Anaplastic lymphoma kinase-positive pulmonary inflammatory myofibroblastic tumor with sarcomatous morphology and distant metastases: An unusual histomorphology and behavior.

Inflammatory myofibroblastic tumor (IMT), an intermediate-grade neoplasm of myofibroblastic/fibroblastic differentiation, occurs commonly in children and young adults. It is characterized by anaplastic lymphoma kinase (ALK) gene rearrangement and overexpression of ALK-protein. However, aggressive behavior is more commonly associated with ALK-negativity rather than ALK-positivity. Pulmonary involvement is most common visceral location and carries minimal potential for distant metastasis. We present a case of 49-year-old female with pulmonary IMT of spindle cell sarcomatous histomorphology. Frequent mitoses and necrosis with characteristic cytoplasmic immunoreactivity for ALK-1 protein and ALK-gene rearrangement on fluorescence in-situ hybridization were noted. This case is unusual for occurrence in higher age-group of fifth decade, sarcomatous histomorphology at presentation (rather than transformation) and metastases to distant sites despite ALK-protein overexpression and gene rearrangement.