ABSTRACT
Well differentiated thymic carcinoma(WDTC) was recently separated from cortical thymoma. It is characterized by a predominance of epithelial cells with usually low mitotic rate, an epidermoid differentiation with slight to moderate cytologic atypia and lobular growth pattern. In recent reports, an uncommon spindle cell variant of WDTC, which is composed of spindle shaped epithelial cells, has been described. We investigated an unusual case of WDTC consisted of purely spindle shaped epithelial cells in a 66-year-old female. Radiologically, the well demarcated mass was located in the anterior mediastinum with focal invasion into the surrounding left upper lung. The tumor, 10 x 8 x 5 cm, was encapsulated with thin fibrous tissue and showed a pale yellow solid and lobulated cut surface. Microscopically, it consisted of solid sheets of purely spindle shaped epithelial cells with mild atypism, a low mitotic rate and focal epidennoid differentiation.