Prognosis
The five-year survival rate of PRCC has been reported as 82-90%, which is slightly higher than that of other kidney cancers. The reduced survival rate has been positively correlated to several factors, which are high nuclear grade and stage, vascular invasion, DNA aneuploidy, and more. Patients with type 1 PRCC have significantly improved survival rates than those with type 2, which is a reflection of its lower TNM stage with a well-encapsulated tumor. Compared to other common types of RCC, PRCC exhibits a relatively lower risk of tumor recurrence and cancer-related death after nephrectomy. Specifically, the cancer-specific survival rate at five years following surgery with PRCC has reached up to 91%, while clear cell RCC and chromophobe RCC were 72% and 88%, respectively. Epidemiology
Among different histologic subtypes of RCC, PRCC is the second most predominant type and accounts for 10-15% of all renal tumors. In the case of the United States, it is estimated that the incidence of PRCC will rise to 3,500 to 5,000 cases annually. Generally, PRCC is more prevalent among men than women, while the reported sex ratio (M: F) varies from 1.8:1 to 3.8:1. The mean age at presentation is identified as 52–66 years old; however, no statistically significant difference was found in the incidence of PRCC between the younger (< 40 years) and older adult groups (>40 years). In terms of racial variation, several studies have proven that people with African or Afro-Caribbean ancestry tend to have higher chances of being diagnosed with PRCC.
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.