Benign metastasising leiomyoma with endometrial carcinoma, with a differential diagnosis of metastatic lung cancer.

Benign metastasising leiomyoma (BML) is a rare disease in which histologically benign uterine fibroids spread throughout the body. It is thought to originate from the hematogenous metastasis of myoma cells following myomectomy. To date, BML has been noted in patients with respiratory symptoms, even during regular checkups. There are few case reports of co-occurrence with gynaecological cancer. We report the case of a suspected stage IVb carcinoma based on preoperative examination for endometrial cancer, that indicated lung metastasis. However, postoperative pathology revealed a grade 1, pT1a pN0 tumour. We suspected BML based on the discrepant findings and history of myomectomy, and this was confirmed by lung biopsy. In metastatic lesions of a carcinoma patient with a history of myomectomy, the co-occurrence of BML should be considered when there is discrepancy between the preoperative suspected stage and postoperative pathology.