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J Cutan Pathol. 2017 Oct;44(10):874-877. doi: 10.1111/cup.12998. Epub 2017 Jul 24.

Metastatic sarcomatoid renal cell carcinoma manifesting as a subcutaneous soft tissue mass.

Author information

1
Department of Pathology, Medical College of Wisconsin, Milwaukee, Wisconsin.
2
Department of Dermatology, Section of Dermatopathology, Medical College of Wisconsin, Milwaukee, Wisconsin.

Abstract

Metastases from visceral malignancies to subcutaneous soft tissues are relatively rare and their diagnosis requires a high level of suspicion. It is even more challenging if a metastatic lesion shows non-specific high-grade spindle cell morphology overlapping with various primary cutaneous and soft tissue tumors. We describe a unique case of subcutaneous metastasis of sarcomatoid renal cell carcinoma which was the first manifestation of the occult malignancy. The patient had a history of lipomas and dysplastic nevi and presented with an upper back mass. The mass, located superficially within the subcutis, was composed of atypical spindle cells arranged in a storiform pattern. By immunohistochemistry, the tumor cells were strongly diffusely positive for cytokeratin AE1/AE3 and vimentin and negative for Melan-A, S-100 protein, SOX10, melanoma cocktail, epithelial membrane antigen (EMA), p63, CK7, CK18, CK20, smooth muscle actin (SMA), desmin, CD34, TTF-1, CD21, CD99 and bcl-2. Scattered tumor cells were positive for MDM2 immunostain, but MDM2 amplification was not detected using fluorescent in situ hybridization (FISH). Co-expression of cytokeratin and vimentin by the tumor raised the possibility of metastatic renal cell carcinoma and positivity of the tumor for PAX8 supported this hypothesis. A large renal mass was detected radiologically and the subsequent nephrectomy specimen showed high-grade clear cell renal cell carcinoma with sarcomatoid features.

KEYWORDS:

sarcomatoid renal cell carcinoma; spindle cell lesion; subcutaneous soft tissue metastasis

PMID:
28675457
DOI:
10.1111/cup.12998
[Indexed for MEDLINE]

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