Aggressive, Widely Metastatic Inflammatory Myofibroblastic Tumor in an Adult Presenting as an Obstructing...

Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal neoplasm, most commonly occurring in children and young adults. It is typically locally aggressive and rarely metastasizes. Adult-onset IMTs with extensive metastasis are exceedingly uncommon, particularly with large pulmonary involvement, and can mimic sarcoma or sarcomatoid carcinoma on imaging and histology. Anaplastic lymphoma kinase (ALK) positivity aids diagnosis and provides a potential therapeutic target. A 56-year-old male presented with progressively worsening dyspnea, nonproductive cough, and right-sided chest pain. Computed tomography revealed a 9-cm right hilar and upper lobe mass causing complete obstruction of the right upper lobe bronchus, with extensive mediastinal lymphadenopathy. Bronchoscopic biopsy demonstrated a malignant spindle cell neoplasm with sarcomatoid and myxoid features. Immunohistochemistry was positive for ALK-1, CD68, and vimentin, and negative for epithelial, smooth muscle, neural, and melanocytic markers (AE1/3, p40, TTF-1, CK7, CK20, CDX2, SMA, desmin, SOX10, S100, and calretinin). Staging imaging revealed a mesenteric mass adjacent to the ascending colon. Biopsy of the colonic lesion showed morphologically and immunohistochemically similar features, supporting a diagnosis of metastatic IMT confirmed by multidisciplinary pathology review. The patient's clinical course was rapidly progressive, and he died two months after initial presentation. Adult-onset ALK-positive IMT with extensive pulmonary involvement and multiorgan metastases is exceedingly rare. This case highlights the diagnostic challenges posed by sarcomatoid morphology and underscores the importance of integrating histopathology, immunohistochemistry, and clinical correlation, with ALK testing providing both diagnostic confirmation and a potential therapeutic target.