Conventional leiomyomas may originate from any anatomic location of smooth muscle in the genitourinary system[1
]. Isolated cases of leiomyomas have been reported arising from the renal pelvis, bladder, spermatic cord, epididymis, prostate as well as the glans penis [1
]. However mesenchymal lesions of the scrotum are rare lesions[5
]. Leiomyomas are well known to be by far the commonest neoplasm arising from the uterus[6
Symplastic leiomyomas are rarely reported lesions in the medical literature [7
] A medline search reveals less than 10 reports of symplastic or "bizarre" leiomyoma of the scrotum.
On gross sections these tumours appear white-grey and are well circumscribed and encapsulated. On high power images these neoplasms are characterised by interlacing bundles of spindle shaped muscle cells with pleomorphic nuclei and occasional nuclear inclusions (Figure ). The muscular nature of these lesions can be demonstrated by positivity for Masson-trichrome staining[5
]. There are no mitotic figures seen (Figure ). Immunohistochemically, the tumour cells express vimentin, desmin, smooth muscle actin, and muscle specific actin, but not cytokeratin, neurofilament, or glial fibrillary acidic protein[11
A histopathological slide demonstrating the characteristic interlacing bundles of spindle shaped muscle cells with pleomorphic nuclei and occasional nuclear inclusions found in symplastic leiomyomas.
It is important to emphasize that despite their histological characteristics on presentation, compatible with malignancy, these tumours have a benign course not any different from conventional leiomyomas even when they are larger in size than those reported in the literature. In contrast to scrotal leiomyosarcomas, scrotal leiomyomas with bizarre nuclei are not hypercellular, and they lack mitotic activity[11
Ultrasound scan appears to be the investigation of choice in the pre-operative assessment of these tumours [7
] and should ensure a proper surgical approach with simple excision of the tumour.