Pulmonary myoepithelial carcinoma resembling matrix-producing carcinoma of the breast: case report and review of the literature.

We report a case of pulmonary myoepithelial carcinoma with extensive myxohyaline stroma, resembling matrix-producing carcinoma of the breast. A 76-year-old Japanese man presented with a nodular lesion in the left lung (S8), and underwent partial resection of the left lower lobe. Microscopically, the resected tumor was relatively well circumscribed with central hypocellular myxohyaline and peripheral hypercellular area. In the central area, eosinophilic and clear polygonal cells proliferated in a cord-like or reticulated pattern with extensive myxohyaline stroma, while the peripheral area was composed of solid lobules of different shapes and sizes with occasional comedonecrosis. The tumor cells were markedly atypical with frequent mitotic figures. Vascular and lymphatic invasion was evident with regional lymph node metastasis. No squamous or glandular differentiation was evident in the tumor. Immunohistochemical staining implied myoepithelial differentiation. The patient developed multiple brain metastases, and died of the disease 11 months after the surgery. In this report, we discuss the histopathologic uniqueness of the present case together with a review of the literature.