Primary squamous cell carcinoma of the breast presenting as a breast abscess.

Primary squamous cell carcinoma (SCC) of the breast is a very rare neoplasm, with only 75 cases reported in the English literature. Herein, we report four new cases and discuss the diagnostic and therapeutic challenges of this unusual tumor in a retrospective review of all cases of SCC of the breast at our institution from 1990 to 1998. Four patients with breast SCC were identified, with a mean age of 70 years. Two patients with "pure" SCC (no features of ductal carcinoma) were initially treated for breast abscess. Two other patients with features of both SCC and ductal carcinoma had skin erythema associated with an underlying mass, and infectious etiology was considered in each case. Mean tumor size was 4.9 cm. Both patients with pure SCC underwent extensive evaluation for primary tumors at other sites. Two patients developed early systemic metastasis. SCC of the breast is often diagnosed at an advanced stage and may be confused with breast abscess. For this reason, breast biopsy should be considered in cases of breast abscess. Treatment of primary SCC of the breast is similar to that of more common types of breast cancer (i.e., breast conservation is possible and lymph node dissection is recommended). Because metastasis to the breast from other primary tumor sites has been reported (lung, cervix, skin, and esophagus), patients with pure SCC should undergo evaluation to exclude this possibility.