. In addition to CK positivity, the epithelial component shows strong positivity for epithelial membrane antigen (EMA) and vimentin. Epithelial components are usually negative for CD10, HMB45 and Melan A. Carbonic anhydrase IX antibody can show positivity in the epithelial component and negative in the leiomyomatous component. The stromal leiomyomatous component shows strong positivity with antibodies to caldesmon, calponin, vimentin, and smooth muscle actin; while negative with HMB45, Melan A, and tyrosinase. The endothelial cells of the capillary network are positive for FVIII and CD34. The proliferative index (MIB1) generally very low and always less than 1% of the cells reacted positively.[1],[2],[3],[4],[6]

It remains controversial whether RAT should be considered as a variant of clear cell (tubulo) papillary RCC. There is evidence that clear cell (tubulo) papillary RCCs with or without ESRD and RATs come under the spectrum of the same category of tumors. For example, Deml et. al.[8] studied 27 clear cell (tubulo) papillary RCC and 7 RAT cases using histology, immunohistochemistry, and molecular assays. They found that clear cell (tubulo) papillary RCC and RAT were indistinguishable on the grounds of morphology, immunostain markers, and molecular changes.[3],[4],[5]

Kuroda N et al.[5] showed that RAT is characterized by monosomy of chromosomes 1, 11 and 16 on FISH. RAT genetically shows neither Von Hippel-Lindau syndrome (VHL) gene mutation nor 3p loss of heterozygosity. These results have elucidated that RAT is histologically and genetically a distinct entity from previously established diseases including RCC with leiomyomatous stroma and mixed epithelial and stromal tumor.[4],[5],[6],[7] In the present case, molecular testing was not done.

In conclusion, RAT is an unusual neoplasm and pathologists and clinicians should be aware of the presence of ccRCC histologically mimicking RAT and is characterized by mixed epithelial and mesenchymal elements (capillaries and smooth muscle stroma) that may be cystic or solid and has imaging findings that overlap with those of other renal neoplasms. Whenever pathologists encounter such tumors having annoying histological features, they should correctly diagnose these tumors with systemic examinations containing macroscopic, histological, and immunohistochemical studies. Although the experience with this tumor is limited both by the number of reported cases and duration of follow-up, its clinical behavior appears to be favorable. More experience with this tumor is needed to determine whether it represents a low-grade malignancy or a benign neoplasm and whether it shows any characteristic cytogenetic abnormalities.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Michal M, Hes O, Nemcova J, Sima R, Kuroda N, Bulimbasic S, et al. Renal angiomyoadenomatous tumor: Morphologic, immunohistochemical, and molecular genetics study of a distinct entity. Virchows Archiv 2009;454:89-99.  Back to cited text no. 1
    
2.
Jayalakshmy PS, Jose M, Feroze M, Kumar RK. Renal angiomyoadenomatous tumour. Turk J Urol 2017;43:378-82.  Back to cited text no. 2
    
3.
Aron M, Chang E, Herrera L, Hes O, Hirsch MS, Comperat E, et al. Clear cell-papillary renal cell carcinoma of the kidney not associated with end-stage renal disease. Am J Surg Pathol 2015;39:873-88.  Back to cited text no. 3
    
4.
Kuroda N, Hosokawa T, Michal M, Hes O, Sima R, Ohe C, et al. Clear cell renal cell carcinoma with focal renal angiomyoadenomatous tumor-like area. Anna Diagn Pathol 2011;15:202-6.  Back to cited text no. 4
    
5.
Kuroda N, Michal M, Hes O, Taguchi T, Tominaga A, Mizobuchi K, et al. Renal angiomyoadenomatous tumor: Fluorescence in situ hybridization. Pathol Int 2009;59:689-91.  Back to cited text no. 5
    
6.
Michal M, Hes O, Havlicek F. Benign renal angiomyoadenomatous tumor: A previously unreported renal tumor. Anna Diagn Pathol 2000;4:311-5.  Back to cited text no. 6
    
7.
Singh C, Kendi AT, Manivel JC, Pambuccian SE. Renal angiomyoadenomatous tumor. Anna Diagn Pathol 2012;16:470-6.  Back to cited text no. 7
    
8.
Deml KF, Schildhaus HU, Comperat E, von Teichman A, Storz M, Schraml P, et al. Clear cell papillary renal cell carcinoma and renal angiomyoadenomatous tumor: Two variants of a morphologic, immunohistochemical, and genetic distinct entity of renal cell carcinoma. Am J Surg Pathol 2015;39:889-901.  Back to cited text no. 8
    


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