Answer: Sclerosing non-mucinous bronchioalveolar carcinoma with involvement by CLL/SLL

Histology: none provided

Discussion: The sections of lung show an adenocarcinoma that exhibits a lepidic growth pattern with variable amount of sclerosis in the alveolar septae. No definite invasion is noted. In addition, along the alveolar septa there are monotonous lymphoid infiltrates that involve the lung parenchyma in a patchy distribution. The infiltrate is dense and is composed of small round cells with mature chromatin. Immunohistochemical stains show that the atypical lymphocytes are CD20-positive B-cells that co-express CD5, CD43 and variably express CD23. Cyclin D1 expression was not seen. Kappa and lambda stains were non-contributory. The findings are consistent with the flow cytometry phenotype reported in a prior peripheral blood specimen (in 2003) and now represent lung involvement by CLL/SLL.