Adenomyoepithelioma of the breast masquerading as malignancy in a young female: report of a rare case

Adenomyoepithelioma (AME) of breast is a rare breast tumor accounting for less than 0.5% of all breast tumors. AME of the breast is an epithelial myoepithelial tumors, characterised by biphasic proliferation of both epithelial and myoepithelial cells. This tumor can exhibit both benign and malignant behaviour, often showing property of recurrence. We present a case of a young female of 35 years of age with palpable mass in left breast and skin ulceration. Radiographically, the lesion was categorised as BIRADS 5, which on fine needle aspiration showed clusters of ductal epithelial cells with overlying myoepithelial cells. Few clusters showed mild nuclear pleomorphism with nuclear overlapping, thus categorised as Yokohama category 3 (Atypia of undetermined significance) on FNAC. Thus based on probably benign nature of the lesion on FNAC, the patient underwent nipple sparing partial mastectomy. On microscopic examination, well circumscribed multilobulated areas with biphasic proliferation of epithelial and myoepithelial cells were seen. These cells were round to polygonal with clear cytoplasm and vesicular chromatin. No foci of malignant transformation were seen. Section from ulcerated area did not show any tumor infiltration in the dermis and there was no epidermotropism seen. On immunohistochemistry, CK7 showed diffuse strong cytoplasmic positivity in the ductal epithelial cells, while P63 showed nuclear positivity in the myoepithelial cells. Ki-67 was low (< 1%). Based on the histomorphological features and immunohistochemistry, a diagnosis of benign adenomyoepithelioma of the left breast was rendered. The patient was on regular follow up and she was absolutely fine after one year of follow up without any new complain. We report this case because of presentation in young age, skin ulceration which is unusual in benign cases and due to disparity in radiological and cytological findings.