Gestational squamous cell carcinoma of the breast: an unusual mammary tumor associated with aggressive clinical course.

We report two cases of squamous carcinoma of the breast detected during the gestational period. One woman was post-partum and lactating; one was in the first trimester of pregnancy. The lesions were clinically palpable, multifocal, and measured more than 5 cm in their largest dimension; both had a cystic appearance. They were treated with radical mastectomy. One patient received pre-operatory chemotherapy. Histologically, the tumors were poorly differentiated squamous cell carcinomas. No areas of ordinary duct differentiation were seen. Lymph nodes contained metastatic squamous carcinoma in both cases. Tumor cells were negative for estrogen and progesterone receptors. Also, they expressed a high proliferative index and several markers of tumor progression, including cErb-B2, p53 protein, bcl-2, and epidermal growth factor receptor. One patient died of tumor 5 months following breast surgery and had extensive metastases proven at autopsy. The other patient had evidence of pulmonary metastases: following cisplatin therapy, she underwent clinical remission. This study shows that squamous carcinoma of the breast may occur in pregnant or lactating women: it appears clinically distinguishable from the non-gestational type that is usually associated with a better prognosis and occurs in peri- or postmenopausal women.