Melanocytoma, initially described in 1962, denotes a benign tumor typically situated within the optic nerve head[3]. However, rare occurrences have been documented originating from various ocular structures including the iris, ciliary body, choroid, sclera, and conjunctiva [3]. Iris lesions commonly present as flat, well-defined growths localized to the chamber angle and usually remain stable over time. In contrast, occasional cases display diffuse tumor growth with irregular surfaces and pigment dispersion, posing a significant risk for secondary glaucoma, as observed in our patient[4].
Distinguishing melanocytoma from melanoma remains a challenge. While melanocytoma can resemble iris nevus, rare cases show benign lesions can develop into melanoma[5, 6]. Manifestations in our case including irregular tumor surface, heavily pigment dispersion, and secondary glaucoma were considered as the possible indicators of melanoma[6].
Ultrasonography such as A-scan, shows inconsistent findings regarding melanocytoma characterization [3, 7]. Although a prior investigation highlighted the potential of high-resolution B-scan in conjunction with A-scan in the identification and monitoring of patients with melanocytoma, ultrasound remains incapable of distinguishing between melanocytoma and melanoma[8]. In our case, we suspected that the failure of ocular ultrasonography to detect the lesion could be attributed to subtle morphological changes involving the iris and ciliary body. On the other hand, UBM emerges as a preferable approach for evaluating such lesions, providing crucial details regarding growth patterns, tumor thickness, angle adhesion, and ciliary body involvement[9]. In our case, UBM clearly showed the irregular surface and thickening of the lesion of iris and the adjacent ciliary body with medium to high reflectivity, indicating ciliary body involvement. Since melanocytomas of the iris and ciliary body exhibit a variety of internal reflectivity patterns, as demonstrated by both our case and previous cases[10, 11], we suggest that it remains challenging to determine the malignancy of the tumor solely based on its internal reflectivity on UBM.[12]
Ocular melanocytomas typically exhibit hyperintensity on T1-weighted and hypointensity on T2-weighted magnetic resonance imaging (MRI) scans, similar to melanoma[3, 13, 14].However, distinguishing between the two based on MRI findings alone is difficult[15]. It is worth mentioning that (123)I-IMP SPECT has emerged as a promising tool for diagnosing malignant uveal melanoma, providing an option of distinguishing melanoma from melanocytoma[16]. However, in our case, neither MRI nor (123) I-IMP SPECT imaging was performed.
Biopsy plays a crucial role in diagnosing iris and ciliary body tumors like melanocytoma, as it provides cells and tissues for cytologic and histopathologic examination. Methods range from excisional techniques (such as iridectomy and iridocyclectomy) to less invasive approaches like fine-needle aspiration biopsy (FNAB), vitrector-assisted biopsy, and Kelly punch-assisted biopsy.
FNAB, though widely used with rare reported complications[17–19], may provide limited diagnostic accuracy due to cell quantity. Despite Shields and associates reported FNAB is effective in diagnose iris tumor with high sensitivity in 1993[18] and 2006[19], they emphasize the success depends on the experience of surgeon and cytopathologist. In our case, cytological examination followed FNAB was inconclusive for excluding melanoma. This highlights the importance of obtaining adequate tumor tissues for diagnosis. Finger et al[9] proposed an aspiration-cutter-assisted biopsy through the iris root, which offers both cells and tissue fragments for diagnosis and may provide greater diagnostic insight compared to FNAB.
Management of melanocytoma typically involves observation, with surgical options including iridectomy, iridocyclectomy, or enucleation due to melanoma concerns.[5, 6] Considering the failure of FNAB to rule out melanoma, and the necessity to treat glaucoma,[5, 6] a sector iridocyclectomy was performed for both diagnostic and therapeutic purposes. Histopathological analysis of the excised tissue revealed the presence of two distinct types of melanocytoma cells, with a predominance of type 1 cells over type 2 cells, and no mitotic activity was observed. Consistent with previous literature, small spindle cells were predominantly localized at the periphery of the tumor[20]. The histopathological evaluation definitively confirmed the diagnosis as melanocytoma.
In contrast to precedent cases [5], our patient exhibited transiently elevated IOP within the first postoperative month, which was effectively managed with a single antiglaucoma eye drop. Subsequently, IOP normalization occurred within 8 months without further medication. The identified risk factors for glaucoma in this condition included tumor invasion into the chamber angle and pigment dispersion[21]. Notably, residual pigment keratic precipitates were discerned in the surgical site at the 2-year follow-up, suggesting that the primary mechanism of glaucoma in this instance may be attributable to tumor-induced trabecular outflow obstruction and consequent angle closure.
In this case, the eyeball was saved from enucleation and resulting in satisfied BCVA and IOP, thus culminating in a successful clinical outcome. Reflecting on this diagnostic and therapeutic journey, we underscore the importance of tumor biopsy, we advocate for excisional procedures in patients presenting with secondary glaucoma, as these interventions not only afford adequate tissue for accurate diagnosis but also address chamber angle obstructions, thereby facilitating IOP reduction.