Table 1 Differential diagnosis of juvenile pleomorphic adenoma of the cheek

Adenoid cystic carcinoma

- Cribriform and pseudoglandular patterns of basaloid cells with hyalinized stroma

- Frequent perineural invasion

- Minimal nuclear pleomorphism

- No squamous differentiation

- No high grade dysplasia or squamous carcinoma in situ, no extensive necrosis

Polymorphous low grade adenocarcinoma

- Uniform plump columnar cells with bland nuclei arranged in variable growth patterns (tubular, cribriform, papillary, solid, fascicular, microcystic, single file, pseudoadenoid cystic, strand-like, mixed)

- Perineural invasion common around small nerves

- Infiltrative borders

Basal cell adenoma

- Elongated and branching canaliculi separated by hyaline stroma

Acinic cell carcinoma

- Variable cell types (serous, clear, vacuolated, intercalated duct cells) arranged in solid, microcystic, papillary cystic and follicular patterns

- few mitotic figures

Clear cell carcinoma-hyalinizing type

-Trabeculae, cords, islands or nests of monomorphic clear cells surrounded by hyalinized bands with foci of myxohyaline stroma

Cystadenocarcinoma

- Invasive, cystic growth pattern, 75% had

- Conspicuous papillary component

- Composed of small cuboidal cells, large cuboidal cells, tall columnar cells or mixture

- Cystic spaces with hemorrhage and granulation tissue are frequent

Intraductal carcinoma

- intraductal neoplasm with micropapillary, cribriform, solid, comedo or clinging patterns, with preservation of myoepithelial cells surrounding intraductal tumor

Mucoepidermoid carcinoma

- Cords, sheets, clusters of mucous, squamous, intermediate and clear cells; low to high grade

Epithelial myoepithelial carcinoma

- Both epithelial and myoepithelial components seen

- Most tumor cells have myoepithelial features with clear cytoplasm or naked nuclei

- Focally, there are ducts or tubules with an outer rim of myoepithelial cells and inner, dark ductal cells with scant eosinophilic cytoplasm and round, bland nuclei