Primary extraskeletal ewing’s sarcoma of the lung

Abstract

Ewing’s sarcoma/primitive neuroectodermal tumour (PNET) is a neuroectodermal tumour that characteristically arises from bone in the young population (5–20 years). Extraskeletal Ewing’s sarcoma (EES) is rare. We are aware of only 12 reported cases of primary lung EES. We report an additional primary pulmonary EES in a 38-year-old man who presented with cough, fever, right upper lobe consolidation in the chest X-ray and multiple RUL CT nodular masses. The clinical diagnosis was pneumonia. The mediastinal lymph node cytology showed cohesive atypical cells with minimal to absent cytoplasm and nuclear molding with smearing artifact. The lung core tissue fragments were diffusely replaced by malignant monotonous small round blue cells with some crash artifact, forming loose groups, clusters, islands and irregular sheets (positive for CD99 and vimentin positive; negative for TTF1, MNF, EMA, AE1/AE3, CK7, CK20, chromogranin, CD56, synaptophy-sin, calretinin, CD45, PLAP and S100). EWS rearrangement was positive. The PET scan showed a metabolically active malignancy in the RUL with ipsilateral hilar and mediastinal lymph node metastasis and a right parietal lesion suspicious for metastasis. No bone lesions were detected. Pulmonary EES is a rare aggressive malignant tumour that needs to be included in the differential diagnosis of pulmonary small round blue malignancies.