Pulmonary langerhans cell histiocytosis diagnosed in a cervical lymph node: a case report.

Background Pulmonary Langerhans cell histiocytosis (PLCH) is usually confined to the lungs and is therefore an unexpected finding in a cervical lymph node. Case A 52-year-old male with a 40-pack-year smoking history presented to our clinic with cough, fever and cervical lymphadenopathy. Chest computed tomography (CT) showed bilateral pulmonary nodules and enlarged mediastinal lymph nodes, worrisome for an infectious or malignant process. Bronchioloalveolar lavage was nondiagnostic. Fine needle aspiration cytology of the enlarged cervical lymph node revealed atypical histiocytoid cells, suspicious for malignancy. Immunohistochemistry revealed CD1a- and S-100-positive Langerhans cells. These findings, along with the patient's extensive smoking history and characteristic radiographic nodules, favored a diagnosis of PLCH with cervical lymph node involvement. The patient was advised to cease smoking, and no therapy was administered. Months later, follow-up chest CT showed spontaneous resolution of the lung nodules. Conclusion The demonstration of Langerhans cells by immunohistochemical staining of CDla and S-100 on a fine needle aspiration cell block is a useful diagnostic adjunct. In this case, definitive cytology for Langerhans cells in the appropriate clinical and radiologic setting allowed us to arrive at the correct diagnosis of PLCH in a minimally invasive manner.