A rare case of heterologous breast leiomyosarcoma in a pregnant female: challenges in diagnosis and management

Abstract

Primary breast sarcomas are exceptionally rare malignancies, accounting for less than 1% of all breast neoplasms and fewer than 5% of all soft tissue sarcomas. Primary leiomyosarcoma (LMS) of the breast is a rarer subtype, comprising less than 0.0006% of all breast malignancies. Fewer than 90 cases have been documented in the global literature since the disease was first described. The occurrence of a malignant phyllodes tumour harbouring heterologous leiomyosarcoma during pregnancy represents a rare case presentation. We present the case of a 37-year-old G2P1L1A0 women with gestation period of 24 weeks presented with a left breast lump of one year duration of size 10x8 cm that was painless and without any concerning features. Patient did not have any comorbidities or a significant family history. Ultrasonography was suggestive of a benign lactational adenoma. Core biopsy revealed borderline phyllodes tumour. Simple Mastectomy was done in second trimester with the final histopathological diagnosis of malignant phyllodes with heterologous component of leiomyosarcoma. Although breast leiomyosarcomas are rare and carry a more favourable prognosis than other primary non-phyllodes breast sarcomas, the presence of a malignant phyllodes tumour with heterologous LMS component the patient at a substantial risk for local recurrence or delayed hematogenous metastasis. Given that recurrence and metastasis can arise even after prolonged latent periods of 15 to 20 years, rigorous, lifelong clinical and radiological follow-up remains mandatory.