Adenomyoepithelioma of the breast misdiagnosed as invasive ductal carcinoma

Sibel BEKTAŞ; Burak BAHADIR; Banu DOĞAN GÜN; Sacide ÇOLAK; Şükrü Oğuz ÖZDAMAR

The consultation material of total mastectomy and axillary lymph node dissection specimens taken from a 34-year-old female with a previous diagnosis of invasive ductal carcinoma was evaluated. Microscopic examination of the 6,5 cm well-circumscribed tumor revealed rounded tubules lined by both epithelial and myoepithelial cells in a myxomatous stroma. Obvious smooth muscle differentiation and area of fibroadenoma were also noted. Immunohistochemically, myoepithelial cells and cells with smooth muscle differentiation exhibited vimentin and smooth muscle actin. Myoepithelial cells were also reactive for S100 protein and epithelial membrane antigen. Luminal epithelial cells revealed positive reaction for epithelial membrane antigen and pan-cytokeratin (AE1/AE3), but displayed only focal staining with carcinoembryonic antigen. Based on these findings a final diagnosis of adenomyoepithelioma was made. Differential diagnosis of adenomyoepithelioma from its malignant counterpart and invasive ductal carcinoma may occasionally be challenging. Moreover, although considered an indolent neoplasm but with a potential risk for recurrence and sometimes metastasis, adenomyoepithelioma of the breast requires long-term followup.