The submandibular gland (SMG) is sacrificed during neck dissection in patients undergoing curative surgery for oral squamous cell carcinoma (OSCC). This may cause a decrease in the production of saliva and result in xerostomia.

This study aimed to determine the incidence, invasion patterns, risk factors, and prognosis of SMG involvement in OSCC.

The primary predictor variable in this study was SMG involvement, and the secondary predictor was prognosis.

The primary outcome variables were patient characteristics and pathological results for extranodal extension (ENE), perineural invasion (PNI), and pN stage. Four out of 173 patients (2.23 %) showed SMG involvement. Of these cases, one (25 %) was from the primary lesion and three (75 %) were from the metastatic neck lymph nodes (LNs). The primary lesion was located on the lower gingiva, and the other three were from level-Ib LNs with ENE. The pathological PNI was observed in three of the four patients, and ENE was observed in three of the four patients. Preoperative CT and MR revealed SMG invasion and contact in two patients. There were significant differences in the ENE and pN stages between patients with and without SMG involvement (P<0.05). There was a significant difference in the overall survival between patients with (25.0 %) and without (71.5 %) SMG involvement (P = 0.011).

SMG involvement was associated with ENE, pN stage, and poor prognosis.