Pleomorphic Adenoma: A well defined encapsulated nodule consisting of sheets and nodules of cytologically bland ductal and plasmacytoid elements. (epithelial-myoepithelial elements). There are occasional foci of duct formation. This is arranged in a myxofibrillary matrix.
- Completeness of excision
- Evidence of atypia/malignancy (?carcinoma ex pleomorphic adenoma)
- Adjacent salivary tissue? obstructive changes
- Intraparotid lymph nodes
Warthin Tumour: An encapsulated tumour on showing lymphoid stroma, cystic change and intraluminal papillary epithelial projections. The papillae have a bilayer of oncocytic epithelium overlying a lymphoid stroma with germinal centers.
Acinic cell carcinoma: A slowly enlarging mass in the parotid region with serous acinar cell differentiation. Acinar cells are large, polygonal cells with lightly basophilic granular cytoplasm and round eccentric nuclei. Cytoplasmic zymogen granules DPAS positive. Vacuolated cells contain clear cytoplasmic vacuoles.
Adenoid cystic carcinoma: Basaloid tumour consisting of epithelial and myoepithelial elements. Architecuturally may be tubular, cribriform or solid. Cribriform is the most common with mucopolysaccaride filled spaces. Perineural invasion common. May invade bone extensively. Duct cells +ve for CD117, basal cells for actin S100.
Basaloid neoplasms differential diagnosis:
- Basal cell adenoma
- Epithelial-myoepithelial carcinoma
- Basaloid squamous cell carcinoma
- Basal cell adenocarcinoma
- Adenoid cystic carcinoma
- Polymorphous low grade adenoca
Mucoepidermoid carcinoma: Characterised by squamoid (epidermoid), mucus producing and cells of intermediate type. Architecture varies. Positive for mucicarmine/alcian blue. Grades low, intermediate & high – cystic component<20%, neural invasion, necrosis, >4mitoses/10hpf, anaplasia.
Polymorphous low grade adenoca: A relativelly indolent malignancy, most cases arising from the minor salivary glands. Althought the tumour cells tend to be cytologically bland and monomorphic, it can form a wide variety of archictural patterns and infiltrative growth pattern.
Lymphoepithelial carcinoma: Undifferentiated carcinoma accompanied by a prominant non-neoplastic lymphoplasmacytic infiltrate. High incidence in China where EBV is implicated as an aetiological agent.
Basal cell adenoma: Benign basaloid appearance of tumour cells and absence of myxochondroid stroma. Tubular type and membranous type (prominent hyaline material)
Oncocytoma: Benign tumour composed exclusivelly of large epithelial cells with characteristic bright eosinophilic granular cytoplasm.
WHO classification of tumours. Head and Neck tumours.
Robbins and Cotrans. Pathological Basis of Disease.