Poorly Differentiated Nonkeratinizing Squamous Cell Carcinoma of the Thymus: Clinicopathologic and Molecular Genetic Study of 25 Cases

Thymic carcinoma represents a rare and poorly understood type of thymic epithelial neoplasm that has been the subject of much controversy. Poorly differentiated nonkeratinizing squamous cell carcinoma, also known as lymphoepithelioma-like thymic carcinoma, is a rare variant of thymic carcinoma that has not been adequately characterized in the literature. The clinicopathologic, immunohistochemical, ultrastructural, and molecular features of 25 cases are reported. The patients were 19 men and 6 women, ranging in age from 20 to 85 years (mean: 60 y). The tumors presented clinically as anterior mediastinal masses with chest pain and shortness of breath or were found incidentally on imaging studies. Tumor size ranged from 2.0 to 13.5 cm in greatest diameter. Most of the tumors were small, well-circumscribed and confined to the mediastinum. Five cases presented with large, bulky, and infiltrative masses. Histologically, the hallmark of these tumors was a neoplastic proliferation of large, round to oval cells with vesicular nuclei, prominent eosinophilic nucleoli, and scant cytoplasm. Two histologic growth patterns were identified: tumors with a heavy lymphoplasmacytic stroma (lymphoepithelioma-like pattern), and tumors showing abundant desmoplastic stroma (desmoplastic pattern). Immunohistochemical stains showed strong positivity of the tumor cells for cytokeratin AE1/AE3, CK5/6, CK18, MOC31, p16, p40, and p63. MIB-1 showed on average 35% nuclear positivity. CD117 was positive ...
Source: The American Journal of Surgical Pathology - Category: Pathology Tags: Original Articles Source Type: research