Primary ductal adenocarcinoma of the lacrimal gland with changing genetic analysis mutations

Primary ductal adenocarcinoma of the lacrimal gland is a rare but highly aggressive epithelial malignancy with a poor prognosis. Early diagnosis, along with genetic testing of these tumors, is imperative for proper management. We present a case of a 54-year-old man with decreasing vision over the past three years and increasing proptosis in his right eye over the past three months, secondary to a lacrimal gland mass diagnosed as primary ductal adenocarcinoma. The diagnosis was made using histological and immunohistochemical profiles (positivity for cytokeratin AE1/3, CAM5.2, androgen receptor, human epidermal growth factor receptor 2, and gross cystic disease fluid protein 15) seen in previous cases, alongside a tumor genetic profile that showed actionable mutations. Uniquely in this case, after failing traditional chemotherapy, repeat biopsy revealed a change in genetics with the malignancy no longer showing actionable mutations. These findings show that these immunohistochemical findings can act as diagnostic biomarkers, while genetic testing can reveal actionable mutations for targeted therapy.