Conjunctival metastatic adenocarcinoma of unknown origin.

We describe the case of a presumed metastatic adenocarcinoma discovered in the conjunctival limbus of a 75-year-old male with a history of prostate adenocarcinoma. After an initial clinical diagnosis of pinguecula and unsuccessful topical steroid therapy, the lesion was excised and sent for pathological evaluation and special staining. The histopathological evaluation was consistent with a diagnosis of adenocarcinoma, without evidence of lacrimal tissue. Surprisingly, results from special staining were most consistent with lung adenocarcinoma rather than that from a prostate origin. Systemic radiographic evaluation did not locate the primary tumour, and the patient did not present with any symptoms consistent with malignancy. Watchful waiting was chosen as the therapeutic strategy to manage the patient. This is the first report of an adenocarcinoma, likely metastatic, at the conjunctival limbus. 2016 BMJ Publishing Group Ltd.