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Meningioma-like inflammatory myofibroblastic tumor of the lung with TPM3::ALK fusion
Ali Eren Akın1, Ceren Damla Durmaz2, Ayşe Nur Yılmaz3
1Department of Pathology, Hacettepe University School of Medicine, Sihhiye, Ankara, Türkiye.
Abstract:
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.
Insights
This study details a rare lung inflammatory myofibroblastic tumor (IMT) in a female patient. It highlights a unique meningothelial-like pattern and the TPM3::ALK fusion, offering insights into IMT diagnosis.
Area of Science:
- Oncology
- Pathology
- Genetics
Background:
- Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal neoplasm.
- IMTs typically exhibit spindle cells, inflammation, and ALK/ROS1 rearrangements.
- Lung IMTs present diagnostic challenges.
Purpose of the Study:
- To report a unique case of lung IMT.
- To describe its distinct meningothelial-like pattern.
- To investigate its genetic profile and diagnostic implications.
Main Methods:
- Histopathological examination of lung tumor tissue.
- Immunohistochemistry for ALK expression (clones 5A4 and ALK1).
- Fluorescence in situ hybridization (FISH) for ALK rearrangement.
- Molecular analysis to identify gene fusions (TPM3::ALK).
Main Results:
- The lung IMT displayed a meningothelial-like whorl pattern.
- Equivocal ALK expression was observed (5A4 negative, ALK1 positive).
- FISH confirmed no ALK rearrangement, but TPM3::ALK fusion was detected.
Conclusions:
- This case represents the first reported lung IMT with meningothelial-like whorls.
- The TPM3::ALK fusion in the absence of typical ALK rearrangement is noteworthy.
- Accurate diagnosis requires comprehensive molecular and histological evaluation.
