Case of the Week

2021-44/November 1

Contributors: John Hedgepeth and Sara E. Wobker

A man in his 40s with end stage renal disease, status post living donor kidney transplant for IgA nephropathy in his 20s, underwent a radical nephrectomy for an incidentally discovered, contrast-enhancing, solid, interpolar mass of his native left kidney.

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6 photo(s) Updated on: October 30, 2021

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Quiz

1. What is the correct diagnosis?

A. Collecting duct carcinoma

B. Tubulocystic renal cell carcinoma

C. Papillary renal cell carcinoma, tubulocystic variant

D. Acquired cystic disease-associated renal cell carcinoma

E. Multilocular cystic renal neoplasm of low malignant potential

Tubulocystic renal cell carcinoma (TRCC) is a rare, usually indolent renal malignancy composed of small to medium-sized tubules with variable amounts of cystic dilatation (Figure 1). Originally thought to be a form of collecting duct carcinoma, TRCC is now considered to represent a pathologically and clinically distinct entity with low metastatic potential. As many as 60% of these tumors are discovered incidentally,and they show a male predominance (7:1), as well as a predilection for the left kidney (70%).

Grossly, TRCC often appears as a single well-circumscribed, unencapsulated mass within the renal cortex and/or medulla. The mass will often show a “bubble-wrap” appearance due to the numerous cystically dilated tubules containing serous fluid. Histologically, the tumor shows a proliferation of tubules and cysts lined by a single layer of flat, cuboidal/columnar, or hobnail epithelium (Figure 2); the epithelial cells may also show abundant eosinophilic, oncocytoma-like cytoplasm. The stroma surrounding the tubules is typically hypocellular and fibrotic. The neoplastic cells show enlarged, round nuclei with prominent nucleoli usually classified as ISUP grade 3; mitoses are infrequent (Figure 3).

TRCC is frequently immunoreactive for cytokeratins CK8, CK18, and CK19, while being less frequently positive for CK7. The tumor in this case shows only focal CK7 positivity in a single tubule. The tumor cells also usually stain positive for markers associated with the proximal convoluted tubules (CD10, P504S/AMACR). Because fumarate hydratase (FH) deficient renal cell carcinomas can show tubulocystic features, retained positive staining for FH supports a diagnosis of TRCC and excludes the more aggressive and potentially syndrome-associated FH-deficient RCC.

Amin MB, MacLennan GT, Gupta R, Grignon D, Paraf F, Vieillefond A, Paner GP, Stovsky M, Young AN, Srigley JR, Cheville JC. Tubulocystic carcinoma of the kidney: clinicopathologic analysis of 31 cases of a distinctive rare subtype of renal cell carcinoma. Am J Surg Pathol. 2009 Mar;33(3):384-92.

Chen YB, Brannon AR, Toubaji A, Dudas ME, Won HH, Al-Ahmadie HA, Fine SW, Gopalan A, Frizzell N, Voss MH, Russo P, Berger MF, Tickoo SK, Reuter VE. Hereditary leiomyomatosis and renal cell carcinoma syndrome-associated renal cancer: recognition of the syndrome by pathologic features and the utility of detecting aberrant succination by immunohistochemistry. Am J Surg Pathol. 2014 May;38(5):627-37

Sarungbam J, Mehra R, Tomlins SA, Smith SC, Jayakumaran G, Al-Ahmadie H, Gopalan A, Sirintrapun SJ, Fine SW, Zhang Y, Amin MB, Reuter VE, Chen YB, Tickoo SK. Tubulocystic renal cell carcinoma: a distinct clinicopathologic entity with a characteristic genomic profile. Mod Pathol. 2019 May;32(5):701-709.

Smith SC, Trpkov K, Chen YB, Mehra R, Sirohi D, Ohe C, Cani AK, Hovelson DH, Omata K, McHugh JB, Jochum W, Colecchia M, Amin M, Divatia MK, Hes O, Menon S, Werneck da Cunha I, Tripodi S, Brimo F, Gill AJ, Osunkoya AO, Magi-Galluzzi C, Sibony M, Williamson SR, Nesi G, Picken MM, Maclean F, Agaimy A, Cheng L, Epstein JI, Reuter VE, Tickoo SK, Tomlins SA, Amin MB. Tubulocystic Carcinoma of the Kidney With Poorly Differentiated Foci: A Frequent Morphologic Pattern of Fumarate Hydratase-deficient Renal Cell Carcinoma. Am J Surg Pathol. 2016 Nov;40(11):1457-1472.

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