# Papillary renal cell carcinoma with extensive spindle cell foci: mimicker of mucinous tubular and spindle cell carcinoma

## TL;DR

This paper presents a rare case of a kidney tumor that resembles two different types of cancer, highlighting the importance of detailed testing for accurate diagnosis.

## Contribution

The case demonstrates the diagnostic challenge of distinguishing PRCC from MTSCC based on overlapping histological features.

## Key findings

- The tumor showed features of both PRCC and MTSCC, including a shaggy luminal surface and psammoma bodies.
- Immunohistochemistry and genomic analysis were essential to confirm the diagnosis as PRCC.
- E-cadherin absence and strong CD10 expression supported the PRCC diagnosis.

## Abstract

Papillary renal cell carcinoma (PRCC) is the second most common renal cell carcinoma (RCC), accounting for 10-15% of cases. Mucinous tubular and spindle cell carcinoma (MTSCC), on the other hand, accounts for only 1% of renal tumors and has a more favorable prognosis compared to PRCC. We report a 75-year-old female with a left upper pole solid renal mass displaying features of both papillary renal cell carcinoma (PRCC) and mucinous tubular and spindle cell carcinoma (MTSC). In this case, a shaggy luminal surface, multiple papillations, and psammoma bodies, absence of E-cadherin expression, and strong CD10 expression favored PRCC. Both immunohistochemistry and genomic analysis are critical to diagnose and differentiate tumors that may have overlapping features accurately.