Papers of the Week

BACKGROUND Langerhans cell histiocytosis (LCH) is a rare condition caused by a neoplastic proliferation of myeloid cells. It can present as a single-system or multi-system disorder. Worse prognosis is associated with the hematopoietic system (spleen, liver, bone marrow), which is routinely observed in multi-system disease. Because of the varied presentation of this disorder, diagnosis can be difficult, and therefore suitable treatment can be delayed. CASE REPORT We report a case of hepatic LCH in a 51-year-old man who presented with epigastric abdominal pain, with imaging demonstrating a hepatic nodule. A low ejection fraction on hepatobiliary iminodiacetic acid scan suggested chronic cholecystitis. Therefore, the patient underwent a cholecystectomy for biliary dyskinesia, in which liver nodules were noted, and biopsies were taken. The biopsies demonstrated characteristic findings of LCH along with positive immunohistochemical markers and negative BRAF V600E mutation. Radiologic and pathologic findings were consistent with LCH within the liver, associated with bile duct injury and mild biliary obstruction. The patient was placed on a cladribine regimen. His abdominal pain improved. CONCLUSIONS LCH limited to the liver is uncommon and can appear as chronic biliary disease, as was suspected in this case. Despite the poor prognosis of hematopoietic LCH, early recognition can lead to better outcome and chemotherapy susceptibility. This patient was most likely in the first stage of liver LCH, given his presentation, which could have aided his response to chemotherapy. The lack of BRAF V600E mutation could have contributed to a positive prognosis and more possibilities for treatment.