Rosen's Breast Pathology, 4e

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Chapter 33

to be encountered when ectopic breast tissue enlarges during pregnancy or in rare instances of fibroepithelial neoplasms arising from such tissue. 216 One unusual case in which the diagnosis was made by FNA involved a 45-year-old woman with a 3.0-cm subcutaneous lesion on the submammary FIG. 33.27.  Residual breast tissue with carcinoma after mastectomy. A: The patient underwent a mastectomy for intraductal carcinoma with clear cell features shown here. B: Nine years later a chest wall mass contained IDC with osteoclast-like cells ( arrows ). C: Benign breast tissue was also present.

(Fig. 33.29). In addition to carcinoma arising in ectopic breast tissue, the differential diagnosis of a FNA specimen containing atypical epithelial cells obtained from an axil­ lary mass includes a proliferative lesion in ectopic breast and metastatic carcinoma. Proliferative epithelium is most likely

FIG. 33.28.  Breast tissue in a mediastinal teratoma. A: A duct and atrophic lobular glands in fat. B: Magnified view of (A) .