Benign metastasizing pulmonary leiomyoma, a rare cause in the differentialdiagnosis of a space-occupying lesion of the lung

History and admission findings: A 45-year-old woman was reffered fbr diagno sis of an accidentally found symptomless space-occupying lesions in the cen tral part of the right lung. She had undergone a hysterectomy 4 years befor e and reported smoking 15 cigarettes daily since the age of 17 years. Physi cal examination was normal. Investigations: As primary bronchial carcinoma or metastasis to the lung wa s suspected she underwent a series of diagnostic tests: sonography, compute d tomography (CT), gastroscopy, coloscopy, bronchoscopy, skeletal scintigra phy, gynaecological examination and various laboratory tests, none of which indicated a primary extrapulmonary tumour. CT-guided fine-needle biopsy th en suggested benign metastasizing pulmonary leiomyoma (BMPL). Treatment and course: The largest of the tumours were surgically removed, c onfirming BMPL. Hormone receptors (for oestrogen, progesterone) having been demonstrated, progesterone treatment was initiated as prophylaxis against recurrences. CT 6 months later revealed new intrapulmonary foci. Administra tion of luteinizing hormone-releasing hormone analog to stop completely any oestrogen effect, and CT of the thorax 6 months later showed that both tum our numbers and their size had been reduced. The patient remained asymptoma tic and the findings had not changed in the subsequent 12 months. Conclusion: BMPL is a rare cause of a space-occupying pulmonary lesion, pre dominantly affecting middle-aged women after hysterectomy for uterine myoma . The pathogenesis remains unclear, hormone-dependent tumour growth being d iscussed as a possible mechanism. Anti-oestrogen administration is the trea tment of choice to achieve remission and effective prevention of recurrence s.