OBJECTIVETo investigate the pathology, diagnosis and differential diagnosis of carcinomas arising in fibroepithelial neoplasms of the breast.

METHODSMorphological observation and immunohistochemistry using MaxVision method were performed in fifty-four cases of carcinoma arising from fibroepithelial neoplasms of the breast from January 2003 to February 2014.

RESULTSThirty-eight cases of carcinoma arose from fibroadenomas. Twelve cases were classical lobular carcinoma in situ (LCIS). Twenty-one cases were ductal carcinoma in situ (DCIS), including four cases of low-grade, ten cases of intermediate-grade, six cases of high-grade and one case of apocrine. One case was mixed DCIS and LCIS. Three cases were infiltrating ductal carcinoma (IDC) accompanied with DCIS. One case was spindle cell metaplastic carcinoma. Sixteen cases arose from phyllodes tumours. Six cases arose from benign phyllodes tumours, including four cases of low-grade DCIS, one case of high-grade DCIS, and one case of classical LCIS with micro-invasion (diameter 0.9 mm). Three cases arose from borderline phyllodes tumours, including one case of classical LCIS, one case of intermediate-grade DCIS, and one case of invasive lobular carcinoma (ILC) with LCIS. Seven cases arose from malignant phyllodes tumours, including two cases each of low-grade DCIS and intermediate-grade DCIS, one case of high-grade DCIS, one case of apocrine DCIS, and one case of mixed IDC with DCIS. By immunohistochemistry, LCIS and ILC were diffusely positive for ER and PR. Low-grade DCIS was diffusely positive for ER and PR ( > 90%), intermediate-grade DCIS was 70%-90% positive, high-grade DCIS was negative for ER and 20%-30% positive for PR, apocrine DCIS was both negative, and IDC was 40%-90% positive. The spindle cell metaplastic carcinoma was negative for ER and PR, but showed diffuse or scattered positivity for CK5/6 and p63.

CONCLUSIONSCarcinomas arising from fibroepithelial neoplasms of the breast are rare, showing unusual clinical presentation, and are characterized by in situ or invasive carcinomas in a background of fibroepithelial neoplasms. The accurate diagnosis depends on the recognition of the background fibroepithelial neoplasms and assessment of the nature of the epithelial proliferation, supplemented by immunohistochemistry when necessary.