Preliminary study of positron emission tomography in the detection and management of orbital malignancy

Purpose: To determine the clinical efficacy of positron emission tomography (PET) in the treatment of patients with orbital malignancy. Methods: Prospective, consecutive case series to assess the ability of PET to (1) identify lesions previously demonstrated on CT or MRI; (2) characterize the metabolic activity of these lesions; and (3) determine the presence of metabolically active metastases elsewhere in the body. Results: Eighteen patients with suspected orbital malignancies, ages 32 to 78 years, underwent PET in addition to CT and/or MRI. Sixteen of 18 also underwent orbital biopsy. Histopathologic diagnosis included lymphoma (55%), carcinoma (22%), melanoma (11%), sarcoma (5.5%), and lymphoid hyperplasia (5.5%). All orbital lesions were seen on conventional imaging. Overall, 61% of orbital lesions were demonstrated on PET, including 55% of tumors that were lymphoproliferative and 100% (n = 5) of other malignancies. PET was useful in ruling out tumor recurrence after exenteration in 2 patients. Conclusions: In this small clinical series, PET proved effective in demonstrating nonlymphoproliferative orbital malignancy. This series is too small to study any correlation between histopathologic aggressiveness and PET findings in orbital lymphoma.