Diagnostic challenges and clinical management of inflammatory myofibroblastic tumor: a retrospective case series study.

Background: Inflammatory myofibroblastic tumor (IMT) is a relatively rare mesenchymal tumor in clinical practice and is difficult to diagnose. At present, clinical reports on this disease are still relatively scattered. Especially for IMT occurring in special sites such as the nasal cavity, sacrum, and bladder, systematic reports on its clinical manifestations, treatment responses, and prognostic characteristics are still lacking. Case Description: This study retrospectively reported six patients with low-grade IMT diagnosed by pathology (three males and three females), aged 15 to 63 years (with an average age of 41.67 years). The maximum diameter of the tumors ranged from 2.0 to 9.5 cm (with an average of 4.4 cm), and the involved sites included the nasal cavity, upper limbs, chest wall, sacrum, and bladder. All patients underwent surgical treatment and were followed up for 13 to 33 months after the operation (with an average of 19.67 months). Among them, one patient with nasal IMT had local recurrence after the operation, one patient with sacral IMT was found to have multiple bone metastases throughout the body during the follow-up period, and no recurrence or metastasis was observed in the remaining four cases. Conclusions: IMT is a tumor with "low malignant potential" or "borderline" characteristics. It is neither a typical benign tumor nor a highly malignant cancer, but occupies an intermediate gray zone. It can occur at multiple sites in the body, most commonly in the lungs, and has been reported across all age groups. Through the analysis of six cases of IMT with unusual primary sites, this study found that even with low-grade pathological features, the tumor can still exhibit aggressive biological behavior, including postoperative recurrence and distant metastasis, when arising in atypical locations such as the sacrum or nasal cavity. This suggests that the clinical management of IMT should not rely solely on pathological grading but should also involve a comprehensive evaluation incorporating the tumor's location and size. This case series contributes to broadening the understanding of the clinical spectrum of IMT, enhances awareness of IMT in rare sites, and provides important clinical rationale for long-term systematic follow-up and monitoring for all patients with IMT.