Ocular oncocytomas are rare neoplasms found mostly in the caruncle, conjunctiva, lacrimal gland and lacrimal sac. Clinically they are often mistaken for hemangiomas, nevi and cysts. Though rare, this tumour should be recognised by the ophthalmologists especially in the elderly, because of exceptional development of adenocarcinoma.
A 75-year-old woman was seen by us with a small growth at the inner corner of the right eye for the last 3 years. There was no history of trauma or eye surgery. The mass was reported to have grown slowly, and there was no history of bleeding or change in colour. She was a known diabetic on oral hypoglycemic agents for the past 10 years. On examination, her best-corrected visual acuity was 6/9 N10 in both eyes due to bilateral lenticular opacities. Slitlamp examination revealed a red broad-based and sessile growth on the caruncle in the right eye measuring 4 mm x 8 mm [Figure:1]. There was surface keratinisation with yellow dots. There was no surface ulceration. The nasolacrimal duct was patent in both eyes. A differential diagnosis of granuloma or cyst of the caruncle was considered. The caruncular mass was excised under local anaesthesia.
The mass measured 9 mm x 4 mm x 3 mm. Histopathologic examination showed conjunctival epithelium with multiple goblet cells. In the subconjunctival stroma cystic glandular structures with a papillary pattern were seen [Figure:2]. These comprised columnar cells with a low nuclear cytoplasmic ratio, round and paracentral nuclei, and an inconspicuous nucleoli. Mitotic figures were not seen. On higher magnification, the cells had an abundant finely granular eosinophilic cytoplasm (oxyphilic) Occasional goblet cells were intermixed with the oncocytes. The cystic spaces contained seromucinous material [Figure:3]. The underlying stroma was loose and contained few blood vessels and chronic inflammatory cells comprising lymphocytes and plasma cells. The cytoplasm stained positive with Periodic acid Schiff stain. A histopathologic diagnosis of cystic oncocytoma (oxyphilic adenoma) of the caruncle was made.
Oncocytoma of the caruncle has not been reported earlier in the Indian literature (Medline search) though it is not a rarity in the Western literature. Oncocytomas are tumours composed of transformed glandular epithelial cells called oncocytes that have abundant eosinophilic cytoplasm. Electron microscopy of the oncocytoma shows the cytoplasm packed with mitochondria of varying sizes and shapes with irregular and fragmented cristae and a fewer number of other organelles. Oncocytomas develop in glandular tissues throughout the body including the thyroid, parathyroid, pancreas and the liver. Oncocytomas occasionally develop from the accessory lacrimal gland tissue in the caruncle and they account for approximately 3-8% of biopsied caruncular masses. Radnot was the first to report oncocytoma of the caruncle, and subsequently several cases of oncocytomas of the caruncle have been reported. The caruncular oncocytoma appears clinically as a small (2-5 mm) slowly growing solid or cystic red tan mass. Biggs and Font have reviewed the clinicopathologic findings in 18 ocular oncocytomas on file at the Armed Forces Institute of Pathology. They reported that the tumour was more common among elderly females.
The caruncular oncocytoma is usually asymptomatic and is removed for diagnostic and cosmetic reasons, as in our case. Microscopically, the benign oncocytes appear as uniform, oval cells with abundant eosinophilic cytoplasm that accounts for the tumour’s alternative name of oxyphilic adenoma. The nuclei are small, round and have a single nucleolus. Occasionally goblet cells are scattered within the epithelial lining of the cystic tumour. There are three histopathological groups. In the first group, the tumour is composed of tubules lined by tall columnar epithelium with finely granular cytoplasm. The tubule often has dilated lumina containing mucous secretion. In the second group, the tumours are cystic and have prominent tufts projecting from the cyst wall. In the third group the tumours have solid areas composed of cuboidal or polygonal cells largely trabecular in arrangement and they coexist with previously described tubular and cystic elements.
Our case indicates that oncocytoma should be considered in the differential diagnosis of a caruncular mass in elderly people. The tumour is benign and no further treatment is needed if it is completely excised.
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