Oncocytoma
Definition: Oncocytomas are benign tumors that arise most commonly in the caruncle or canthal conjunctiva but may also occur in the lacrimal glands (including accessory glands) and lacrimal sac.
Incidence/Prevalence: Oncocytomas are considered rare tumors.
Etiology: Oncocytoma are believed to arise from oncocytic metaplasia of ductal and acinar cells of lacrimal epithelium or perhaps conjunctival epithelium.
Clinical Findings: Oncocytomas most commonly present in women of middle age or older (>50 years) as a red-yellow mass (arrow 1 in the clinical photograph).
![](http://www.missionforvisionusa.org/anatomy/uploaded_images/wOncoClin-773467.jpg)
In this case the mass is red to pink in color, located in the caruncle and has a cystic appearance. Note the yellow lesion, a pingueculum near the limbus (arrow 2).
Histopathology: Oncocytomas are characterized by large eosinophilic cells that form glandular or ductular spaces (number 1 in the low mag photomicrograph).
Between the ducts there are solid trabeculae of cells.
![](http://www.missionforvisionusa.org/anatomy/uploaded_images/wlowmgonco-775671.jpg)
The abundant eosinophilic cytoplasm and the relatively small round to oval nuclei that are located in the middle of the epithelial cell (arrow 2) are key features.
![](http://www.missionforvisionusa.org/anatomy/uploaded_images/wOncocytohi-753354.jpg)
The cells may contain small nucleolar organizer regions (nucleoli) and their may be clearing of the nuclear material in some cells. Electron microscopy shows numerous mitochondria.
Treatment: Excision is usually curative.
Prognosis: It is believed by some that malignant transformation may occur to produce oncocytic adenocarcinoma, although this mode of transition has not been proven.