Fig. 2

Gross appearance (a) and histological findings (b-f) of the lung of the index patient. a Gross analysis of the lung resection specimen shows an inhomogeneous consolidation of the parenchyma (beige). b, c Microscopic findings denote a dense lymphocytic infiltrate consisting of monomorphic small lymphocytes (H&E). d Double staining for PAX5 (brown) and a pan-cytokeratin (AE1/AE3, red) demonstrate lymphoepithelial lesions. e Numerous intra- and perilesional epithelioid cell granulomas with multinucleated giant cells are similarly observed in adjacent parenchyma (f) (H&E). b Scale bar: 500 µm. c–f Scale bars: 50 µm