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.

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.

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