Abstract
Tumors of salivary glands forms 3% of all tumors. Majority of them is benign, parotid gland is most commonly involved.
Risk of malignity is increasing with reduced size of involved gland. Clinical differentiation of salivary gland tumors is difficult.
MRI is therefore important in differential diagnosis. Ultrasound is first method of choice in diagnostics of pathological involvement of salivary glands.
MRI is preferred for evaluation of foci involving deep lobe of parotid gland, sublingual gland, minor salivary glands, deeply placed soft tissue and lymphatic nodes and perineural spread. Pleomorphic adenoma is the most common tumor of salivary glands, mostly in superficial lobe with fibrous capsule.
Carcinoma, usually multifocal, can develop later from adenoma. Inhomogeneity of parenchyma with solid and cystic portions, mild enhancement after Gadolinium chelate application, higher wash out ratio and lower mean ADC value than in malignant tumors are characteristic for Warthin tumor, involving largely smokers.
Mucoepidermoid carcinoma of lower grade can mimic pleomorphic adenoma, higher grade carcinoma often metastasize to lymphatic nodes. Adenoid cystic carcinoma often spreads perineuraly, makes recurrence in long delay after surgery.
It has intermediate T2W signal, higher grade of tumor has even low T2W signal. Metastases into salivary gland are exceptional, commonly from lung and breast carcinoma, from skin squamous cell carcinoma or melanoma.
Multiple small cystic structures in parenchyma of gland are characteristic for Sjógren syndrome. Lymphoma can involve lymphoid tissue of parotid gland or adjacent lymphatic nodes, either primary or secondary by systemic involvement.