Meningioma-like inflammatory myofibroblastic tumor of the lung with TPM3::ALK fusion

Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal tumor characterized by spindle cells with myofibroblastic differentiation, accompanying chronic inflammatory cells, and the hallmark genetic signature of mainly ALK or ROS1 rearrangements. Here, we report a lung IMT in a 45-year-old female demonstrating a unique meningothelial-like pattern, equivocal ALK expression (negative for clone 5A4 and positive for clone ALK1), negative ALK rearrangement by FISH, and the presence of the TPM3::ALK fusion. To our knowledge, this is the first reported case of lung IMT displaying meningothelial-like whorls, with a particular focus on differential diagnosis.