Infarction and squamous metaplasia of intraductal papilloma: a benign breast lesion that may simulate carcinoma.

Infarction of intraductal papillomas is uncommon. Six lesions of this type was referred to the authors as diagnostic problems, and two additional cases were found in a review of in-patient material. The patients' median age was 62 years (range, 30 to 81 years), and in each case the mass had been asymptomatic. Although the architectural pattern of the papillomas remained intact, ischemic necrosis rendered histologic evaluation difficult. Squamous metaplastic epithelium was present in three cases. Distortion of residual viable ductal epithelium by fibrosis at the periphery of the papillomas closely simulated invasive carcinoma. The appearance of the lesion on low-power magnification, the absence of malignancy elsewhere in the sample, and the absence of cytologic features of malignancy are useful criteria for distinguishing this lesion from carcinoma. None of these lesions recurred in the six patients for whom follow-up information was available (follow-up period, one to 20 years).