Case of the Week

2019-19 / JUNE 24 (CONTRIBUTOR: CARLA L. ELLIS)

CASE HISTORY

A 69 year old male presented with a 9.2 cm well circumscribed renal mass .

Click on the below thumbnails to enlarge photos.

Quiz

What is the correct diagnosis?

a. Sarcomatoid Renal Cell Carcinoma

b. Mucinous Tubular and Spindle Cell Carcinoma

c. “Fat poor” Angiomyolipoma

d. Synovial sarcoma

e. Metanephric adenoma

Mucinous tubular and spindle cell carcinoma is a renal epithelial neoplasm characterized by the components of its name: a myxoid stroma (mucinous) with tubular epithelial formations (tubular) merging with bland spindle cells (and spindle cell carcinoma). It is rare, accounting for <1% of all renal neoplasms, with a mean age of 58 years and a female to male predilection of 3:1. This case was unusual as it occurred in a 69 year old male and was 9.2 cm in size.
The tumor consists of bland tubular structures that can be elongated or anastomosing with transition to spindle cells. The tubular component is usually cuboidal and may focally show clear cells, oncocytic change or cytoplasmic vacuolization. Rare tumors with high grade nuclei and sarcomatoid change have been described. Most commonly, the stroma has a basophilic appearance with a bubbly quality and can show admixed chronic inflammatory cells and intense staining with Alcian Blue (see photos). The tumors are immunohistochemically positive for CK7, Pax2 and AMACR, making them difficult to differentiate from papillary renal cell carcinoma; however the genomic signature of +7, +17 and loss of chromosome Y (papillary renal cell carcinoma) is not shared with mucinous tubular and spindle cell carcinoma.
Sarcomatoid renal cell carcinoma is highly pleomorphic and diffusely infiltrative. Angiomyolipoma has a very distinct immunohistochemical profile, reacting with HMB45 and other melanoma markers. Metanephric adenoma is positive for WT1 and CD57 and negative for CK7 and AMACR. Synovial sarcomas can show mono- or biphasic architecture with the characteristic chromosomal translocation t(X; 18) (p11; q11) involving genes SS18 and either SSX1, SSX2 or SSX4.
Most tumors have an indolent course and recurrence/metastasis is rare, however, high grade transformation has been reported with a poor outcome.

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