A diverse array of epithelial tumours have been described in the salivary glands (11 benign and 21 malignant types in the current Who classification). Only the more common ones will be mentioned here.

 Pleomorphic adenoma

 • Most common salivary gland neoplasm.

 • Majority occur in the parotid gland as a painless, slowly growing lump.

 • Cytology is cellular with abundant epithelial and myoepithelial cells and f ibrillary stromal fragments.

• histology shows a circumscribed tumour composed of a mixture of ductal epithelium, myoepithelial cells, and a myxochondroid stroma. (Fig. 1).

• Benign tumour but may recur following incomplete excision. If left untreated, there is a small risk (6%) of malignant transformation (‘carcinoma ex pleomorphic adenoma’).

• Metastasizing pleomorphic adenoma is histologically indistinguishable from pa but produces secondary tumours in distant sites (bone, lung, lymph nodes). More common if after multiple local recurrences.

pleomorphic adenoma. typical microscopic appearance of a pleomorphic adenoma with an intermingling of epithelial elements (arrow) set within a mesenchymal component. reproduced with permission from Clinical Pathology (Oxford Core texts), Carton, James, daly, richard, and ramani, pramila, Oxford University press (2006), p.456, Figure 19.7.

Warthin tumour

• Second most common salivary gland neoplasm.

 • almost all occur in the parotid gland as a painless, slowly growing lump. May be bilateral and linked with smoking.

 • Cytology shows sheets of oncocytic epithelial cells with abundant lymphoid cells in the background.

 • histology shows a circumscribed tumour composed of papillary- cystic structures lined by a double layer of oncocytic epithelium with an underlying dense lymphoid stroma.

 • Benign tumour but may recur following incomplete excision.

 Mucoepidermoid carcinoma

 • Most common malignant salivary gland neoplasm.

 • Wide age range and the commonest malignancy in children and young adults.

 • presents with a tender mass related to a major salivary gland, but can occur in minor glands.

 • Cytology shows mucus, intermediate cells, and mucus cells.

 • histology shows an infiltrative tumour composed of a mixture of intermediate, squamoid, and mucous cells. Cystic change may be seen.

 • Most are characterized by CRTC1-MAML2 gene fusion.

 • Most tumours are low- grade and behave well, with survival >95%.

 • high- grade tumours are aggressive, with 10- year survival ~25%.

 Acinic cell carcinoma

 • Malignant salivary gland tumour, mostly arising in the parotid (90%).

 • presents with a mass which may be painful.

 • histology shows a tumour composed of serous acinar cells with granular cytoplasm which may grow in a variety of architectural patterns (solid, microcystic, follicular).

 • 20- year survival ~90%.

 Adenoid cystic carcinoma

 • Malignant salivary gland tumour, mostly arising in major salivary glands, but >1/ 3rd occur in minor glands.

 • presents with a slowly growing mass which may be painful and mean age 50 years.

 • histology shows an infiltrative tumour composed of basaloid epithelial and myoepithelial cells, classically forming cribriform sheets, tubules, or solid sheets surrounded by a hyalinized basement membrane. perineural invasion is very frequently seen.

 • Fusion of the MYB/MYBL1 oncogene and the transcription factor NFIB.

 • the tumour shows a relentless clinical course, with a 10- year survival rate of 50– 70%. distant metastases reported in >50%.

Polymorphous adenocarcinoma

 • Second commonest intraoral malignant salivary neoplasm. average age 50–70 years.

 • Most involve the palate and present as painless mass.

• Submucosal and composed of cytologically uniform cells with a diverse morphology (lobular, trabecular., microcystic, solid, cribriform with perineural invasion).

 • Good overall survival, but local recurrence can occur in 10– 33%.

 Salivary duct carcinoma

 • aggressive malignancy resembling mammary ductal carcinoma.

 • 10% of all salivary gland malignancies, usually male and elderly.

 • Most occur in parotid and often rapidly growing with facial nerve palsy, pain, and metastatic disease.

 • histology shows high- grade ductal carcinoma with comedonecrosis, lymphovascular, and perineural invasion.

• Often express androgen receptor and 25– 30% express her2.

 • 35–45% 5-year survival.

Secretory carcinoma

 • Low- grade salivary carcinoma, arising predominantly in the parotid gland with a morphological resemblance to mammary secretory carcinoma.

 • Mean age 46 years, most commonly presents with a painless mass in the parotid.

• histology shows an epithelial tumour with solid, cystic, or papillary growth and eosinophilic secretions.

 • harbours a t(12;15) translocation, leading to an ETV6- NTRK3 fusion oncogene.

• Indolent tumour, rarely distant metastases with 85% 5- year survival.