shafer in 1983   introduced the term 
 ameloblastic carcinoma ( ac ) to describe ameloblastomas in which there had been 
 histological malignant transformation .
it is currently defined as a rare odontogenic malignancy that combines the 
 histological features of ameloblastoma with cytological atypia , even in the absence 
 of metastases .
although this lesion represents a separate entity , differentiating it 
 from ameloblastoma has been often challenging to pathologists .
recent study targets the different expression pattern of 
 immunohistochemical markers in order to differentiate a case of ac from 
 ameloblastoma .
a wide range of epithelial - associated factors are implicated in the relative 
 aggressive biological behaviour of the odontogenic epithelium while only a few 
 studies have investigated non - epithelial factors .
myofibroblasts 
 and cancer - associated fibroblasts are important components of the tumour stroma 
 .
in fact the presence of stromal 
 myofibroblasts has been linked to the biological behaviour of both benign and 
 malignant tumours . in a recent case study
, we attempted to differentiate ac from ameloblastoma on the 
 basis of difference in expression pattern of alpha smooth muscle actin 
 ( alpha - sma ) .
a 27 year old male patient presented to the department of oral and maxillofacial 
 surgery with a chief complaint of the pain and swelling over the left lower back 
 side of the face since last 4 months .
the swelling was insidious in onset and was 
 associated with moderate degree of pain .
the skin over the swelling was normal in 
 colour but there was slight increase in temperature .
intraoral examination revealed 
 expansion of the lingual cortical plate in the anterior aspect and buccal cortical 
 plate in the posterior region .
two ulcers were seen with respect to the swelling , 
 one on the anterior lingual aspect measuring about 12 x 8 mm and second one 
 measuring about 5 x 4 mm ( figure 1a , b ) .
intraoral view showing buccal ( a ) and lingual ( b ) cortical expansion and 
 overlying mucosal ulceration .
computed tomographic image of the mandible showed an ill - defined radiolucent mass 
 with respect to the left ramus / body area of size about 2 x 3 cm ( figure 2 ) .
the differential diagnosis included 
 aggressive odontogenic tumour , intraosseous squamous cell carcinoma , and metastatic 
 carcinoma .
incisional biopsy was performed and the findings were suggestive of ac . 
 as the patient did not give any history of previous surgery , so the primary variant 
 of ameloblastic carcinoma was considered .
patient underwent hemi - mandibulectomy 
 along with excision of the tumour mass under general anaesthesia , following which he 
 was suggested radiation therapy ( figure 
 3 ) . computed tomography image showing mandibular cortical plate expansion and 
 erosion of the bony plates . the surgically excised mandibular specimen showing the extent of the 
 lesion .
the excisional specimen underwent routine tissue processing and samples were used for 
 haematoxylin and eosin staining and immunohistochemical ( ihc ) staining for 
 alpha - sma .
sections of 3  thicknesses were cut and mounted on organo - silane coated 
 slides ( biogenex ) .
after dewaxing in xylene , sections were dehydrated in ethanol , 
 rinsed in distilled water , placed in 3% h2o2 for 10 min and rinsed in distilled 
 water for 15 min . for antigen retrieval procedure
, slides were placed in citrate 
 buffer solution , ph = 6 , in a microwave at 92 c for 10 min . after cooling at room 
 temperature for 20 min
, slides were exposed to primary alpha - sma mouse anti - human 
 antibody ( biogenex ) , dilution 1:100 , for 60 min at room temperature .
sections were rinsed in pbs for 10 min , 
 reacted with aec substrate - chromagen kit , rinsed in pbs for 2 min , counterstained in 
 harris hematoxylin ( nice chemicals ) , and covered with dpx mounting medium .
tissue sections of a specimen of follicular variant of solid multicystic 
 ameloblastoma were also examined for alpha - sma to determine whether these diagnostic 
 tests could be used to differentiate ac ( primary ) from ameloblastoma .
the hematoxylin and eosin stained sections of ac showed odontogenic epithelial 
 islands of highly irregular shape spread in a scanty fibrous connective tissue 
 stroma .
the central cells in few areas showed pleomorphism with an attempt of 
 malignant keratin pearl formation .
necrosis , vascular and neural invasion were not 
 observed ( figure 4 ) . based on the findings of cellular pleomorphism , presence of 
 mitotic figure and irregular shaped islands of odontogenic epithelial cells , a 
 diagnosis of ac was made .
haematoxylin and eosin stained section of ameloblastic carcinoma showing 
 cellular atypia ( original magnification x400 ) .
ihc stained slide of ac showed strong immunoreactivity to alpha - sma in the stroma 
 surrounding the tumour islands ( figure 5 ) . 

additional finding was that few cells within the tumour island also exhibited faint 
 positivity towards alpha - sma ( figure 6a , b ) . 
 while
in case of follicular ameloblastoma , alpha - sma positive cells were seen only 
 in the stroma and that too in reduced number .
positive cells in the wall of 
 endothelial vessels were taken as internal positive control ( figure 7 ) . increased expression of alpha smooth muscle actin in ameloblastic carcinoma 
 ( original magnification x100 ) .
expression of alpha smooth muscle actin ( indicated by arrows ) in the 
 epithelial islands of ameloblastic carcinoma : a = original magnification 
 x200 ; b = original magnification x400 .
expression of alpha smooth muscle actin in the stroma of follicular 
 ameloblastoma ( original magnification x200 ) .
two types of typical ameloblastoma must also be considered in the differential 
 diagnosis of ac .
first being the acanthomatous ameloblastoma which exhibits varying 
 degrees of squamous metaplasia and even keratinization of the stellate reticulum 
 portion of the tumour islands ; however , peripheral palisading is maintained and no 
 cytologic features of malignancy are found .
the other being kerato - ameloblastoma , 
 which is a rare variant of ameloblastoma that contains prominent keratinizing cysts 
 that may cause some alarm and distract the pathologist from the otherwise 
 ameloblastomatous features .
an additional consideration in the differential 
 diagnosis of ameloblastic carcinoma is squamous cell carcinoma arising in the lining 
 of odontogenic cyst .
histologically , this lesion tends to more closely resemble oral 
 squamous cell carcinoma than what we have described for ac .
however , it is of 
 interest that ac can apparently arise from a cystic lining .
posterior 
 portion of the mandible is the most common site of involve with maxillary 
 involvement being less frequent .
the lesion most commonly presents with swelling 
 with or without associated pain , rapid growth , trismus and dysphonia .
both , the 
 epithelium and the stroma , makes up an ecosystem in which there is a continuous 
 molecular cross - talk between the participating cells .
the appearance of 
 myofibroblasts in the adjoining stroma is secondary to the neoplastic changes in the 
 adjacent epithelium .
tgf1 and pdgf released by neoplastic cells , even at a 
 pro - invasive state , are responsible for emergence of myofibroblast .
tumour progression occurs within a microecosystem , where cancer cells and 
 myofibroblasts exchange proteinases and cytokines that promote growth directly 
 through stimulation of proliferation and survival , as well as invasion through local 
 proteolysis of the extracellular matrix and stimulation of motility .
studies on oral 
 squamous cell carcinoma demonstrated the increased stromal myofibroblasts as 
 assessed by alpha - sma immunoreactivity is associated with poor prognosis . in the present study we investigated the expression of alpha - sma in ac and compared 
 the findings to that of a case of follicular amelobalstoma .
increased expression of 
 alpha - sma positive cells was seen in the stroma of ac ( figure 5   and figure 6a , 
 b ) .
the expression of alpha - sma in the epithelial islands of ac was 
 minimal .
similar study was done by kamath et al .   and 
 bello et al . , and they also reported 
 increased expression of alpha - sma in the stroma of ac and few areas of epithelial 
 islands were also positive for alpha - sma .
they suggested the use of alpha - sma in 
 differentiating ac from ameloblastoma and expression of alpha - sma within the 
 epithelial islands is highly predictive of ac .
the role of myofibroblast in tumour progression is an important area of current 
 research and has emerged as a potential target for therapeutic intervention .
these 
 cells are recruited by the tumour cells and infiltrate the tumour microenvironment 
 to support tumour growth and progression by the secretion of growth factors , 
 extracellular matrix proteins , and by stimulating angiogenesis .
recent reviews have emphasized the advantages of therapeutic targeting of the 
 tumour - associated stroma as the stromal cells is presumably critical for the growth 
 of nearby neoplastic cells and these are stable genetically in contrast to carcinoma 
 cells , which accumulate adaptive mutations during the course of therapy in order to 
 acquire drug resistance . at present , there are relatively few studies in support of the expression of 
 alpha - sma in odontogenic carcinomas to correlate it with the diagnosis and prognosis 
 of these lesions .
study involving larger sample size and survival analysis is needed 
 to validate this conclusion .
pathologist still find it 
 difficult to differentiate a case of ameloblastoma from ameloblastic carcinoma . 

immunohistochemical expression of alpha smooth muscle actin may help in establishing 
 an early diagnosis and chemotherapeutic agents against stromal myofibroblasts can be 
 used as an adjunct to the surgery in planning the treatment for these locally 
 aggressive and infiltrating lesions .
 abstractbackgroundthe aim of the present article is to report a case of ameloblastic carcinoma 
 and use a marker alpha smooth muscle actin as a tool to differentiate cases 
 of ameloblastic carcinoma from that of ameloblastoma.methodscase study reporting a case of ameloblastic carcinoma ( ac ) with expression of 
 alpha smooth muscle actin ( alpha - sma ) as a marker for emergence of stromal 
 myofibroblasts . 
 the expression of myofibroblasts was also compared with that 
 of ameloblastoma.resultsdifference between the two lesions in the pattern of expression of alpha 
 smooth muscle actin was also observed . 
 there was increase in the number of 
 myofibroblasts in the stroma of ac while in ameloblastoma , it was 
 comparatively less . 
 secondly , few areas of the carcinomatous ameloblastic 
 island also exhibited a mild positivity towards alpha smooth muscle 
 actin.conclusionsincrease in number of stromal myofibroblast may be taken as a predictor for 
 carcinomatous transformation . 
 further studies with greater sample size can 
 validate the use of alpha - sma as a marker to differentiate ameloblastic 
 carcinoma from ameloblastoma . 
INTRODUCTION
CASE DESCRIPTION AND RESULTS
DISCUSSION
CONCLUSIONS
ACKNOWLEDGMENTS AND DISCLOSURE STATEMENTS