Microglandular adenosis (MGA) of the breast is a rare, benign proliferative lesion but with a significant rate of associated carcinoma. Herein, we report an unusual case of metaplastic carcinoma with chondroid differentiation associated with typical MGA. Histologically, MGA showed a direct transition to metaplastic carcinoma without an intervening atypical MGA or ductal carcinoma in situ component. The immunohistochemical profile of the metaplastic carcinoma was mostly similar to that of MGA. In both areas, all the epithelial cells were positive for S-100 protein, but negative for estrogen receptor, progesterone receptor, HER2/neu, and epidermal growth factor receptor. An increase in the Ki-67 and p53 labelling index was observed from MGA to invasive carcinoma. To the best of our knowledge, this is the first case of metaplastic carcinoma with chondroid differentiation arising in MGA in Korea. This case supports the hypothesis that a subset of MGA may be a non-obligate morphologic precursor of breast carcinoma, especially the triple-negative subtype.
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BACKGROUND Columnar cell lesions (CCLs) are characterized by the presence of columnar epithelial cells lining the terminal duct lobular units of the breast and frequently found in biopsies for microcalcifications. Their incidence and relationship with other lesions and the locations of microcalcifications have not been established. METHODS: We reviewed 1,038 cases of fibrocystic change (FCC) for the degrees of CCLs and ductal proliferative change (PC) and the locations of microcalcifications. RESULTS: Among 1,038 FCC cases, CCLs were found in 18.9%, columnar cell change (CCC) in 12.5%, columnar cell hyperplasia (CCH) in 5.3% and flat epithelial atypia (FEA) in 1.1%. CCLs were found in 14.2%, 28.8%, and 40.0% of non-PC (NPC), proliferative disease (PD) without atypia and PD with atypia, respectively.
Microcalcifications were found in 33.5%, 56.2%, 61.8%, and 81.8% of caese without CCLs, with CCC, CCH and FEA, respectively. Their locations were in NPC in 66.3% of the cases, PD in 14.8% of the cases or both areas in 18.8% of FCC. CONCLUSIONS: The incidence of CCLs increased according to the degree of PD without positive correlation between the degree of CCLs and PD. The frequency of microcalcifications increased according to the degree of CCLs but was statistically insignificant. There is a possibility that a needle biopsy targeting a microcalcification area might leave additional PD around the targeted area because microcalcifications were found more frequently in NPC than PD area.