Malignant Mesenchymal Renal Tumor: A Rare Case of Primary Renal Fibrosarcoma

Abstract

Malignant mesenchymal neoplasms of kidney constitute a rare group of tumors. Primary fibrosarcoma of kidney is an extremely rare subtype of primary malignant mesenchymal renal neoplasms. An elderly female presented with a gradually increasing abdominal lump and mild abdominal discomfort. On cross-sectional imaging, the lesion showed features suggestive of an atypical renal mass not conforming to either ball or bean type growth pattern. The mass was surgically removed and on histopathological and immunohistological investigations diagnosed to be primary renal fibrosarcoma.

Primary renal fibrosarcoma with local invasion into the mesenteric membrane of a mongrel dog

“…Fibrosarcoma is positive for vimentin and negative for cytokeratin and desmin [3,7]. However, sarcomatoid renal cell carcinomas and leiomyosarcoma are positive for cytokeratin and desmin [3,7]. In this case, the renal mass and the mesenteric membrane sample were positive for vimentin and were stained blue with Masson's trichrome staining, confirming fibrosarcoma [2].…”

“…Few cases of renal sarcomas, including spindle cell sarcomas, leiomyosarcoma, osteosarcoma, hemangioma, hemangiosarcoma, fibrosarcoma, oncocytoma, and giant cell tumors, are reported [1,2,8,12,13]. In humans, primary renal sarcomas contribute to only 1% to 3% of all renal tumors [3,7]. Canine renal neoplasms can be divided into four types according to the cellular origin: tubular or transitional cell origin, nephroblastic origin, mesenchymal origin, and nonepithelial origin [1,2].…”

“…The renal capsule consists of large amounts of fibrous and connective tissue; fibrosarcoma is usually known as originating from the renal capsule, as described herein [3,7]. By using immunohistochemical staining, fibrosarcoma and other types of sarcomas, especially leiomyosarcoma or sarcomatoid renal cell carcinoma, need to be differentiated [3,7].…”

“…In human medicine, primary renal fibrosarcoma is very rare and malignant; it is an aggressive tumor of the kidney with a very poor prognosis [3,7]. In dogs, fibrosarcoma usually has an oral origin (mandible) [4,5].…”

“…By using immunohistochemical staining, fibrosarcoma and other types of sarcomas, especially leiomyosarcoma or sarcomatoid renal cell carcinoma, need to be differentiated [3,7]. Fibrosarcoma is positive for vimentin and negative for cytokeratin and desmin [3,7].…”