Human Epidermal Growth Factor Receptor 2-Subtype Invasive Ductal Carcinoma Recurring as Basal-Human Epidermal Growth Factor Receptor 2-Subtype Squamous Cell Carcinoma.

Squamous cell carcinoma of the breast and its subtype, basal-human epidermal growth factor receptor 2 (HER2) phenotype, are very rare. Herein, we report a patient who developed recurrence of squamous cell carcinoma of the breast with basal-HER2 subtype 6 years after the initial diagnosis of invasive ductal carcinoma of the HER2 subtype. To the best of our knowledge, recurrence of invasive ductal carcinoma in the form of metaplastic squamous cell carcinoma of basal-HER2 subtype has not been reported previously. We present a pathological perspective of our experience.