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Abstract. Malignant granular cell tumors (MGCT) are rare mesenchymal soft tissue neoplasms of Schwann cell origin without adequate follow-up. This study describes a case of MGCT with right breast metastasis following two local recurrences. The patient consented to a right breast lumpectomy with right axillary dissection, a right abdominal wall lumpectomy and a right inguinal lumpectomy with dissection. Pathological examination revealed that the two initial lesions were consistent with benign histological performance. The later lesions were classified as malignant due to the observation of spindling of the tumor cells, vesicular nuclei with large nucleoli and increased mitotic rate. Immunohistochemical study of the lesions revealed positivity for S100 protein. The Ki-67 proliferation index increased from 1 to 10%. Twenty-seven months after surgery, the patient was in good health with no sign of further tumor development. We recommend wide local excision with regional lymph node dissection as the first choice of treatment for MGCT.

Autophagy and ferroptosis have been major foci of biomedical research in recent years. Elucidation of their intrinsic molecular relationships is important for cancer prevention and treatment. Metformin can directly inhibit tumorigenesis, although the mechanism responsible for this is not fully understood. Here, we demonstrate that metformin and lncRNA‐H19 can regulate both autophagy and ferroptosis. Autophagy inducers and H19 can reverse the production of lipid reactive oxygen species and the inhibition of autophagy induced by metformin. The present study suggests that metformin may induce ferroptosis by inhibiting autophagy via H19, and this discovery may facilitate the development of novel therapies for the treatment of breast cancer.