A case of masquerade syndrome caused by metastatic iris tumor diagnosed by a high CEA level in the aqueous humor and iris biopsy.

Background: With the advent of targeted therapies, the survival prognosis for metastatic tumors has extended, and it has become necessary to diagnose and consider treatment that takes into account Quality of Life for metastatic tumors of the eye. The reports of checking tumor marker in the aqueous humor for diagnosis of metastatic intraocular tumors are few. Here, we report a case of masquerade syndrome with secondary glaucoma in which a high carcinoembryonic antigen (CEA) level in the aqueous humor could assist diagnosis, and continuing targeted therapy and trabeculectomy were effective.

Case presentation: A 73-year-old man was referred to us for iritis and high intraocular pressure (IOP) with severe eye pain in the left eye. He had Stage IVB lung adenocarcinoma treated with a molecularly targeted drug, Osimertinib. His best corrected visual acuity was 0.15, and IOP was 52 mmHg in the left eye. Anterior chamber cells (+), numerous small nodules in the iris, and small masses in the inferior angle were observed. In the aqueous humor, the CEA level was higher than in the blood. Napsin A and Thyroid Transcription Factor-1 (TTF-1) positive cells showed in the resected tissue at iridectomy performed during trabeculectomy. The pathological diagnosis of metastatic iris tumor of the lung adenocarcinoma was made, and we injected bevacizumab intravitreally once and continued Osimertinib. His IOP lowered to 8-10 mmHg, and the iris masses disappeared. He lost vision by metastasis to the left optic nerve after termination of Osimertinib one and a half years later. The metastasis shrank after restarting the drug. He passed away from an exacerbation of his primary lung cancer two years and nine months after the first visit. Although he lost vision in his left eye, the metastatic tumor in his left eye and optic nerve had disappeared, and his quality of life was maintained without any pain in his eye.

Conclusions: Checking tumor markers in the aqueous humor can aid in diagnosis, and aggressive treatment of metastatic iris tumors must help maintain patients' Quality of Life.