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Polymorphous adenocarcinoma

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Polymorphous adenocarcinoma

  1. 1. Polymorphous adenocarcinoma
  2. 2. Definition Polymorphous adenocarcinoma (PAC) is a malignant epithelial tumour characterized by cytological uniformity, morphological diversity, and an infiltrative growth pattern.
  3. 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. 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. 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. 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.
  7. 7. • 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.
  8. 8. • Tumour stroma can be mucinous or hyalinized. • Perineural involvement is common . • Invasion into adjacent bone may be seen in tumours of the palate
  9. 9. Perineural invasion: (N) Between the affected nerves (C) is a cribriform island
  10. 10. 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.
  11. 11. 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.
  12. 12. 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.
  13. 13. 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%.

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