AMELOBLASTOMA

 

AMELOBLASTOMA (ICD CODE 9310/0)

• It is an ondontogenic tumor which is slow growing, locally invasive neoplasm which has tendency to recur

• Age– can occur at any age but rare in children and more common in 3rd to 7th decades of life 

• Sex – equal in both sexes

• Site – 

  • Common site is mandible (85% of cases), usually at molar ascending ramus area. Next common site is maxilla (15% of cases), at the posterior region

  • Other sites – soft tissue of retromolar area and posterior gingiva,

  • Rare sites – Temporal bone, infratemporal fossa, middle ear, sinonasal tract 

• Origin – Odontogenic epithelium and from remnants of dental lamina in gingiva ( rests of Serres)

• Clinical presentation –

  • Usually asymptomatic or may presents as painless swelling with slow growth

  • If the tumor is large, patient may have malocclusion or may have facial deformity 

  • Radiography – presents as multilocular radiolucent lesion with cortical expansion

• Microscopy – 

• Different histological patterns are seen. They are 

  • Follicular pattern

    • Nests of epithelium resembling enamel organ of developing teeth, which are dispersed in fibrous stroma

    • core of the nest show loosely arranged angular cells that resemble the stellate reticulum

    • Central core is surrounded by single layer of tall columnar ameloblast like cells

    • Nuclei shows reverse polarity and they are placed away from the basement membrane

    • Cytoplasm shows subnuclear vacuolation

    • Squamoid differentiation can also be present

    • Cysts formation may be present which may vary from small microcysts to large macrocysts

  • Plexiform type of ameloblastoma

    • Anastomosing cords or large sheets of odontogenic stellate epithelium bound by ameloblastic cells with similar stellate reticulum like core.

    • In this variant reverse polarity may not be seen in some case
      

  • Other rare variants are 

    • Basal cell variant – stellate reticulum cells are replaced by basaloid cells 

    • Granular cell variant – stellate reticulum cells have eosinophilic granular cytoplasm

    • Acanthomatous variant – stellate reticulum cells have keratinization and squamous metaplasia

    • Desmoplastic variant – increased fibrous stroma with compressed epithelial islands  

  • Cystic ameloblastoma may have columnar cells with reversed polarity and cytoplasmic vacuolation lining the cystic cavity

• Immunohistochemistry 

  • Tumor cells are positive for – CK5, CK14, CK19, CD 56, p63, p40, BRAF V600E, Beta catenin, Calretinin, FOXP1

• Treatment 

  • Surgical resection with margins resection 1cm past the radiographic level of tumor because the actual margin of tumor usually extends beyond the radiographic or clinical margin

  • It has high recurrence rate usually upto 15%

Reference

• David E. Spence and Samir K. E I.Mofty. Tumors and cysts of the jaws. In: the Washington manual of Surgical Pathology. Second edition. By: Peter A. Humphrey, Louis P. Dehner, John D. Pfeiffer