Pulmonary anthracosis mimicking lung metastases in pediatric rhabdomyosarcoma

Although childhood rhabdomyosarcoma typically metastasizes to lungs, various processes may mimic metastatic etiology. Described herein is the case of an 8½-year-old boy with orbital embryonal rhabdomyosarcoma (RME) in whom three small foci were detected within both lungs on computed tomography. The lesion number and size, however, did not fulfil the Cooperative Weichteilsarkom Study Group 2006 protocol criteria for lung metastasis. Chemotherapy for localized RME produced primary tumor regression and vanishing of the left lung lesion. Two lesions in the right lung remained unchanged. On thoracoscopy multiple minute nodules disseminated in both lungs were detected. Histopathology excluded RME spread but indicated anthracosis in the lung parenchyma and intrapulmonary lymph nodes. Heavy smoking by parents and previous home furnace combustion appeared to be predisposing factors. Uncommon non-malignant intrapulmonary diseases, including anthracosis, should be considered when staging pediatric cancer.