Review of extraocular muscle biopsies and utility of biopsy in extraocular muscle enlargement.

AIMS: To review the distribution of pathology in extraocular muscle (EOM) biopsies performed at a tertiary orbital centre, identify clinical and imaging features which are associated with benign or malignant diseases and indicate when biopsy is necessary for EOM enlargement.

METHODS: Retrospective case series including 93 patients with EOM enlargement who underwent an EOM biopsy. Clinical, radiological and histopathological information was recorded from the medical records. Statistical analysis was used to compare variables between patients with malignant and benign biopsies.

RESULTS: The median age of subjects was 61.1 years. Forty-eight cases (52%) were benign and 45 (48%) were malignant. Those with malignant pathology were significantly older (P<0.0001). Males were more likely affected by a benign disease and females by a malignancy (P=0.029). A history of malignancy (P<0.0001) and diplopia (P=0.029) were significant factors in predicting a malignancy. Pain (P=0.005) and eyelid erythema (P=0.001) were more likely in benign conditions. Idiopathic orbital inflammation was the most common benign diagnosis and lymphoma the most common malignancy.

CONCLUSIONS: Biopsy is warranted in those with an atypical presentation of EOM enlargement or suspected of having a malignancy. Some features such as age, gender, pain, diplopia, history of malignancy and eyelid erythema may help indicate a particular diagnosis; however, clinical features and imaging findings are often not pathognomonic of each disease.