Mixoid leiomyoma of the vagina: case report with emphasis to diagnostic challenges.

Leiomyoma is the most common benign mesenchymal tumour of the vagina in adult women,1 but no case of myxoid variant has been reported at this site. A 27-year-old nulliparous woman was admitted to hospital for dyspareunia, pressure symptoms on the urinary tract, vaginal pain and prolonged vaginal discharge. By vaginal exploration, a soft mass was palpated in the anterior wall vaginal measuring 7 × 6 cm. The magnetic resonance images revealed a vaginal tumour arising from the anterior vaginal wall (Fig. 1a,b). Enucleation of the vaginal tumour using a transvaginal approach was performed. The mass was a well-encapsulated solid tumour measuring 8.5 × 7.5 × 6.5 cm with a smooth, pink surface. The cut surface was yellow and soft with a whorled or slightly nodular pattern and focal grey gelatinous areas. On microscopic examination, the majority of the tumour was hypocellular with delicate spindle cells dispersed in an amorphous, pale blue matrix (Fig. 1c). The matrix was positive for Alcian blue and colloidal iron stainings and was faintly positive for mucicarmine staining. Focal areas resembling typical leiomyoma were present. Nuclear atypia was absent, and the highest mitotic count was 1MF/10 HPF. The tumour cells showed strong positivity for muscle specific actin and focally for desmin. Fourteen months after the surgical removal, she was asymptomatic. Vaginal leiomyomas vary in size up to 5 cm, and sometimes may simulate malignancies (large size, unusual subtype, degenerative changes). Microscopically vaginal leiomyomas resemble those of the genital tract organs and may display bizarre,2 epithelioid and clear cell patterns.3 Since the first report by Denys de Leyden in 1773, approximately 300 cases have been reported.4 The criteria used for smooth-muscle tumours of the uterine corpus appear to be organ-specific and cannot be applied to counterpart arising elsewhere in the female genital tract. In evaluating vaginal smooth muscle tumours, we apply the criteria of malignancy used by Tavassoli and Norris3: presence of moderate to marked atypia and five or more mitotic figures per 10 high-power fields. Myxoid change may be seen in both benign and malignant smooth muscle tumours. This change has achieved notoriety in the uterus because some myxoid leiomyosarcomas have little nuclear atypia and a low mitotic rate making evaluation of borders crucial for placement in either a benign or a malignant category. In our case the tumour was well circumscribed, with no cytological atypia and a low mitotic rate. The diagnosis of benignancy is confirmed by follow up. After 14 months of surgical removal, the patient is free of disease. In the diagnosis of myxoid leiomyoma another diagnostic challenge is found when the myxoid degeneration is extensive. In this instance it may be difficult to identify the smooth nature of the tumour. A desmin or actins staining may be helpful in this situation. In our case the positivity of actin was diffusely found, although extensive mixoid areas were present. After a review of the literature, we shall consider that this is the probably first case report of myxoid leiomyoma of the vagina.