Benign metastasising leiomyoma: a rare disease and a diagnostic challenge

Benign metastasising leiomyoma (BML) is a rare tumour characterised by extrauterine metastasis of histologically benign leiomyomas. We present a case of BML with pulmonary involvement. A 49-year-old woman presented with large pelviabdominal masses complicated by gross abdominal and lower limb swelling 6 years following open myomectomy. Preoperative CT imaging showed pelviabdominal masses and multiple bilateral pulmonary nodules. Initial impression was that of a stage 4 gynaecological malignancy. Palliative total hysterectomy bilateral salpingo-oophorectomy was performed. Histopathology confirmed benign uterine leiomyomas. Biopsy of pulmonary nodules showed benign leiomyomas, strongly positive for oestrogen and progesterone receptors. Definitive diagnosis of BML was made on histopathology and immunohistochemistry. The patient declined letrozole treatment as she had just undergone bilateral oophorectomy. She opted for conservative monitoring of her lung nodules. CT imaging 7 months postsurgery showed disease regression. She will require long-term surveillance scans to detect disease progression.