Mucinous carcinoma of the skin: evaluation of lymphatic invasion with D2-40.

Primary cutaneous mucinous carcinoma is a rare adnexal sweat gland neoplasm that mainly affects elderly people. Differential diagnosis includes mammary and gastrointestinal metastatic mucinous carcinoma (MC) and secondary cutaneous involvement by underlying neoplasms. An 83-year-old woman presented with an 8-year history of slow-growing infiltrate plaque in her right hemithorax, with ulceration on supraclavicular area, right upper limb edema and palpable axillary lymphadenopathies. She underwent partial excision of the tumor and local radiotherapy. Imaging studies showed widespread cutaneous dissemination with enlargement of ipsilateral axillary lymph nodes but without evidence of underlying breast cancer. Histopathological examination showed large amounts of mucin in the dermis including small islands of epithelial cells. They stained positive for cytokeratin 7, carcinoembryonic antigen, epithelial membrane antigen, gross cystic disease fluid protein-15, and c-erbB-2. Lymphatic invasion was demonstrated by D2-40-immunostained sections. A diagnosis of primary cutaneous mucinous carcinoma was made. Our aim was to reevaluate the differential clinical, histopathological, and immunohistochemical criteria for distinguishing primary cutaneous mucinous carcinoma from skin metastases of visceral mucinous carcinoma, especially those arising in breast. We also propose D2-40 as a reliable marker to detect lymphatic invasion that indicates a strong aggressive trend with shorter recurrence-free and predicts nodal metastases.