Purpose: Metastatic melanoma to the extraocular muscles is an extremely rare condition characterized by marked enlargement of the involved muscles. The authors describe the echographic characteristics of metastatic melanoma to extraocular muscles.
Methods: The authors used standardized echography (standardized A-scan and contact B-scan) to examine two patients known to have malignant melanoma elsewhere with metastatic melanoma to the extraocular muscles. Both patients had orbital lesions with similar echographic characteristics.
Results: Echographically, metastatic melanoma to an extraocular muscle spares the tendon and produces marked thickening of the muscle belly fibers. Other echographic findings include low internal reflectivity, regular internal structure, and vascularity (similar to uveal melanoma). These previously unreported echographic features may be unique to metastatic melanoma to an extraocular muscle.
Conclusion: Echography can be a useful adjunct in detecting and diagnosing suspected metastatic melanoma to the extraocular muscles in patients with clinical signs of an orbital mass and known melanoma elsewhere or in the absence of a known primary lesion.