Cytohistological findings and diagnostic challenges in rare pediatric pulmonary mesenchymal malignancies: A report of two cases.

Pulmonary mesenchymal tumors are uncommon neoplasms and the data available on their clinical, cytohistomorphological, immunohistochemical, and molecular findings are limited, leading to difficulty in timely diagnosis and management. Case 1: A 12-year-old boy presented with a right endobronchial mass. Imprint smears from endobronchial biopsy revealed moderately pleomorphic spindle cell tumor arranged in fascicles and perivascular pattern with attached myxoid material showing occasional mitotic activity suggesting a cytological diagnosis of sarcoma. Biopsy also displayed similar morphology. Extensive immunohistochemistry (IHC) showed diffuse SMA, focal AE1/AE3, and diffuse ALK positivity along with a MIB/Ki67 index of 30%-40% leading to the diagnosis of inflammatory myofibroblastic tumor (IMT; Sarcoma grade). Case 2: A 8-year-old boy presented with a huge left-sided mass replacing the entire lung parenchyma and eroding adjoining ribs. Pleural fluid cytology revealed vague clusters of PAS-positive diastase-sensitive small atypical cells with associated inflammatory cells in the hemorrhagic background, suggesting a diagnosis of malignant small round blue cell tumor. Trucut biopsy from the mass showed spindled to round cells showing diffuse positivity with CD99 and BCL-2. Molecular studies with reverse transcription-PCR (RT-PCR) for SYT-SSX and EWS-FLI1 were negative for synovial sarcoma and Ewing's sarcoma, respectively. Given the clinical setting, PAS positivity, IHC, and molecular studies, the diagnosis of tumors of uncertain differentiation with the possibility of Ewing's sarcoma family of tumors (ESFT) with a translocation between EWS1 and other ETS-family members (ERG, FEV, ETV1, E1AF, etc.) was suggested.