A Case Report of Anaplastic Lymphoma Kinase-Negative Inflammatory Myofibroblastic Tumor in the Anterior Mediastinum of an Elderly Male.

Inflammatory myofibroblastic tumor (IMT) is an uncommon mesenchymal neoplasm of intermediate biological potential, characterized by proliferating myofibroblastic spindle cells with a prominent inflammatory infiltrate. Although IMT occurs more commonly in children and young adults, primary involvement of the anterior mediastinum is exceedingly rare, particularly in older male patients, and may mimic more common anterior mediastinal tumors such as thymoma or thymic carcinoma. The authors report on a 68-year-old male patient with an incidentally detected anterior mediastinal mass. Contrast-enhanced chest computed tomography and magnetic resonance imaging revealed a 6.6 × 3.6-cm anterior mediastinal soft-tissue lesion with heterogeneous enhancement, peripheral delayed enhancement, central hypoenhancement, restricted diffusion, and an indistinct interface with adjacent pericardial structures. The patient underwent complete surgical resection via median sternotomy. Histopathological examination showed spindle-cell proliferation with a prominent lymphoplasmacytic infiltrate, supporting the diagnosis of IMT. Immunohistochemistry showed anaplastic lymphoma kinase (ALK) negativity. Additional ancillary studies showed negative staining for CD21, CD23, and CXCL13 and negative Epstein-Barr virus (EBV)-encoded small RNA in situ hybridization, arguing against follicular dendritic cell sarcoma and EBV-associated lesions. Fluorescence in situ hybridization showed no rearrangements involving ALK, ROS1, RET, or PDGFRB. The patient recovered well without adjuvant therapy, postoperative CA125 and neuron-specific enolase levels returned to the normal range, and no recurrence or metastasis was observed during 2 years of follow-up. This rare case highlights that ALK-negative anterior mediastinal IMT should be considered in the differential diagnosis of anterior mediastinal masses across age groups. Complete resection may provide durable disease control in selected resectable cases, but the single-case nature of this report and the known recurrence potential of IMT support cautious interpretation and long-term surveillance.