Clinicopathological and immunohistochemical characteristics of pigmented oral squamous cell carcinoma.

Pigmented oral squamous cell carcinoma (POSCC) is a rare and underrecognized pathological variant of oral squamous cell carcinoma (OSCC). The current study aimed to evaluate the clinicopathological characteristics, treatment outcomes and prognosis of patients with POSCC and to investigate its oncological properties using immunohistochemical studies. A total of 1,512 patients were pathologically diagnosed with squamous cell carcinoma of the oral cavity, and were treated at the Department of Oral and Maxillofacial Surgery, Tokyo Medical and Dental University between January 2001 and December 2018. A total of 25 patients had POSCC and underwent radical surgery. Of these 25 patients, 23 presented with early T stage disease. Additionally, 22 patients were negative for cervical lymph nodes metastasis. Only one patient had local recurrence. The 5-year disease-free and disease-specific survival rates were 86.6 and 95.8%, respectively. Immunohistochemically, a high percentage of POSCC exhibited low p53 and Ki-67, preserved E-cadherin or negative vimentin expression. The results suggested that POSCC tends to exhibit non-aggressive oncological behavior and demonstrates a good prognosis.