High-grade spindle cell metaplastic carcinoma of the breast in a 15-year-old girl.

Metaplastic breast cancer in pediatric patients is exceedingly rare with only occasional case reports to present imaging and guide management. Typically diagnosed in patients over 50 years old, metaplastic carcinoma is an aggressive type of breast cancer representing less than 1% of all breast cancers in the United States. To our knowledge, we describe the youngest person to be diagnosed with metaplastic breast cancer in the US. This case underscores the need for clinical vigilance in evaluating rapidly growing breast masses in adolescents. It also emphasizes the value of histopathologic confirmation, even when imaging findings suggest a benign process, to ensure timely diagnosis and management.