Unmasking adenoid cystic carcinoma on lip mimicking as reactive lesion – A case report and review of literature

ABSTRACT Rationale: Among salivary gland malignancies, adenoid cystic carcinoma (ADCC) is a particularly uncommon entity in the lip region, representing approximately 1% of malignant neoplasms in the head and neck. This case highlights the clinical and histopathological features of lip ADCC, as well as the utility of immunohistochemistry (IHC) in confirming the diagnosis. Patient Concerns: A 51-year-old male presented with a 2-year history of persistent swelling in the upper lip and complaints of an ill-fitting upper removable partial denture. A solitary ulcer was observed centrally on the swelling. Diagnosis: Histopathological examination of the excised lesion confirmed the diagnosis of adenoid cystic carcinoma. Interventions: A wide local excision of the upper alveolus was performed after excisional biopsy. Outcomes: At the 6-month postoperative follow-up, the patient exhibited no signs of recurrence or distant metastasis. Lessons: Adenoid cystic carcinoma can clinically mimic benign lesions, leading to potential delays in diagnosis. Due to its aggressive nature and perineural invasion, early histopathological evaluation and the use of IHC are crucial in guiding accurate diagnosis and effective treatment planning, especially in rare presentations such as lip involvement.