Pulmonary Langerhans' cell histiocytosis presenting as a solitary pulmonary nodule.

Abstract

Introduction: Pulmonary Langerhans Cell Histiocytosis (PLCH) is a rare disease of unknown etiology characterized by tissue infiltration with special dendritic cells. PLCH occurs almost exclusively in either current or former smokers. Patient usually present with dyspnea or cough and sometime with recurrent spontaneous pneumothorax. Computer tomography (CT) findings include upper zone predominant ill-defined nodules, cysts and reticulo-nodular infiltrates. Case report: A 53 years old female with known chronic obstructive pulmonary disease and a 35 pack years smoking history presented to her local emergency department with cough, purulent sputum and shortness of breath of 1 week duration. She had weight loss of 8lbs over the preceding 2 months. She denied fever, hoarseness of voice or hemoptysis. Her chest x-ray showed a nodule in the left upper lobe. She was treated with antibiotic and scheduled for an out-patient CT chest. The CT chest showed a 9 mm solitary lung nodule in the left upper lobe. There was no interstitial or cystic changes. Pulmonary function test demonstrated obstructive defect with moderately reduced diffusion capacity. There was concern for lung cancer given her smoking history and weigh loss. Videoscopic thoracic surgery and resection of the left upper lobe nodule were performed. The frozen section showed eosinophilic granuloma. Special stains on permanent histological sections were positive for CD1a and S-100 and a diagnosis of PLCH was made. Positron emission tomography (PET) scan showed no abnormal uptake. Patient had stopped smoking since being diagnosed with PLCH. She has been followed up for 2 years with repeat CT scans of chest that showed no further lung nodule or interstitial changes. Discussion: Langerhans cells are dendritic cells located beneath the epithelium of the tracheo-bronchial tree. Smoking activates these cells and it results in nodular and cystic formation in the lungs and in later stages causes fibrosis. PLCH presenting as an isolated lung nodule will be a diagnostic challenge. The surface of the Langerhans cell expressess CD1a which are detectable by an immunohistochemical stain in histological sections. In our case biopsy of the lung nodule and stains were positive for CD1a and S-100 which is consistent with a diagnosis of PLCH. The PET scan was negative and there was no other evidence of systemic involvement. The prognosis of PLCH is variable. A search in Pub Med shows only a handful of case reports of PLCH presenting as a solitary lung nodule. (Figure presented) .