Fig. 3

Renal cell carcinomas with papillary features and some of their differential diagnoses. Type 1 Papillary RCC exhibits papillae lined by a single layer of cells with scant pale cytoplasm and low nucleolar grade. Foamy macrophages within fibrovasculares cores are a common finding (a HE, 100x). Type 2 Papillary RCC displays nuclear pseudostratification with cells containing voluminous eosinophilic cytoplasm and generally high nucleolar grade. In this case, such nucleolar prominence imposes further evaluation to exclude fumarate hydratase deficiency (b HE, 100x). Mucinous tubular and spindle cell carcinoma consists of tightly packed tubular component lined by cuboidal cells that transitions into a bland spindle cell component, set in a variable amount of mucinous / myxoid stroma (c HE, 100x). Papillary adenoma shows identical architectural and cytologic features to classic type 1 PRCC but the diagnosis required low nuclear grade, absent fibrous capsule and size ≤15 mm (d HE, 100x). Collecting duct carcinoma consists in a high-grade adenocarcinoma that usually show tubular morphology, and highly infiltrative growth with associated desmoplastic reaction (e HE, 40x). Medullary carcinoma – solid areas of highly infiltrative high-grade carcinoma inducing desmoplastic reaction in renal cortex – note preexistent tubules and glomerulus intermixed with the infiltrative tumor. This was an advanced stage RCC diagnosed in a 25-year-old female patient with sickle cell anemia (f HE, 100x)