Primary squamous cell carcinoma of the breast is a rare cancer. Published reports of prognosis are variable, and most studies are case reports of one or a few patients. We report an additional case of squamous cell carcinoma of the breast occurring in a 53-year-old black woman. In reviewing the reported cases of this tumor over the past 20 years, we compared features of this cancer with those of the more common breast adenocarcinoma with squamous metaplasia. When squamous cell carcinoma of the breast is encountered, a skin primary lesion and metastasis from a distant site should be excluded. Prognosis is determined largely by stage and does not differ significantly from the prognosis in breast adenocarcinoma with squamous metaplasia.