Rapidly progressive malignant glomus tumor of the breast: a case report and review of the literature.

The glomus tumor is a rare neoplasm that is typically found subungually in the extremities and functions as a specialized neurovascular organ. An extremely rare site for glomus tumors is the breast, with only a few reported cases. Breast glomus tumors present with three typical clinical signs: dull pain, focal tenderness, and cold sensitivity. Less than 10% of all glomus tumors are malignant. We herein present a case of a malignant glomus tumor originating in the breast. Distant metastasis was ruled out, and the tumor was completely resected. However, the patient unexpectedly developed rapid systemic metastasis, detected 5 weeks after tumor removal. Despite the administration of analgesics and targeted therapy, the patient died 1 month later. When treating patients with undiagnosed breast tumors, clinicians should pay attention to unexplained and repeatedly reported symptoms and consider the possibility of a rare disease. Our literature search revealed no cases of malignant glomus tumors originating in the breast, making this case the first of its kind.