[Orbital and eyelid inflammatory myofibroblastic tumors: a clinicopathological analysis of 13 cases].

<b>Objective:</b> To investigate the clinicopathological features of orbital and eyelid inflammatory myofibroblastic tumors (IMTs). <b>Methods:</b> A retrospective analysis was conducted among 13 patients with IMTs treated at Tianjin Eye Hospital between January 2000 and October 2023. The clinicopathological data, immunohistochemical staining characteristics, molecular phenotypes, and follow-up outcomes were collected and analyzed. <b>Results:</b> The study cohort comprised 7 males and 6 females. The median age was 44 (22, 68) years. The tumor was observed in the left eye in 6 cases and the right eye in 7 cases. The age at onset ranged from 5 to 76 years, with a disease course of 1 month to 2 years before tumor excision. The tumor was located within the orbit in 10 cases (including one case of a systemic multifocal lesion) and in the eyelid in 3 cases. Pathological characteristics of the tumors were mainly proliferation of spindle or ovoid fibroblasts and myofibroblasts, with varying degrees of mucoid degeneration or collagenization of the mesenchyme, and varying amounts of lymphocytes and plasma cells infiltrated in the background. Immunohistochemical analysis revealed that Vimentin and α-SMA were positive in all cases (13/13, 13/13), ALK1 was positive in 5 cases (5/11), CK was positive in 1 case (1/1), and Desmin was positive in 1 case (1/6). ALK fluorescence in situ hybridization was positive in 2 out of 3 cases, and EBER in situ hybridization was negative in 6 cases. Nine patients were available for the follow-up of 7 to 139 months. Seven patients remained tumor-free, 2 experienced relapses, and no deaths or metastases were reported. <b>Conclusions:</b> Orbital and eyelid IMTs predominantly occurred in adults, with localized lesions in most cases and favorable prognoses. The disease was histopathologically characterized by proliferation of fibroblasts and myofibroblasts. The accurate diagnosis depended on a comprehensive assessment of the morphological features of the tumor histopathology as well as immunohistochemical markers such as ALK and α-SMA, and molecular detection.