.

1. Polymorphous
adenocarcinoma

2. Definition
Polymorphous adenocarcinoma (PAC) is a malignant epithelial tumour
characterized by cytological uniformity, morphological diversity, and an
infiltrative growth pattern.

3. Epidemiology
• the second most common intraoral malignant salivary gland tumour,
accounting for 26% of all carcinomas at this site.
• The female-to-male ratio is about 2:1
• The patient age ranges from 16 to 94 years, with a mean of 59 years.
• More than 70% of patients are aged 50-70 years.

4. Localization
Approximately 60% of PAC cases in palate. Other intraoral locations are
the buccal mucosa, retromolar region , upper lip, and base of tongue.
Uncommon locations include the major salivary and lacrimal glands,
nasopharynx, and nasal cavity.
Almost exclusively a tumour of minor salivary glands, with over 60%
arising in the palate. The remainder usually occur in the buccal mucosa
or upper lip.

5. Clinical features
PACs typically present as a painless mass of variable duration.
Bleeding, telangiectasia, and ulceration of the overlying mucosa may
occasionally be found.

6. Histopathology
PAC is typically submucosal in location and unencapsulated. The
tumour histopathology is characterized by cytological uniformity,
histological diversity, and an infiltrative growth pattern.
Neoplastic cells are small to medium-sized and uniform in shape, with
bland, minimally hyperchromatic, oval nuclei.

8. • Mitoses are uncommon and necrosis is seen in high-grade
transformation.
• A prominent feature is the wide variation of morphological
configurations within and between tumours.
• The main microscopic architectural patterns are lobular, trabecular,
microcystic or cribriform (as in adenoid cystic carcinoma), solid, and
papillary-cystic.

10. • Tumour stroma can be mucinous or hyalinized.
• Perineural involvement is common .
• Invasion into adjacent bone may be seen in tumours of the palate

12. Perineural invasion:
(N) Between the affected
nerves
(C) is a cribriform island

13. The tumour cells are immunoreactive for cytokeratins (e.g. CK7, in
100% of cases).
S100 protein (in 97%), CEA (54%), GFAP (15%) , MSA (13%), and EMA
(12%).
mammaglobin is positive in 67-100% of tumours.
Staining for p63 is reported in 100% of cases, whereas p40 is
consistently negative.
KIT (CD117) positivity has been described in about 60% of tumours.

14. IHC
CD117 (c-kit), GFAP and myoepithelial markers (e.g. calponin, SMA,
p63, SOX10)
Polymorphous adenocarcinoma is usually negative for GFAP, and only
occasional cases are positive for myoepithelial markers as
(calponin, SMA) or CD117 (c-kit)
p63 however is usually positive, but p40 is consistently negative.

15. Genetic profile
A variety of molecular and genetic findings have been re ported in PAC ,
among these are HRAS mutations. Including alterations of the PRKD
gene family.

16. Prognosis and predictive factors
The overall survival of patients with PAC is generally good. A review of
large series with long term follow- up found local recurrence rates of
10-33% (average: 19%).
Of these, 50% occurred 5 years after initial diagnosis. The range of
reported regional metastasis rates is 9-1 5%.