• Rare (< 1% of kidney cancers) aggressive carcinoma of renal medulla arising from the principal cells of the distal collecting ducts of Bellini
• Morphology: irregular, infiltrating tubules with high grade cells often containing mucin; marked stromal desmoplasia and inflammatory infiltrate
• Essentially a diagnosis of exclusion (Am J Surg Pathol 2020;44:e47)

• Collecting duct carcinoma (preferred)
• Bellini duct carcinoma or carcinoma of the collecting ducts of Bellini (historic name, discouraged)

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Contributed by Daniel Anderson, M.D., M.B.A. and Debra L. Zynger, M.D.


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Contributed by Daniel Anderson, M.D., M.B.A. and Garrison F. Pease, M.D.

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• Metastatic carcinoma, including from GI or lung:
  • Usually, well defined borders; multiple foci may be present
  • Clinical history and radiologic review could be helpful
  • Immunohistochemistry may be helpful in excluding a metastasis
• Urothelial carcinoma showing glandular differentiation:
  • Usually associated with prior history of lower tract urothelial carcinoma
  • Filling defect on imaging, positive urine cytology
  • If located in renal calyces or pelvis it would favor urothelial carcinoma; however, involvement of cortex is found in higher stage disease
  • Location of in situ urothelial carcinoma or residual papillary component is helpful
    • Carcinoma in situ (CIS) may be present in renal pelvis
    • CIS can colonize the collecting ducts with solid nests as opposed to dysplastic glandular cells in collected duct carcinoma
    • Careful sampling of renal pelvis recommended
  • Usually, lower stage disease at presentation
  • Urothelial carcinoma typically p63+ / GATA3+ / uroplakin II+ and negative for PAX8 (Am J Surg Pathol 2010;34:965, Hum Pathol 2013;44:2651)
    • However, a subset of upper tract urothelial carcinoma may show PAX8 positivity (usually weaker) and sensitivity for GATA3 and p63 are less than 100%, particularly in high grade tumors
• Fumarate hydratase (FH) deficient renal cell carcinoma / hereditary leiomyomatosis RCC:
  • Often viral inclusion-like (CMV-like) macronucleoli with perinucleolar halos are seen
  • Tubulocystic and intracystic papillary with or without hyalinization patterns may favor FH deficient RCC (Am J Surg Pathol 2018;42:279)
  • Loss of fumarate hydratase, nuclear and cytoplasmic expression of 2SC
  • In one study, 25% of cases diagnosed previously as collecting duct carcinoma were reclassified as fumarate hydratase deficient renal cell carcinoma using fumarate hydratase and 2SC IHC (Am J Surg Pathol 2018;42:279)
• Papillary renal cell carcinoma:
  • More well circumscribed, predominantly papillary, often psammoma bodies and foamy macrophages within papillae; usually no angiolymphatic invasion, no desmoplasia or inflammation, no dysplasia of collecting duct epithelium
  • CEA-, HMWCK-, Ulex europaeus-, AMACR+, CD10+, trisomy 7 and 17 (Hum Pathol 2008;39:1350)
• SMARCB1 deficient renal medullary carcinoma (Am J Surg Pathol 2014;38:871):
  • Occurs in those with sickle trait or related hemoglobinopathies; sickled RBCs (drepanocytes) may be found within tumor (Transl Androl Urol 2021;10:1506)
    • Distinction from collecting duct not possible on morphologic grounds alone
  • Sieve-like / cribriform and reticular / yolk sac tumor-like patterns favor renal medullary (Am J Surg Pathol 2018;42:279)
  • Both positive for PAX8; p63 and GATA3 usually negative
  • Inactivation of tumor suppressor gene INI1 on long arm of chromosome 22 is frequently detected
  • INI1 negative (loss) and OCT 3/4 positive in 50% of cases (Urology 2011;78:474.e1, Histopathology 2012;61:428, Am J Surg Pathol 2018;42:279)
• Mucinous tubular spindle cell carcinoma with high grade transformation
• Tubulocystic carcinoma:
  • Often detected incidentally and usually without pain, hematuria, flank mass, etc.
  • Cortical with involvement of medullary region at times
  • Well circumscribed with multilocular sponge-like appearance without necrosis or hemorrhage (versus more solid appearance of collecting duct)
  • Consists of tubules and variable sized cysts; should not display infiltrative glands, cords, solid sheets, necrosis, hemorrhage and desmoplastic stroma that is relatively common in collecting duct carcinoma
  • Less mitotically active
  • Will not have dysplastic medullary collecting duct structures or extension into perirenal adipose tissue
• If the size of the tumor obscures the site of origin, infiltrative growth that extends between normal structures, such as glomeruli and tubules, can be seen as a clue that the tumor is medullary based
  • This pattern can be seen in collecting duct carcinoma, medullary carcinoma and invasive urothelial carcinoma; similar patterns can also be seen in metastatic tumors and lymphoma (Surg Pathol Clin 2015;8:587)

A 76 year old man with history of noninvasive low grade papillary urothelial carcinoma undergoes a nephrectomy for a 5 cm centrally located urothelial mass involving the renal pelvis, medulla and cortex. Photomicrographs are shown of the invasive component and results of renal pelvis sampling. Which of the following is true regarding this neoplasm?

1. Has a multilocular, sponge-like cut surfaces on gross examination
2. May show aneuploidy in chromosome 3, 7 or 17 or loss of 9p21 locus
3. Will often demonstrate loss of fumarate hydratase by immunohistochemistry
4. Will often show positive immunohistochemical expression for PAX8 and negative for p63 and GATA3

B. May show aneuploidy in chromosome 3, 7 or 17 or loss of 9p21 locus. The findings support the diagnosis of invasive urothelial carcinoma with glandular differentiation. The clinical history and demonstration of a noninvasive high grade papillary component in the renal pelvis supports the diagnosis. Urothelial carcinoma often demonstrates aneuploidy in chromosomes 3, 7 or 17 or loss of 9p21 locus, which is the basis for the UroVysion FISH assay. The criteria for positivity on UroVysion is ≥ 4 of 25 morphologically abnormal cells showing a gain of ≥ 2 chromosomes in the same cell or ≥ 12 of the 25 cells having a loss of 9p21. Urothelial carcinomas will be positive for p63, GATA3 and negative for PAX8 (as opposed to renal cell carcinomas). They will demonstrate retained fumarate hydratase (as opposed to fumarate hydratase deficient RCC). A multilocular sponge-like cut surface on gross evaluation is characteristic of tubulocystic renal cell carcinoma.

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Reference: Collecting duct carcinoma

A 59 year old man is diagnosed with collecting duct carcinoma. Which of the following is true regarding this entity?

1. Has no morphologic overlap with fumarate hydratase deficient
2. Has prominent stromal desmoplasia, infiltrative growth and inflammatory cell reaction
3. Is correlated with sickle cell trait
4. Will show papillary growth with foamy macrophages in papillae

B. Has prominent stromal desmoplasia, infiltrative growth and inflammatory cell reaction. Collecting duct carcinoma (CDC) often presents with advanced disease over a wide age range and with male predominance. The carcinoma arises from the principal cells of the distal collecting ducts of Bellini and often shows a multinodular, infiltrative growth pattern of cords, tubules, tubulopapillary, nested, solid or sheet-like growth with high grade nuclei and associated inflammatory reaction. The presence of papillary growth in CDC can raise the differential of papillary renal cell carcinoma; however, the latter will show typical papillary morphology, including foamy macrophages within papillae. CDC has morphologic overlap with fumarate hydratase deficient renal cell carcinoma. In one study, 25% of cases of CDC were reclassified to fumarate hydratase deficient renal cell carcinoma using fumarate hydratase and 2SC IHC stains. CDC is morphologically similar to medullary carcinoma. Renal medullary carcinoma usually presents in younger patients with sickle cell trait or hemoglobin SC disease; few have sickle cell disease. Renal medullary carcinoma usually demonstrates loss of SMARCB1 (also known as INI1, SNF5 or BAF47).

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Reference: Collecting duct carcinoma