Primary mucinous adenocarcinoma of the eyelid: A case with initial clinical misdiagnosis requiring surgical re-excision of the tumor

INTRODUCTION AND IMPORTANCE: Primary mucinous adenocarcinoma (PMA) of the skin is a rare condition that is usually seen in elderly patients, most commonly involves the periorbital region as a slow growing mass. Histopathological and immunohistochemical (IHC) stains are of paramount importance for the diagnosis of these lesions, which are usually misdiagnosed either as benign or metastatic mucinous adenocarcinomas. CASE PRESENTATION: We herein report a rare presentation of PMA in a 70-year-old male patient who presented with an upper eyelid residual lesion after being incompletely excised elsewhere as an epidermal cyst and was successfully managed by complete surgical excision with frozen section control of the margins and no evidence of recurrence. DISCUSSION: PMA is a rare sweat gland malignancy that involves the eyelid in 41.9% in the head and neck area and is a disease of the elderly with median age of 60 years and variable reported racial and gender predilection. Diagnosis of PMA is challenging both clinically and histopathologically, which was the case in our patient's initial incomplete excision with the presumed diagnosis of a benign epidermal cyst. Proper final tissue diagnosis and surgical management in our patient ensured his favorable outcome. CONCLUSION: Accurate diagnosis of PMA requires a high index of clinical suspicion and accurate histopathological diagnosis aided by proper IHC markers.