ameloblastic fibroma ( af ) is an extremely rare true mixed benign tumor that can occur either in the mandible or maxilla . it is frequently found in the posterior region of the mandible , often associated with an unerupted tooth . it usually occurs in the first two decades of life with a slight female predilection , causing delay in tooth eruption or altering the eruption sequence . small tumors are asymptomatic , while larger ones produce significant swelling of the jaws . on radiographs , smaller lesions are well circumscribed and unilocular with a sclerotic border , while larger ones are multilocular . histopathologically , af consists of odontogenic epithelium in the dental papilla - like background without dental hard tissue formation . similar lesions with hard tissue deposits are categorized as ameloblastic fibro - odontoma or odontoma depending on the degree of calcification . recently , there are few reports of this condition with high recurrence rates and malignant transformation . a 19-year - old female patient came to the department of oral medicine and radiology with a chief complaint of slowly progressive swelling on the right side of her lower posterior jaw . on intraoral examination , the right lower buccal vestibule was obliterated due to the expansion of the buccal cortical plate . the mucosa over the swelling was normal , except for slight blanching due to expansion of the buccal cortical plate . the lesion is seen extending from posterior aspect of first molar to the retromolar area , measuring 3 cm in size . on palpation , the swelling was slightly tender and no abnormality was detected in the adjacent teeth . panoramic radiograph showed a unilocular radiolucent area with well - defined borders , involving the posterior aspect of the right mandible . the lesion was measuring approximately 3.5 cm in size and was extending posteriorly from the distal aspect of the second molar to the retromolar area . microscopically , hematoxylin and eosin sections showed islands and strands of epithelial cells in a loose connective tissue stroma resembling primitive dental papilla [ figure 1 ] . the peripheral epithelial cells lining the islands and strands were low columnar , similar to the cells found in the peripheral layer of the follicle in ameloblastoma . the connective tissue resembled cellular fibroblastic tissue similar to the dental papilla in the developing tooth . hyaline - like tissue is also seen adjacent to the epithelial strands and islands [ figure 2 ] . it was interesting to note that both the epithelial islands and connective tissue stroma revealed high cellularity when compared with the conventional lesions of af . however , severe dysplastic features such as cellular and nuclear pleomorphism and increased number of abnormal mitotic figures were not observed . in this context , immunohistochemistry for ki-67 [ figure 3a ] proliferative marker along with proper positive [ figure 3b ] and negative [ figure 3c ] controls were performed . this had ruled out the diagnosis of a malignant tumor , confirming the diagnosis of af . photograph showing strands and islands of odontogenic epithelial cells in a loose connective tissue stroma resembling primitive dental papilla ( h and e  100 ) photograph showing the peripheral cells resembling ameloblasts with hyaline - like material surrounding the islands ( h and e  400 ) ( a ) photograph showing negative staining for ihc marker ki-67 antigen ( b ) photograph of positive control for ihc marker ki-67 antigen ( c ) photograph of negative control for ihc marker ki-67 antigen the histopathological finding of high cellularity in this lesion is uncommon as conventional afs show mild to moderate cellularity in a loose myxomatous connective tissue background . our case of af with high cellularity is unusual in the context of its histopathology .