PULMONARY PUZZLE
Answer
Transthoracic needle aspiration of the mass showed abundant small mature lymphocytes and some atypical cells with cytological abnormalities. An immunoperoxidase panel revealed a positive reaction with pankeratin, vimentin and LCA stains. Stains for MOC-31, Ber-EP4, TTF-1 and calretinin were negative. The pathologist at the local hospital suggested a possible large cell carcinoma of a lymphoepithelioma type but requested further investigation.
A CT-guided core biopsy stained for cytokeratin 5/6 and p63, supporting the diagnosis of a pleural-based thymoma. There was a separate infiltrate consistent with lymphocytic interstitial pneumonitis (LIP). This …
