High-grade adenocarcinoma (gland forming) believed to arise from collecting duct epithelial cells.
Often centered in medullary region of the kidney with white or gray cut surfaces and central necrosis is common.
Demonstrates infiltrative borders. (In contrast to most RCC; this feature is also typical for urothelial carcinoma and metastatic tumors to kidney)
Variable but usually has infiltrative glandular/tubular or papillary architectures (image A) & (image B).
Presence of desmoplastic stroma. (In contrast to most RCC)
High-grade cytology with abundant mitosis.
"Hobnail" appearance of the cells lining (when you can find it).
Aggressive, frequently presents with higher stage or metastasis.
~1/2 of patients dead of disease in 2 years.
Papillary RCC: also has papillae but with histiocytes and is rarely infiltrative or desmoplastic; AMACR+, CK7+ and HMWK-.
Urothelial CA: distinction becomes difficult if it has glandular differentiation; look for sheets of typical urothelial carcinoma.