Five cases of primary
thymic carcinoma with distinct histopathological features resembling chromophobe
carcinomas are presented. The patients were four men and one woman ranging in age between 43 and 72 years. Clinically, the patients presented with non-specific symptoms of
dyspnea and
chest pain. Diagnostic imaging revealed the presence of anterior mediastinal masses. All patients underwent complete surgical resection of their
tumors via
thoracotomy. Grossly, the
tumors measured between 4.0 and 5.5 cm in greatest diameter and were ill-defined
neoplasms with infiltrative borders; they were light brown in color and had a lobulated surface. Areas of
hemorrhage and
necrosis were not identified. Histologically, all
tumors shared similar histopathological features, mainly the presence of infiltrative
tumor islands separated by a fibrocollagenous stroma. At higher magnification, the neoplastic cellular proliferation was composed of medium-sized, round to polygonal cells with eosinophilic or granular cytoplasm and a clear perinuclear cytoplasmic halo, which imparted a chromophobe-like appearance. Nuclear atypia and mitotic activity were identified. Histochemical stains for colloidal
iron were negative while immunohistochemical stains for pancytokeratin,
cytokeratin 5/6, and p40 were positive in all cases, supporting squamous differentiation in these
tumors. Clinical follow-up information was obtained in three patients all of whom died between 3 and 5 years after initial diagnosis, while two patients were lost to follow-up. The cellular characteristics of these
tumors represent an unusual variant of
thymic carcinoma that may pose a diagnostic challenge in small biopsies and that could be easily confused with other primary or metastatic
tumors.