- Rare - estimated to represent 0.3% of treated renal tumours.
- Fasicular architecture.
- Spindle cells without significant atypia.
- Angiomyolipoma - typically contain adipose tissue.
- Leiomyosarcoma - typically have at least some of the following: nuclear atypia, mitosis, necrosis.
- HMB-45 -ve.
- Desmin +ve.
- ER and PR +ve (6 of 9 cases:).
Mass Lesion, Right Kidney, Core Biopsy: - Benign leiomyoma with hyalinization and without atypia, see comment. - Renal parenchyma within normal limits present. - NEGATIVE for malignancy. Comment: The tumour stains as follows: POSITIVE: desmin, SMA, ER, PR. NEGATIVE: HMB-45. Proliferation (Ki-67): 0%. The tumour histology and immunoprofile is that of a leiomyoma. Renal leiomyomas are very rare lesions; a large contemporary series has only 9 cases.  Correlation with radiology is suggested. 1. Am J Surg Pathol. 2015 Mar;39(3):349-56.
The sections show tumour with a fascicular architecture and hyalinization. No adipose tissue is seen. Necrosis is not identified. Nuclear atypia is not seen. Mitotic activity is not readily apparent. Benign unremarkable renal parenchyma is present.
- Khetrapal, S.; Bhargava, A.; Jetley, S.; Rana, S.; Jairajpuri, Z. (Oct 2014). "Renal leiomyoma: an uncommon differential diagnosis of renal masses with a clinical relevance.". J Clin Diagn Res 8 (10): FD08-9. doi:10.7860/JCDR/2014/9434.4993. PMID 25478354.
- Fu, L.; Humphrey, PA.; Adeniran, AJ. (Dec 2014). "Renal Leiomyoma.". J Urol. doi:10.1016/j.juro.2014.12.083. PMID 25526990.
- Patil, PA.; McKenney, JK.; Trpkov, K.; Hes, O.; Montironi, R.; Scarpelli, M.; Nesi, G.; Aron, M. et al. (Dec 2014). "Renal Leiomyoma: A Contemporary Multi-institution Study of an Infrequent and Frequently Misclassified Neoplasm.". Am J Surg Pathol. doi:10.1097/PAS.0000000000000354. PMID 25517956.