Giant cellular blue nevus of the anterior chest wall mimicking metastatic melanoma to the breast: a case report.

Overview

BACKGROUND AND OBJECTIVES: Blue nevi are benign pigmented dermal lesions that can mimic cutaneous melanoma in appearance. Cellular components may infiltrate subcutaneous tissue. We present a complex case of cellular blue nevus (CBN) to demonstrate the ambiguous clinical appearance of these lesions and to provide an approach for management of such cases. METHODS: We report an extraordinary case of CBN mimicking metastatic melanoma to the breast. A 53-year-old female with an acquired giant blue nevus of the chest wall was found to have two new breast nodules suspicious for malignancy on routine mammography. These were biopsied and interpreted as consistent with metastatic melanoma vs. CBN. The patient underwent complete excision of the chest wall nevus and modified radical mastectomy. RESULTS: Pathologic evaluation of the chest wall specimen revealed numerous collections of deeply pigmented melanocytes scattered throughout the breast parenchyma and embracing ductal structures. No mitoses or nuclear polymorphism were seen. The diagnosis of CBN involving the chest, breast tissue and axillary lymph nodes was made. CONCLUSION: Giant blue nevi overlying the breast can develop cellular components that infiltrate subcutaneous and breast tissue resulting in the appearance of breast nodules on mammography. A generous excision biopsy inclusive of the overlying nevus and breast component may be required to establish the dignity of the lesion.