Primary mucinous carcinoma of the lower eyelid treated with wide excision and postoperative radiotherapy: a case report and literature review.

Primary cutaneous mucinous carcinoma (PCMC) is a rare malignant neoplasm that originates from the deepest part of the eccrine sweat glands. Characterized by slow growth, PCMC often appears on the head and neck of older patients. Although it rarely metastasizes, its high recurrence rate leads to significant morbidity. Clinically differentiating PCMC from benign tumors is challenging due to its slow growth and asymptomatic nature, and a biopsy is often required for a definitive diagnosis. A 77-year-old man presented with a non-tender lesion on his left lower eyelid that had been gradually progressing over a decade. The lesion was excised, and histological examination confirmed it as PCMC. A positron emission tomography-computed tomography scan conducted to differentiate between primary and metastatic cancer showed no abnormal findings. Computed tomography was then performed to assess the remaining primary site, followed by a wide excision. The frozen biopsy revealed no cancer in the margins from five directions; however, the permanent biopsy confirmed the presence of cancer in the base margin. After consultation with the hematology-oncology department, the patient underwent additional radiation therapy. One year post-surgery, there were no signs of recurrence.