Squamous cell carcinoma of the breast

To review the mammographic and ultrasonographic features of primary breast cancer containing squamous cell carcinoma.

From medical records for breast cancer patients seen over a 37-year period the authors identified 19 patients with squamous cell carcinoma, for 5 of whom histologic sections and imaging studies were available. The tumours were classified on the basis of histologic findings as pure (in two patients) or predominantly (in three patients) squamous cell carcinoma. Mammograms were available for four of the patients, and the mammographic report only was available for analysis for the fifth. Ultrasonography had been performed for four of the patients; the images were available for two of the patients and the reports only for two.

The median age of the patients was 55 years. The mean size of the tumours, all of which were palpable, was 5.0 cm. None of the tumours was connected to the skin, arose in the nipple-areolar complex or was metastatic. On mammography, the margins of all five masses, which were oval in shape, were indistinct and partly well-circumscribed; in three cases, the tumour margin was also partly spiculated. No malignant microcalcifications were seen. The two "pure" squamous cell carcinoma tumours appeared on ultrasonography as solid hypoechoic masses, and two of the predominantly squamous cell carcinoma tumours had both cystic and solid components. At gross pathological examination, four of the tumours (two "pure" and two predominantly squamous cell carcinoma) were cystic, which reflected areas of necrosis and cyst formation.

Although "pure" or predominantly squamous cell carcinoma is a rare histologic variant of breast cancer that lacks any typical mammographic features, this tumour can be added to the differential diagnosis of cystic breast masses seen on ultrasonography.