This is a case of pleomorphic sarcomatoid carcinoma of renal cell origin.

The patient underwent CT-guided biopsies of the mass. Pathology demonstrated pleomorphic epithelioid to focally spindled malignant large cells with abundant eosinophilic cytoplasm and prominent macronucleoli. The cells formed sheets. There was a suggestion of papillary or pseudopapillary arrangements. The tumor cells were diffusely and strongly positive for PAX-8, MNF-116, and vimentin, while having focal equivocal weak staining for RCC and carbonic anhydrase 9. Further immunohistochemical staining revealed the tumor was positive for Cam-5.2, MNF-116, PAX-8, and MITF. The morphology and immunohistochemical stain profile support the diagnosis of sarcomatoid carcinoma of renal origin.

The patient was scheduled for aggressive local therapy with external beam radiotherapy. Repeated imaging showed spinal metastasis. The biopsy result of this mass was consistent with the primary tumor.

This tumor appeared distinct from both the adrenal gland and kidney. There have been published cases of pleomorphic sarcomatoid carcinoma, primarily arising from the adrenal gland(s) and peritoneum. However, the pathology was suggestive of a renal origin. The histopathologic specimens were sent to other institutions for validation, which agreed that the histology favors renal cell origin. While rare, there are case reports of renal cell carcinoma arising as a metastatic focus without an identifiable renal primary ^1-3.

Co-authors:
Michael Schuster, MD
Christine Cooley, MD