A 70-year-old Korean female was referred to our oral and maxillofacial department with recurrent keratosis in the lower lip over the course of 3 years. She was diagnosed with oral lichen planus (OLP) in another hospital 2 years prior and received a corticosteroid application without complete symptom relief. The patient looked healthy without any other skin or oral mucosal diseases and had her natural dentition without any removal dentures or prosthetics replacing her anterior teeth on both the maxilla and mandible. The patient also had no history of smoking, alcohol consumption, or hospitalization. Her occupation over the past 30 years involved selling crabs in a large fish market; thus, she often smelled fresh crabs and tasted marinated and seasoned crabs. The hyperkeratotic white plaque lesion was round and superficial in the lower middle lip site. The patient desired surgical examination after its location altered to the lateral side. A superficial excisional biopsy was performed, and an initial stage of SCC was revealed. We hypothesized that OLP transformed into malignancy due to chronic irritation of her lower lip. Therefore, additional cancer work-ups such as supplemental images like computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography-computed tomography (PET-CT) were obtained. No metastasis, significant hypermetabolic lesion in the neck, or remaining suspicious lesions were observed in these examinations. After the first excisional biopsy, a keratotic whitish plaque lesion suspicious of recurrence appeared on the patient 6 months later. After having a consent form for operation, we performed a wide V-shaped wedge resection. Superficial lip mucosa with underlying orbicularis oris muscles were excised with a 5.0-mm safety margin on the lip surface, and direct closure with layered sutures was performed after negative margin confirmation in frozen biopsy. The specimen was sent to the Department of Oral Pathology at GangneungWonju National University Dental Hospital and fixed, embedded with paraffin, and microsectioned at 4-μm thickness for pathologic diagnosis. The microsections were routinely stained with hematoxylin and eosin and observed under ordinary light microscopy (U-POT®, Olympus Co., Japan). The microscopic images were captured by a digital camera (DP-70®, Olympus Co., Japan) and analyzed for the article submission under the approval of the Institutional Review Board of Seoul National University (S-D2017006). The microsection exhibited normal architecture of lip mucosal epithelium and fibromuscular adipose tissue containing minor salivary glands (MSGs). The MSGs showed marked ductal hyperplasia with inflammatory cell infiltration. The epithelial tumor became severely keratinized and exhibited comedo-type necrosis and luminal sequestration of the keratinized epithelium mimicking the glandular duct structure, and the tumor cells were relatively well-localized and typically surrounded by abundant lymphoid tissue. Some areas of keratinized tumor epithelium showed the typical features of epimyoepithelial islets seen in Mikulicz disease, and some tumor epithelium formed pseudo-ductal structures with active lymphocytic reactions under high magnification. The pathologic lesion was confined to the vermilion border without the involvement of the oral mucosa or orbicularis oris muscle with a 2-mm lesion depth. In the periphery region, the tumor cells did not grow invasively, but proliferated in a budding and branching fashion similar to glandular ductal growth. In cytokeratin immunostaining, the keratinized tumor epithelium seemed to float in the lymphoid stroma with no feature of infiltrative growth into adjacent fibromuscular adipose tissue. Therefore, this lesion was finally diagnosed as lower lip EC originating from AC. The patient was instructed to avoid any trauma to her lips and exhibited a favorable outcome during the 5-year follow-up period.