Anterior Uveal Melanocytoma: Role of Diagnostic FNAB

Abstract

Purpose: Anterior uveal melanocytomas (AUM) pose a diagnostic challenge as they can mimic growing melanomas. Establishing a definitive diagnosis of melanocytoma necessitates cytologic or histopathologic confirmation. We describe the clinical presentation and characteristics of fifteen pathologically proven AUM and assess the role of fine needle aspiration biopsy (FNAB) as a safe and effective tool for diagnosis. Methods: Retrospective review of pathologically confirmed AUM cases of iris and/or ciliary body was performed. Demographic data, presenting symptoms, clinical features, diagnostic approach, cytological and histological features, and clinical outcomes were collected. Results: Fifteen patients with pathologically confirmed AUM were identified. Mean and median age of diagnosis were 50 and 53 years, respectively (range 3-77 years). The melanocytoma was localized to the iris (5, 33%), ciliary body (7, 47%), while 3 patients had iridociliary involvement (20%). Four (29%) patients presented because of concern for growth, 10 (64%) were noted incidentally, and visual symptoms were noted in only 1 case (7%). Pigmentation of the tumor varied with 9 tumors (60%) appearing brown and 3 (20%) black tumor. The color of 3 (20%) ciliary body tumors could not be assessed. The diagnosis was confirmed with FNAB in 6 cases (40%), excisional biopsy in 7 cases (47%), and incisional biopsy in 2 cases (13%). Cytologic and histologic preparations both demonstrated predominance of round to polygonal cells with heavily pigmented cytoplasm, and small round nuclei. One patient who underwent excisional biopsy had prior FNAB that was interpreted as suspicious for melanoma (false positive). Instances of false negative cytology were not observed as demonstrated by subsequent stable clinical course during mean follow-up of 21.2 months (range=1-63 months). FNAB related complications were not observed in any case. Conclusion: FNAB offers a minimally invasive and safe diagnostic approach for pathologic confirmation of AUM. However, limitations of FNAB including false-negative and false-positive biopsies must be considered when excluding underlying malignancy. Continued observation to document tumor stability should be considered.