A Rare Case of Primary Adenocarcinoma of the Eyelid: Case Presentation and Review of Literature.

Primary mucinous adenocarcinoma (PMA) of the eyelid is a very rare malignancy with an incidence of 0.07 per million. Most cases are elderly males with an indolent course of local growth over months. We report a rare case of a 61-year-old gentleman with an aggressive course of PMA. The patient presented with a painless lower right eyelid swelling that developed over a four-month period. Incisional biopsy of the mass disclosed mucinous adenocarcinoma, positive for cytokeratin (CK)7 but negative for thyroid transcription factor 1, S100, and CK20 expression. Magnetic resonance imaging of the orbits revealed an enhancing infiltrative mass extending from the right lower eyelid to the medial canthus and posteriorly into the orbit, the right ethmoid sinuses, and extraconal fat within the orbit. Workup for metastatic disease including scans of chest, abdomen, and pelvis as well as positron emission tomography/computed tomography were negative for other masses. The patient underwent extensive surgery that included exenteration of the right orbit and cervical lymph node dissection followed by adjuvant radiation therapy and chemotherapy due to the extent of periorbital tumor invasion of contiguous tissues. Diagnosis of PMA is a clinical challenge, and immunohistochemistry is essential for diagnosis. To confirm it as a primary tumor, exclusion of metastasis from elsewhere is appropriate. Reported treatment modalities include Mohs micrographic surgery or excision with frozen section and safety margin. Exenteration of the orbit may be indicated depending on the extent of orbital invasion by the tumor. There is limited evidence to guide treatment and follow-up, with information consisting mostly of published case reports and case series.