Pulmonary Langerhans cell histiocytosis presenting as a solitary nodule

Solitary pulmonary nodules are an uncommon manifestation of pulmonary Langerhans cell histiocytosis (PLCH). We describe a 45-year-old male cigarette smoker who presented with an asymptomatic solitary pulmonary nodule that showed histologic and immunophenotypic characteristics of PLCH. Twenty-one years after excision of the nodule, at the age of 66 years, he is asymptomatic with a new contralateral lung nodule but no evidence of interstitial disease. The new nodule has remained unchanged after 36 months of observation. This case affirms that PLCH can occasionally cause solitary lesions, which should not be interpreted as a harbinger of interstitial lung disease. Isolated PLCH should be included in the differential diagnosis of unusual solitary pulmonary nodules.