The Fine Line Between Benign And Malignant: Differential Diagnosis Of Pigmented Anterior Segment Tumors

Anterior segment melanocytic neoplasms or tumors constitute a clinical spectrum ranging from benign lesions, such as melanocytoma, to malignant neoplasms, such as melanoma. Melanocytoma accounts for 0.5% to 3% of iris tumors, while ciliary body melanoma represents approximately 10% to 15% of uveal melanomas. Despite exhibiting similar clinical features, their evolution, prognosis, and therapeutic management differ substantially.

A comparison of clinical characteristics was conducted alongside complementary diagnostic studies, specifically ultrasonography and ultrasound biomicroscopy (UBM). Both cases were confirmed via histopathological analysis and diagnostic auxiliaries, including immunohistochemical reactions.

• Case 1: A 21-year-old female presented for consultation regarding an iris nevus. Biomicroscopy identified a pigmented, nodular lesion with well-defined borders, displaying corneal endothelial contact and pigment dispersion. Upon ruling out tumor extension to adjacent structures, a total resection via iridectomy was performed for histopathological analysis.
• Case 2: A 54-year-old male presented with a one-month history of decreased visual acuity in the right eye. Physical examination revealed a nodular lesion with irregular borders originating from the ciliary body, with invasion into the iris and endothelial contact. Given the suspicion of malignancy, systemic staging was performed to rule out distant metastasis, and a complete resection via iridocyclectomy was scheduled.

The melanocytoma presented as a pigmented nodular lesion with medium-to-high internal reflectivity on UBM and no evidence of invasion into the ciliary body or choroid. Conversely, the melanoma exhibited rapid progressive growth and sudden visual loss. UBM assessment showed medium-to-low reflectivity and invasion of adjacent structures.

Initial clinical assessment of these tumors provides significant diagnostic value. Correlation between clinical, imaging, and histopathological findings is essential for the differentiation of pigmented tumors. Diagnostic precision directly impacts both the visual and systemic prognosis of the patient.