Pleomorphic adenoma — salivary gland FNA cytology
Author: Faruk Skenderi, MD, PhDReviewed by: Semir Vranić, MD, PhDLast reviewed:
- Faquin WC, Rossi ED, Baloch Z, et al., eds. The Milan System for Reporting Salivary Gland Cytopathology. 2nd ed. Springer; 2023.
- Rossi ED, Baloch Z, Pusztaszeri M, Faquin WC. The Milan System for Reporting Salivary Gland Cytopathology (MSRSGC): an ASC-IAC-sponsored system for reporting salivary gland fine-needle aspiration. J Am Soc Cytopathol. 2018;7(3):111-118. https://doi.org/10.1016/j.jasc.2018.02.002 (opens in new tab)
- Saoud C, et al. Pitfalls in salivary gland cytology. Acta Cytol. 2024;68(3):194-205. https://doi.org/10.1159/000538069 (opens in new tab)
The commonest salivary gland tumour and the commonest pitfall on FNA. A pattern-based checklist for confident diagnosis and Milan System categorisation.
- Classic triad on smears: epithelial/myoepithelial cells, fibrillary chondromyxoid stroma, and bland spindled myoepithelial cells embedded in the matrix.
- Chondromyxoid stroma is fibrillary, magenta on Diff-Quik, pale green/grey on Papanicolaou — fronds with frayed edges, not sharply defined globules (cf. adenoid cystic carcinoma).
- Epithelial cells form cohesive sheets and branching groups; myoepithelial cells are plasmacytoid, spindled, or stellate.
- Milan System category IVa — benign neoplasm; ROM ~3–5%, management is surgical excision (superficial parotidectomy).
- Key pitfalls: cellular pleomorphic adenoma vs myoepithelioma vs basal cell adenoma; scant stroma cases mimic basaloid neoplasms.
- Beware adenoid cystic carcinoma: sharply circumscribed acellular hyaline globules, uniform basaloid cells, higher N:C ratio — different management.
- Carcinoma ex pleomorphic adenoma clues: necrosis, marked atypia, mitoses, or a discordant cellular focus in an otherwise classic PA — flag for excision and complete histology.