Primary Corneal Squamous Cell Carcinoma Confined to the Cornea: An Unusual Presentation of Ocular Surface Squamous Neoplasia Without Limbal Involvement

Ocular surface squamous neoplasia manifests primarily on the limbus, with occasional extension onto the cornea. Primary corneal squamous cell carcinoma (SCC) devoid of limbal involvement is an exceptionally rare occurrence. The present case report details a 58-year-old male painter who experienced progressive blurred vision for three months and was diagnosed with SCC strictly confined to the corneal epithelium in his right eye, with no extension to the limbus. Clinical examination revealed significantly reduced visual acuity (0.2 or 20/100 with correction) and diffuse corneal epithelial opacity without limbal or conjunctival involvement, which was initially unresponsive to topical steroid treatment. The patient had no significant medical history. His occupational exposure to painting materials may constitute a potential risk factor. The unique manifestation of SCC, limited to the cornea, posed a significant diagnostic challenge by deviating from the conventional limbal-originating pattern. The patient underwent a biopsy, followed by a complete surgical excision with intraoperative application of 0.04% mitomycin C (MMC), supplemented by postoperative topical 5-fluorouracil (5-FU) therapy. This case underscores the necessity of considering SCC in the differential diagnosis of persistent corneal epithelial lesions, even when the limbus appears uninvolved, and demonstrates an effective treatment approach for this rare entity.