histomorphology: A case study

A 6 year old female Spitz dog was admitted to Teaching Veterinary Hospital at Chittagong Veterinary and Animal Sciences University with the history of inappetance and asymmetric lower jaw. Oral inspection revealed a pair of pale enlarged lobulated mass around the third molar tooth of the left mandible. The dog was clinically diagnosed with epulis and successfully cured by surgical excision. Histopathological section of the excised masses revealed characteristic features of acanthomatous ameloblastoma with some atypical lesions. Multifocal areas of ameloblastic islands were found in the dense sheet of proliferating epithelial layer protruding towards the sub epithelial connective tissue stroma. These islands were characterized with irregular epithelial stratification at the basal layer. Besides, presence of ghost cells was the unusual findings for such case. Prominent intercellular bridging and nuclear polymorphism in odontogenic cells were other decisive characters of the lesion. Based on the histomorphological appearance, the gingival tumor was designated as canine acanthomatous ameloblastoma (CAA) with atypical histomorphology.


Case report
Canine acanthomatous ameloblastoma (CAA); A six (6) years old female spitz dog of 10 kg body previously known as acanthomatous epulis is an weight was admitted to the SA Quadery Teaching aggressive tumor of the jaw characterized by the Veterinary Hospital (SAQTVH), Chittagong Veterinary presence of irregular verrucous masses adjacent to the and Animal Sciences University, Bangladesh.The dog tooth [1][2].Alike other types of epulis they are had a clinical history of excessive salivation, bad breath, clinically indistinguishable exophytic growth on inappetence and asymmetric lower jaw for several gingiva.Although most clinical cases of epulides are days.Close inspection of the oral cavity revealed a firm not characterized histologically; some reports of growth (gingival mass) measuring 2.0 × 0.4×0.6 cm acanthomatous epulis have been published [3][4].The diameter protruding from the left mandibular gingiva word "ameloblastoma" relates to the enamel producing around third molar tooth.The growth was paired, pale odontogenic epithelial cells, and "acanthomatous" pink in color, smooth surfaced and attached with the refers to the spiny shape of epithelial cells within these gum by a stalk-like structure, pressing and misaligning tumors [5].These tumors show diverse histomorphic the adjacent teeth (fig.1).The dog was premedicated features which are easily confusing with other and subjected to general anesthesia for surgical neoplasms; often mimicking with variants of intervention.Clean surgical excision was made ameloblastomas observed in humans.Typically, the following standard procedure which involved excision microscopic features of CAAs are characterized by of 1cm healthy tissue around the gingival mass (fig.2).islands and cords of proliferating odontogenic cells in Post operative care and medication was properly gingival mucosa bordered by a row of characteristic maintained and follow up observation was conducted ameloblastic cells.But these histological features may in following three months for any evidence of not be consistent in every case and therefore may create recurrence.The excised masses were fixed in 10% difficulty in diagnosis.They are histologically benign neutral buffer formalin and processed accordingly for tumor but often show local invasiveness which may histopathology at the Department of Pathology and attributes in recurrences following surgical excision Parasitology.Paraffin embedded tissue sections of 5µ [6].The present report has concentrated on the thickness was stained with Hematoxyline and Eosin (H histomorphological features of a non recurring CAA in and E) and examined under low and high power a Spitz dog housed in Chittagong city, Bangladesh.To microscope.The gingival lesion completely healed the best of our knowledge this is the first report of its following surgery and did not recur in three month kind in Bangladesh.
observation period.
The microscopic section of the gingival mass was overgrowth where numerous polyhedral cells invaded visualized as thickening (acanthosis) of the stratum the capillary walls (fig.6).spinosum and anastomosing reti-ridges in the Discussion hyperplastic epithelial layer protruding deep into the Even though, epulides are considered as common connective tissue stroma (fig.3).Distinct sheets and oral neoplasms in dogs, the term epulis does not always cords were formed by the proliferation of squamous represent tumors; rather simply refers to localized type epithelial cells (fig.4).Multifocal islands formed gingival enlargement of either non-neoplastic reactive by ameloblastic cells were visible within the epithelial or neoplastic origin [7][8][9].Reactive epulides such as overgrowth whereas sub epithelial connective tissue fibrous hyperplasia, pyogenic granuloma, peripheral stroma comprised of stellate shaped cells with oval to giant cell granuloma, reactive exostosis have been elongated nuclei (fig.4).The epithelial islands were reported in many species.On the contrary, fibroamabordered by multiple layers of columnar to polyhedral tous, ossifying and acanthomatous ameloblastoma are type cells which are palisaded and showed reverse the examples of neoplastic epulis of canines [10][11].nuclear polarity; i.e. the nuclei of the cells were in the Recently clinical research has been focused on specific opposite end of the basal layer (fig.5).

Distinct diagnosis of such tumors based on histomorphological intercellular bridging between the odontogenic characters [12]. epithelial cells was visible as en evidence of extensive
In the present study, although most of the gross cellular proliferation (fig.6).At the center of the and microscopic features of the tumorous growth came cellular mass some cells were visible with nuclear in agreement with the existing references [12] of vacuolation leaving a pale eosinophilic granular cytocanine acanthomatous ameloblastoma (CAA), some plasm and remnants of nuclear membrane, therefore histomorphic traits seem atypical.Classically CAA is appearing as "ghost cells" (fig.6).High degree of an aggressive tumor of the canine jaw where proliferavasculariation was noticeable within the epithelial      ting ameloblastic cells invades the deep sub mucosa of Histochemical study of a classical ameloblastoma the gingiva [12].The microscopic section of the with similar microscopic lesion have demonstrated gingival mass studied here demonstrates a thickened strong positive reaction to epithelial marker (cytokeratin) epithelial layer forming distinct cord like projections.
compared to connective tissue marker (vimentin) and Similar histomorphic features have been discussed conclusively proved that such proliferation was epithepreviously by many authors [13][14].
lial origin [23].Therefore, based on histological In this case, instead of typical single layer tall attributes, the gingival lesions in the above studied case columnar cells (amelobalsts), unusual multilayered can be designated as canine acanthomatous amelocells were found in the border of ameloblastic islands.blastoma (CAA) and the unusual features can be The nuclei of these columnar cells remain in opposite described as atypical histomorphology for the time direction of basement membrane; a characteristic being.feature referred as reverse nuclear polarity [15][16].The Postoperative observation over three month multilayered basal cells observed in this case might be period showed no evidence of recurrence and thus expressed as "irregular epithelial stratification".Such indicates favorable outcome.Recurrences usually distinction in epithelial layer resembles to some reports happen due to deeper invasion of neoplastic tissue in of ameloblastomas [17].Intercellular bridging in the bone or following marginal surgical excision [23].proliferating ameloblasts with nuclear polymorphism, These recurrent tumors are more aggressive and higher nuclear-cytoplasmic ratio and hyper chromatic anaplastic and their biological behaviors are similar to nuclei were other microscopic features in this case.
that of squamous cell carcinoma [24].Hence wider These lesions are quite similar to the finding of surgical excision (with bone removal) is considered the previous researchers [17].
fastest and most curative treatment for acanthomatous At higher magnification, the center of the epithe-ameloblastoma [24].Radiation therapy has also been lial mass revealed some enlarged, ovoid to ellipsoid reported effective in treating CAAs.Intralesional (IL) cells with nuclear vacuolation and pale eosinophilic chemotherapy is another option for treating and granular cytoplasm.These peculiar cells are consid-bleomycin has been proved as an effective IL chemoered as "ghost cells" which is unlikely for CAAs but therapeutic agent for such case [25].common in dentinogenic ghost cell tumors (DGCT) of

Conclusion human [18]. Ghost cells are thought to be transformed
The case described above is the first of its kind in odontogenic epithelial cells, but the mechanism of its Bangladesh, besides it might contribute to a paradigm transformation is yet unknown [19].Sometimes ghost shift of knowledge in describing such tumors in dogs.cells contain nuclear remnants in various stages of Further study is required on histochemical basis to degeneration which was also seen in this case.Ultra explore any newer variation among CAAs.Alternative structurally these ghost cells carry fine calcium treatment procedures like chemotherapy or irradiation granules which originate from dystrophic calcification should be explored for reducing health hazard of [20].
surgery with actively considering efficacy and cost The histological features of CAAs can be easily requirements.confused with fibromatous epulis of periodontal ligament origin (FEPL); but FEPLs can be distingui-

Figure- 1 .
Figure-1.Pre-operative appearance of the gingival mass; pale, blunt and multilobulated oral mass around the lower 3rd molar tooth of the mandible.

Figure- 2 .
Figure-2.Post operative appearance of the jaw after clean surgical excision of the mass.

Figure- 4 .
Figure-4.Sheets of ameloblastic epithelial cells forming a cord like structure (light arrow).Ameloblastomatous islands formed within the epithelial overgrowth (blue arrowhead).Sub epithelial connective tissue (s) comprised of stellate shaped cells with oval to elongated nuclei [Hemataoxylin and Eosin, × 500].

Figure- 5 .
Figure-5.Acanthomatous ameloblastoma with evident atypical features showing Irregular epithelial stratification (S) at the periphery of ameloblastomatous islands.Reverse nuclear polarity of the columnar cells visible at the border of connective tissue stroma (arrowhead) [Hemataoxylin and Eosin, × 3000].