Bizarre leiomyoma of the prostate.

Obstruction of the urethra, caused by a prostatic tumour necessitated prostatectomy in a 49-yr-old man. Histology revealed a moderately cellular and vascular tumour with marked cellular atypia. After a follow-up for three years, the results of both the clinical investigations and prostatic needle biopsy were negative. Thus the original opinion of malignant prostatic mesenchymal tumour was revised, resulting in the diagnosis of bizarre leiomyoma. Subsequently the smooth muscle cell origin and the benign nature of the tumour were demonstrated by electron microscopy and Feulgen-cytophotometry, respectively. This is the first prostatic bizarre leiomyoma in which malignancy was excluded by demonstrating euploid polyploidy. This case also calls the attention to the need of more sophisticated methods in everyday diagnostic pathology.