Malignant adenomyoepithelioma of the breast with metastasis in the thyroidgland 12 years after excision of the primary tumor - Case report and review of the literature

We describe a patient who was admitted to our hospital with an enlarged lef t lobe of the thyroid gland. Since fine-needle aspiration showed atypical f ollicular cells, a surgical exploration followed. Owing to extensive tumor infiltration into the surrounding tissues curative surgery was not possible , and only an incisional biopsy was taken. Histological examination of this biopsy revealed a mixed tumor composed of epithelial and myoepithelial cel ls. A primary thyroid tumor, metastasis of a salivary gland, and a skill ap pendage turner could be excluded based on clinical examination, conventiona l histology, and immunohistochemistry. A tumor of the left breast treated 1 2 years earlier had originally been classified as an intraductal/intracysti c carcinoma with focal invasion, but was re-examined. Using immunohistochem istry, the breast tumor was reclassified as a malignant adenomyoepithelioma . The current tumor was apparently a metastasis from this primary breast tu mor. An updated review of the literature is given, including current knowle dge on histological and immunohistochemical features of adenomyoepithelioma of the breast, with special attention to the reported pathological charact eristics of recurrent and malignant tumors. Based on the reported pathologi cal characteristics of recurrent and metastatic tumors we offer a diagnosti c tool for identifying potentially malignant and recurrent tumors.