Early Recurrence of Non-neuroendocrine Primary Cutaneous Mucinous Carcinoma of the Eyelid After Surgical Excision: A Case Report.

Primary cutaneous mucinous carcinoma (PCMC) is a rare malignant cutaneous adnexal neoplasm prone to local recurrence. Neuroendocrine differentiation has been recognized in a subset of these tumors, and emerging evidence suggests that its presence may be associated with differences in clinical behavior and prognosis. Reports characterizing neuroendocrine differentiation in eyelid PCMC remain limited. A 47-year-old man underwent excision of a chalazion-like mass of the right upper eyelid at another clinic, and histopathologic examination revealed mucinous carcinoma. Systemic evaluation found no extracutaneous primary malignancy. Although no residual lesion was clinically apparent at referral, a full-thickness excision approximately 7 mm in total width was performed at the presumed primary site. Histopathologic examination demonstrated residual mucinous carcinoma within the orbicularis muscle, with negative surgical margins. Four months later, firm nodules developed on both sides of the surgical scar, and local recurrence was confirmed. The recurrent lesions were treated with wide full-thickness excision using 7-8 mm clinical margins, and intraoperative frozen-section analysis confirmed negative margins. Staged eyelid reconstruction followed. Immunohistochemistry was negative for synaptophysin and chromogranin A, whereas insulinoma-associated protein 1 (INSM1) showed only focal weak positivity. Gross cystic disease fluid protein-15 (GCDFP-15) was partially positive, while GATA binding protein 3 (GATA3), estrogen receptor, and progesterone receptor were positive. The overall immunophenotype supported apocrine (breast-like) differentiation without significant neuroendocrine differentiation, consistent with non-neuroendocrine PCMC. No recurrence was observed during 36 months of follow-up. This case suggests that histologically negative margins may not exclude occult residual disease when the original tumor site is uncertain. Careful surgical planning, appropriate margin assessment, and long-term surveillance may be warranted because occult residual disease or subclinical tumor spread may contribute to early recurrence.