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Man in his late forties with left renal mass
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DiscussionRenal cell carcinoma with leiomyomatous stroma Renal cell carcinoma accounts for approximately 3% of all cancer cases in adults, and 90% to 95% of kidney neoplasms. It is also more common in males than in females (2:1), and rare in children. Clear cell renal cell carcinomas accounts for 65% to 75% of all malignant renal tumors. Renal cell carcinoma with leiomyomatous stroma is a rare entity that is thought to be distinct from clear cell renal carcinoma, although research is ongoing. So far, no gender predominance has been found; the right kidney is affected as commonly as left. Renal cell carcinomas with leiomyomatous stroma are well-circumscribed tumors. The cut surface is typically gray-white fibrotic tissues composed of small nests and nodules of renal epithelial cells with clear cytoplasms. Carcinoma cells are embedded in a cellular stroma comprising intertwining bundles of smooth muscle. The leiomyomatous stromal component is proposed to be polyclonal and therefore reactive, rather than neoplastic. It is hypothesized to be derived from smooth muscle cells of large-caliber veins located at the peripheral capsular region or within the collagenous septae of the tumors. IHC is typically positive for CK7 and CD10, as well as CAIX, pankeratin, vimentin, and HIF1-alpha. The prognosis is generally good, with a low rate of tumor recurrence. Differential diagnostic methods for renal clear cell carcinoma include FISH, gene sequencing, and methylation-specific multiplex ligation-dependent probe amplification analysis; renal clear cell carcinoma will show deletion of chromosome 3p, VHL mutation, and VHL methylation abnormalities. Additional differential diagnostic methods may include genetic testing, as renal cell carcinomas with leiomyomatous stroma show recurrent mutations of TSC1/TSC2, MTOR, and/or ELOC, consistent with hyperactive MTOR complex. References
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