Prostate carcinoma metastasis to extraocular muscles

Prostate carcinoma, when metastatic, typically involves bone and produces both osteoblastic and osteolytic changes. Orbital involvement is uncommon and extraocular muscle enlargement is a rare presentation of metastatic prostate adenocarcinoma. The authors present 2 patients with prostatic tumor metastasis to extraocular muscles. One patient had single-muscle involvement; the other presented with bilateral progressive proptosis, upper eyelid retraction, and bilateral multiple extraocular muscle enlargement mimicking thyroid-associated orbitopathy. Clinicians should be aware that, although rare, prostate cancer can involve the extraocular muscles.