Carcinoid Tumor Metastases to the Extraocular Muscles: MR Imaging and CT Findings and Review of the Literature

Although a relatively rare neoplasm, primary carcinoid tumor has or unusual propensity to metastasize to the orbits. Within the orbit, metastatic EOM lesions have been described in scattered reports in the ophthalmology literature but have received little to no attention in the radiology literature. After a retrospective review, we identified CT and MR imaging studies of 7 patients with carcinoid tumor metastatic to the EOM. Our findings suggest that in patients with known carcinoid tumor, well-defined, round, or fusiform masses of the EOM should strongly suggest metastatic involvement. Our series suggests that bilateral lesions may occur and that any EOM can be involved. Knowledge of this pattern of metastatic disease may spare biopsies in some patients, and with current orbit-sparing therapy for patients with localized orbital disease, early and accurate diagnosis can significantly improve patent outcomes.