The Eye Never Lies: When A Lesion Unveils Lung Cancer.

Ocular manifestations rarely represent the first sign of systemic malignancy and often pose a diagnostic challenge. While choroidal metastases are more common, iris involvement is uncommon and may be underrecognized. Lung adenocarcinoma, particularly non-small cell subtypes, is a known source of ocular metastases, with iris lesions occasionally preceding systemic symptoms. We report a 70-year-old previously healthy man presenting with one month of left eye blurred vision. Initial examination revealed conjunctival injection and visual acuity of 6/20 without detectable lesions; topical dexamethasone was prescribed. Six weeks later, vision declined to finger counting, and a hypopigmented iris mass (7.0 × 5.7 mm) was identified. A brain MRI revealed a right occipital lesion, and a CECT of the thorax, abdomen, and pelvis showed a left lung mass with bilateral nodules, mediastinal lymphadenopathy, and right iliac metastasis. CT-guided biopsy confirmed stage IV lung adenocarcinoma (TTF-1 and Napsin A positive, PD-L1 TPS 80%, EGFR/ALK/ROS1 negative). Pembrolizumab was initiated; filamentous keratitis developed during therapy, and progression at three months prompted conventional chemotherapy. This case emphasizes the rarity of iris metastasis as the initial presentation of lung adenocarcinoma.