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.


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

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.

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John Hedgepeth
Sara E. Wobker
University of North Carolina School of Medicine
Chapel Hill, North Carolina


Kidney, tubulocystic, carcinoma