Tuesday, January 6, 2015

Ameloblastoma Complete Info (with Pictures)

 

Definition

Ameloblaatoma is a benign locally aggressive neoplasm arising from the odontoenic epithelium and it is the most common odontogenic neoplasm of the oral cavity.


Etiology

Exactily not known however , the following factors may predispose the formation of ameloblastoma:

  • Trauma.
  • Infection.
  • Previous inflammation.
  • Extraction of tooth.
  • Dietary factors.
  • Viral infection.


Clinical Features

  • Incidence Approximately 1 percent among all oral tumous.
  • Age- second, third,fourth and fifth decade of life , the mean age of occurrence is about 32 years. This lesion occurs more commonly in blacks than whies.
  • Sex-  Males are affected more often females.
  • Site- Ameloblastoma in most of the cases involve the mandible (80%), especially in the molar-ramus area (70%) , although some lesions may develop in the premolar (20%) or symphysis (10%) regions.
  • Maxillary tumors also commomly involve its posterior part  and the lesions ofter have a tendency to invade into the antrum (15%) or the nasal floor.
  • Extraosseous ameloblastomas can rarely occur mostly in relation to the gingival.


Clinical Presentation


  • Clinically ameloblastoma commonly presents a slow enlarging,painless,ovoid or fusiform,bony hard swelling of the jaw.
  • The lesion causes expansion and didtortion of the cortical plates of the jawbone and displacement of the regional teeth; these are often leading to gross facial asymmetry.
  • Pain ,paresthesia and mobility of the regional teeth may be present in few cases.
  • Most of the be patients report with a typical long time history of presence of an “abscess” or a “cyst” in the jow bone that was operated on several occasions but has recurred after each attempt.
  • Lerger lesions of ameloblastoma often cause severe expansion ,destruction and thinning of the cortical plates , which often result in “fluctuation”or “egg shell cracling” of the affected bone.
  • Pathological fractures”,may occur in many such affected bones.
  • The mucosa overlying the tumor appears normal and the regional teeth are usually vital.
  • In some cases , smaller lesions may remain asymptomatic for a longer duration of time and are detected incidentally during routine radiographic examinations.
  • Many untreated lesions may reach to an enor –mous size with time.
  • Sometimes larger lesions may perforate the cortical plates and protrude outside the bone as a modular mass.
  • Maxillary tumors can invade into the maxillary air sinus and extend further up to the orbit or the nasopharynx;thereby or nasal obstruction,etc.
  • Some of the lesions may progress to ethmoidial air sinuses or even up to the cranial base.
  • Extraosseous ameloblastoma often produces a small ,nodular growth in the gingival.


Radiological Feature

  • Radiographically ameloblastoma usually pre-sent a well-defined,multilocular ,radiolucent area in the bone with a typical “honey-comb” or “soap-bubble” appearance. Few lesion can be unilocular too.
  • The lerger lesions often couse expansion,dis-tortion or even perforation of the cortical plates.
  • In radiograph the lesion typically exhibits an irregular and “scalloped”margin. 
  • Resorption of the adjoining normal teeth is often seen in rapidly growing lesions.
  • Ameloblastoma can cause expansion of the lower border of mandible. An irregular,”scallo-ped margin “ are often the typical features of ameloblastoma.
  • An the neoplasm progresses it sometimes become associated tooth (mostly the third molars) and in such cases the lesion may be resemble a dentigerous cyst.


Differential Diagnosis

  • Odontogenic keratocyst (Primordial cyst)
  • Dentigerous cyst
  • Central giant cell granuloma
  • Central hemangioma
  • Aneurysmal bone cyst
  • Fibromyxoma.


Macroscopic Features

  • On naked eye examination the tumor presents a cylindrical or fusiform swelling, which expands the bone so the severely that it can bebroken by digital pressure (egg-shell crrackling).
  • Perforation of the bone with subdequent protrusion of the tumor outside the bony wall is often noticed.
  • Cut section of ameloblastoma often appears as a “grayish-white”mass ,which contains some ‘cyst-like ‘ spaces. However no calcified is usually found within the tumor.
  • Some lesions are made up entirely of solid tissue mass although most of them have some cystic spaces of varying size within them.
  • Some intratumor cysts are large and contain either a straw colored fluid or a semi solid gelatinous material.
  • Sometimes one or two teeth may be present within thw lesion.


Histopathological Features

Histologically ameloblastoma shows neoplastic proliferation of odontogenic epithelial cells mostly in two distinct patterns ; (i) Plexiform type and (ii) Follicular type.


Plexiform Ameloblastoma

  • In this variant of ameloblastoma the neoplastic odontogenic epithelial cella proliferate in the form of “ contimuous anastomosing strands”. 
  • This patterm of neoplastic cell proliferation is also often called a “ fishnet like” pattern of arrangement.
  • The peripheral layer of cells tall columnar in nature and they often resemble the amelo-blasts.
  • Reverse polarization of the nucleu of these bordering cell is indistinct.
  • The cells situated at the center portion of the strands often resemble the stellate reticulum cells;while the cells located  berween the columnar cells and stellate reticulum cells often resemble the startum intermendium.
  • The intervening connective tissue stroma is usually thin , with minimum cellularity and often it show multiple areas of cystifications , which may be either large or small in size .


Follicular Ameloblastoma 


  • In follicular type , the neoplastic odontogenic epithelial cells proliferate in the from of multiple , discrete , follicles or islands within the fibrous connective tissue stroma.
  • Each follicle-like structure is bordered on the periphery by a single layer of tall columnar cells resembling ameloblasts. these cells have well-defined neclei situated away from the basement are called “reverse polarization” of the cell nuclei.
  • The cells located at the center of the follicles are loosely arranged and are triangular in shaps;these cells are widely seiarated from one another and they often resemble stellate reticulum cell (normally seen in the bell stage of odontogenesis)
  • While the cells located in berween the peripheral and the central group of cells appear as the stratum intermedium.
  • Occasionally a distinctive zone of hyalinization is seen surrounding the follicles.
  • Microcyst formation is often observed inside these follicles and the cysts sometimes may be large enough to occupy the entire inner part of the follicles.
  • Most of the follicular ameoloblastomas exhibit cyst formation particularty if the lesion is large.
  • The intervening connective  tissue strimas is delicate in nature and it consists chifly of collagen bundles,fibroblasts and blood vessels etc.
  • Extraosseous ameloblastoma consists of basaloid cells or they may even resemble the conventional intraosseous ameloblastomas.


Other Histological Types of Ameloblastoma

Besides the plexiform and the follicular types some other histological types of ameloblastomas can occur and they are as follows :


Acanthomatous type of ameloblastoma: It occurs in relation to follicular ameloblastoma and in this type the stellat reticulum-luke cells at the center of the follicles undergo squamous metaplasia. Sometimes the neoplastic epithelial cells can even produce “keratin pearls” whith the follicle the meoplastic cells may exhibit individual cell keratinization.


Granular cell type of ameloblastoma: In this type the cytoplasm of the stellate reticulum like cells and even the ameloblast like cells appear swollen and the cells are often densely packed with multiple, coarse,eosinophilic granules.Histologically this lesion often resembles “granular cell myoblastoma” and ultrastructural studies indicate that these geanules are either lysosomal elements or residual bodies.


Besal cell type of ameloblastoma: this lesion shows excessive proliferation of cuboidal shaped,bassaloid cells in narrow strands with the absence of stellate reticulum or other located cells The tumor often resembles basal cell carcinoma.


Cystic type of ameloblatoma: these lesions often exhibit multiple,small,microcyst formation inside the tumor.Some of the cysts are large in size


Desmoplastic type: In this type the epithelial islands or the strands are amall in size and the cells are ceboidal in shape and darkly stained.The cells of the epithelial components are widely separated by dense fibrous tissue. In this cells often penetrate into the surrounding trabacular bene.


Histogenesis of Ameloblastoma

Ameloblastoma develops from the odontogenic epithelial cells or their remnants but the exact cell of its origin is not very clearly known.According to different investigators, the possible cells or tissues from where ameloblastoma may arise are as follows.


  • Enamel organ of the developing tooth gern 
  • Cell rest of Serre (remnsnts of dental lamina)
  • Epithelial lining of the odontogenic cysts especially the dentigerous cyst.
  • The basal cell layer of the oral epithelium (rarely)
  • Cell rest of malassez.


Treatment

Surgical enucleation of the tumor and thorough curettage of the surrounding bone.Sometimes radical surgical approach may have to be adopted in case of repeared recurrences of the lesion Some tumors may cause distant matastasis.


0 comments:

Post a Comment