Concurrent Breast Cancer and Vulvar Leiomyoma in a 62-Year-Old Patient: A Comprehensive Case Report

The detection of incidental masses in cancer patients, such as vulvar leiomyomas, is rare and can complicate the diagnostic process. We report a case of a 62-year-old woman who presented with a large, neglected breast tumor, which raised clinical suspicion of metastatic breast cancer. A computed tomography scan showed an osteosclerotic pelvic lesion, raising concern for bone metastasis. A whole-body positron emission tomography scan revealed no bone metastasis but detected a hypermetabolic left vulvar mass, presumed to be a Bartholin cyst. Surgical excision confirmed it to be a vulvar leiomyoma. The patient underwent neoadjuvant chemotherapy for breast cancer, followed by a left radical mastectomy with significant residual tumor burden. Currently, the patient is receiving radiotherapy along with adjuvant hormonal treatment, and CDK4/6 inhibitor therapy is scheduled after the radiotherapy. When found incidentally during cancer staging, vulvar leiomyomas can cause diagnostic confusion. This case highlights the importance of a comprehensive and multidisciplinary differential diagnostic approach in the oncological assessment of cancer patients to avoid misdiagnosis and guide appropriate treatment strategies.