Collecting duct carcinoma (CDC) is a rare and aggressive renal epithelial neoplasm arising from the distal part of the collecting ducts (of Bellini) in the renal medulla.   Even nowadays, the diagnosis of CDC remains a diagnosis of exclusion.

More likely to occur in middle to old age population, more common in males and in black than in white patients, both with a 2:1 ratio.

Patient may present with abdominal pain, gross hematuria, weight loss and a flank mass.

Well-defined or ill-defined mass in the renal medulla involving renal sinus, with frequent extension into the renal pelvis.

Prominent interstitial growth pattern with preserved glomeruli and renal tubules with several solid sheets/cords/nests, tubulopapillary and infiltrating glandular pattern with small-sized or medium-sized elongated tubules infiltrating in a desmoplastic stroma.¹

SMARCB1(INI1) expression is retained; FH expression is retained, and OCT3/4 expression is completely negative.

Various chromosomal and genomic alterations have been reported with inconsistent results. DNA losses are frequent, e.g., 1q, 6p, 8p, 9p and 21q as well as loss of Y. ^2,3

Several genomic alterations were detected, being NF2 (29%), SETD2 (24%), SMARCB1 (18%), and CDKN2A (12%) the most common, suggesting a potential role for mTOR inhibitors in patients with NF2 alterations. ³

So far, there is no characteristic molecular genetic feature, or combination of features, useful for a definitive diagnosis. Molecular genetic testings should be considered after excluding other entities in the differential diagnosis (i.e., FH-deficient RCC, renal medullary carcinoma, papillary RCC). ^4-6

Of all renal cancers, CDC has the worst prognosis. Response to chemotherapy in CDC patients is modest to poor and overall survival is often less than 1 year.