True about salivary gland tumour is:
Treatment and Prognosis 
The treatment of mucoepidermoid carcinoma is predicated by the location, histopathologic grade, and clinical stage of the tumor. Early-stage tumors of the parotid often can be treated by subtotal parotidectomy with preservation of the facial nerve. Advanced tumors may necessitate total removal of the parotid gland, with sacrifice of the facial nerve. Submandibular gland tumors are treated by assured surgical excision. For low-grade neoplasms, only a modest margin of surrounding normal tissue may need to be removed, but high-grade or tumors warrant wider resection, similar to that required for squamous cell carcinomas. If there is underlying bone destruction, then the involved bone must be excised. 
 
Adenoid cystic carcinoma is a relentless tumor that is prone to local recurrence and eventual distant metastasis. Surgical resection is usually the treatment of choice. Adjuvant radiation therapy may slightly improve patient survival in some cases, although recent SEER data suggest that radiation therapy does little to improve prognosis overall. Because metastasis to regional lymph nodes is uncommon (6% to 10% of cases), neck dissection usually is not indicated. 
Ref: Oral pathology Neville, 4th ed page no 457, 463
MEC shows perineural spread and requires wide resection
ACC shows perineural spread and requires wide resection
MEC is well-encapsulated and does not require surgical excision
ACC is well-encapsulated and does not require surgical excision