Diagnostic Challenges in a Rare Submandibular Epidermoid Cyst Transforming into Squamous Cell Carcinoma - A Case Report.

RATIONALE: Submandibular gland epidermoid cyst is extremely rare and malignant transformation into squamous cell carcinoma (SCC) is even rarer. No such case report is published.

PATIENT CONCERNS: A 49-year-old female reported with a large, slowly growing left-sided neck swelling present for two years. Her primary concern was large swelling.

DIAGNOSIS: Clinical finding, cytology and imaging were suggestive of 'Epidermoid Cyst of Submandibular Gland'. Intraoperative frozen section and post-operative definitive histopathological examination (HPE) revealed malignant transformation into SCC.

TREATMENT: In toto surgical excision was performed. Once the frozen section HPE confirmed transformation into SCC, clearance of 4-6 mm margin and modified supraomohyoid neck dissection was completed.

OUTCOME: No sign of recurrence on 1-year postoperative follow-up.

TAKE-AWAY LESSON: This case is unique of its kind without any previous literature report. In case of large and rapidly growing submandibular gland lesion, possibility of malignant transformation should not be overruled.