Conjunctival stromal tumour (COST) is a rare benign tumour arising from mesenchymal cells.1 There is a wide array of clinical appearances. While the distribution of COST is either localized or diffuse, its color ranges from red to yellow to white, and its physical description can vary from a cystic lesion, to a nodule, to a fibrovascular infiltrate on the ocular surface. It grows slowly over many years. According to Herwig et al., the differential diagnosis of this lesion includes conjunctival (cellular) myxoma, neurothekeoma, subconjunctival herniated orbital fat, fat-free spindle cell lipoma, pseudotumour, neurofibroma, dendrocytoma, nevus with neuronal degeneration, solitary fibrous tumour, fibrous histiocytoma, nodular fasciitis, hemangiopericytoma, giant cell angiofibroma, and rhabdomyosarcoma.
A 68-year-old female was referred to the emergency ophthalmology clinic with a pigmented iris lesion and an intraocular pressure (IOP) of 38 in her left eye. Initial clinical assessment revealed the presence of a localized, flat, plaque-like peripheral and midperipheral iris lesion in one quadrant. Pigmented seeding on the rest of the iris surface and associated mild corectopia were observed. There were no notable episcleral sentinel vessels, and there was no iris neovascularization. On gonioscopy, heavy pigment invaded 8 clock hours of the angle (Fig.