ALK and neoplasm: Given that genetic testing revealed no evidence of tumor origin, differentiation pathway, or relevant genetic alterations – and considering the histological findings of mild-to-moderate atypia, readily identifiable mitotic figures, elevated proliferative index, and necrosis – pathologists currently favor a diagnosis of either an ALK-negative IMT or a rare low-grade malignant/indolent mesenchymal neoplasm with uncertain differentiation and intratumoral thrombosis.