A rare case of coexistence of pulmonary adenocarcinoma with Langerhans' cell histiocytosis.

We report a rare case of coexisting pulmonary adenocarcinoma and Langerhans' cell histiocytosis (LCH) in a 78-year-old woman who did not smoke. During follow-up of diabetes mellitus, she had complained of chest pain and was found to have a nodular lesion in S9 of the left lower lobe, which was resected surgically. No abnormal laboratory findings were obtained. Before surgical resection, needle biopsy specimens confirmed the existence of adenocarcinoma. The resected tumor in the left lower lobe was 3.0 x 1.8 x 3.0 cm, and histologically both acinar and bronchioloalveolar cell subtypes of adenocarcinoma were found in cancer foci. In addition to pulmonary adenocarcinoma, Langerhans' cell proliferation associated with marked eosinophil infiltration was incidentally found in a small nodule, approximately 3 x 2 mm in size in the subpleural region. The Langerhans' cells contained interdigitated nuclei, exhibiting rather clear nucleoplasm and cytoplasm; they were positive for S-100 protein, CD1a, and also CD4. Massive eosinophil infiltration was found around the focus of Langerhans' cell proliferation. This nodule appeared to be LCH. The adenocarcinoma and LCH were adjacent, and cancer cells were infiltrated only in the peripheral parts of LCH. The coexistence of adenocarcinoma and LCH appeared to be incidental. The association of adenocarcinoma and LCH is rare, and only several reports of it can be found in the English literature.