The existence of early stage oral mucosal melanoma: A 10-year retrospective analysis of 170 patients in a single institute

Abstract

Background: Oral mucosal melanoma (OMM) is an aggressive tumor with an extremely low incidence, and the current TNM Staging System has classified all OMMs as high stage. However, controversy remains regarding the existence of early stage OMMs.

Patients and methods: The clinical and pathological features, treatments and outcomes of 170 OMM patients treated in a single institution from January 2007 to July 2017 were retrospectively analyzed. Multivariate analysis was performed to identify significant prognostic factors for overall survival (OS).

Results: Multivariate analysis identified positive cervical lymph nodes (p < 0.0001), nodular OMMs (p < 0.0001), ulceration (p = 0.002), and level III or level IV invasion (p < 0.0001) as independent poor prognostic factors for OS. Nodular OMM patients with a tumor size ≤1 cm had a better outcome than those with a tumor size >1 cm (p < 0.0001). Twenty-two patients with superficial invasion had a favorable survival without the need of adjuvant therapy (postoperative chemotherapy or radiotherapy), and the current TNM Staging System was not suitable for those patients. Patients with deep invasion were more likely to suffer from recurrence and distant metastasis.

Conclusions: Tumor size ≤1 cm and OMM in situ, although extremely rare, do exist. It is advisable for AJCC to consider tumor size ≤1 cm and OMM in situ as the early stage of OMM when updating the new Oral Melanoma Staging System.

Keywords: Invasion level; Melanoma; Oral; TNM Staging.