Classification
In 2014, PRCC was first acknowledged as a renal tumor subtype by the World Health Organization (WHO) considering its distinct genetic, molecular and histologic characteristics. It is further divided into type 1 and type 2 based on morphological features. Type 1 Papillary Renal Cell Carcinoma
Type 1 PRCC, also known as a renal tumor caused by a genetic predisposition of hereditary papillary renal cancer syndrome, compromises approximately 25% of all PRCCs. In the perspective of immunochemistry, it has a profile of strong CK7 and alpha-methyl acyl-CoA racemase (AMACR) expression at most focal CA-IX expression. Histologically, its epithelium is composed of relatively small-sized simple cuboidal cells lined in a single layer. These cells are well-characterized by basophilic cytoplasm. Due to its solid growth, an extremely compact papillary architecture is often observed. Other morphological characteristics include intracellular hemosiderin and foamy macrophages placed inside of papillary fibrovascular cores or psammoma bodies. In general, the nuclei of type 1 PRCC belong to grade 1-2 of the Fuhrman system. Type 2 Papillary renal cell carcinoma
Accounting for 25% of PRCCs, type 2 PRCC is the pathological subtype that is most commonly associated with hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome. When compared to type 1, it shows more variation in protein expression mostly by loss of CK7. In a gross examination, it shows papillae covered by large cells abundant in eosinophilic cytoplasm. Its large spherical nuclei on papillary cores are arranged in a pseudo-stratified manner. Unlike type 1 PRCC, foamy macrophages and psammoma bodies are less common in case of type 2.
According to the National Cancer Database, PRCC was more common in the Non-Hispanic Black population (38.9%) when compared to other races – Asian American (18.0%), Non-Hispanic White (13.2%), and Hispanic White populations (6.1%). References


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