MUCINOUS LESIONS OF THE BREAST - A PATHOLOGICAL CONTINUUM

Mucocele-like tumor and invasive mucinous carcinoma of the breast may represent the two ends of the pathological spectrum of mucinous lesion s of the breast, respectively. Little data exists on mucinous lesions that may be considered intermediate between mucocele-like tumor and in vasive mucinous carcinoma. We studied 23 consecutive cases of invasive mucinous carcinoma of the breast and observed the following associate d intermediate mucinous lesions: mucin-filled ducts (MFD) with unremar kable epithelium in 13 cases (65%), MFD with typical ductal hyperplasi a in 9 cases (39%), MFD with atypical ductal hyperplasia in S cases (2 2%), and MFD with intraductal carcinoma in 13 cases (57%; micropapilla ry or cribriform types). Eighteen cases (78%) contained MFD with one o f these four lesions and five cases (22%) contained all four lesions. Twenty-three consecutive cases of infiltrating ductal carcinoma-not ot herwise specified (IDC-NOS), 21 cases of intraductal carcinoma, and SO consecutive cases of surgically-excised breast tissue with fibrocysti c change (FC), were similarly reviewed. Only one case (4%) of IDC-NOS, 1 case of intraductal carcinoma, and two cases (4%) of FC, contained small foci of MFD with intraductal carcinoma, intraductal carcinoma, a nd unremarkable epithelium, respectively. Our findings suggest the pre sence of a spectrum of mucinous lesions of the breast which represents a pathological continuum.