Renal leiomyoma: gross pathology and histology
Incidental renal mass identified on CT abdomen
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Unfixed, bivalved right kidney specimen
Macroscopic - Circumscribed, pale, rubbery, 100mm in diameter, in the upper pole of the right kidney. The tumour has a 'whorled' cut surface, reminiscent of a uterine fibroid.
Microscopic - Intersecting fascicles of smooth muscle cells with relatively uniform, 'cigar' shaped nuclei, eosinophilic cytoplasm and indistinct cell boundaries. Malignant features including mitotic activity, pleomorphism and necrosis are not seen.
Leiomyoma is a benign tumour of smooth muscle. It is seen most commonly in the uterus (uterine 'fibroid'), gut and skin, but it is recognised to occur wherever smooth muscle is present.....which is virtually everywhere as smooth muscle is present in the walls of arterial and venous vessels.
Renal leiomyoma is an uncommon condition. Most present as small capsular/subcapsular tumours, with only rare lesions presenting as a clinically relevant mass. There is an even more uncommon malignant counterpart, renal leiomyosarcoma.
Despite the characteristic macroscopic appearance, the diagnosis of leiomyoma is determined histologically, with intersecting fascicles of smooth muscle cells often with interspersed blood vessels. The tumour cells have uniform, spindled nuclei and the tumour lacks significant mitotic activity or necrosis.
- Katabathina VS, Vikram R, Nagar AM et-al. Mesenchymal neoplasms of the kidney in adults: imaging spectrum with radiologic-pathologic correlation. Radiographics. 2010;30 (6): 1525-40. doi:10.1148/rg.306105517