Keratoameloblastoma: a tumor sui generis or a chimera?

An Unusual Gingival (Peripheral) Tumor with Features of Keratoameloblastoma with Cytologic Atypia or Possible Malignant Transformation Exhibiting ARID1A Mutation

BACKGROUND

Keratoameloblastoma is a poorly characterized and rarely reported odontogenic neoplasm that can exhibit overlapping histopathologic features with conventional ameloblastoma and keratocystic odontogenic tumor (KCOT), with an ambiguous relationship to the so-called solid KCOT.

METHODS

A peripheral maxillary tumor causing bone saucerization in a 54-year-old male is described and investigated with immunohistochemistry and Next-Generation Sequencing (NGS).

RESULTS

Microscopically, the tumor comprised of a predominantly plexiform proliferation of odontogenic epithelium with central keratinization and evidence of surface origin. Peripheral cells exhibited nuclear palisading with variable reverse polarization, while stellate reticulum-like areas were observed internally. A few follicles and a few foci in the lining of cystic spaces revealed increased cellularity with cells exhibiting small but conspicuous nucleoli, focal nuclear hyperchromatism, and a few mitoses mostly seen in the peripheral outer cell layer. Nuclear staining for ki-67 was increased in those areas when compared with the other cystic, follicular, and plexiform areas. These features were interpreted as cytologic atypia suggesting also the possibility of a malignant process. Immunohistochemically, the tumor was positive for CK19 and negative for BRAF VE1, calretinin, and CD56. Ber-Ep4 was only focally positive. By sequencing, an ARID1A c.6527_6538delAG frameshift mutation (VAF: 5.8%), classified as likely oncogenic, and an FBXW7 c.1627 A > G missense mutation (VAF: 8.0%), classified as a variant of uncertain significance, were detected. Two mutations, probably germline (VAF ~ 50%), were recorded for RNF43 and FBXW7. No pathogenic variants were identified in PTCH1, BRAF, NRAS, HRAS, KRAS, FGFR2, or SMO genes.

CONCLUSION

The significance of an ARID1A variant in keratoameloblastoma is uncertain since this variant has not been reported in ameloblastoma or KCOT, to date. Alternatively, it may characterize malignant transformation in the present case since ARID1A mutations have been encountered in various cancers. Sequencing of additional cases is necessary to determine whether this may represent a recurrent genomic event.

Keratoameloblastoma: A Report of Seven New Cases and Review of Literature

BACKGROUND

Keratoameloblastoma (KA) is an uncommon and controversial variant of ameloblastoma exhibiting central keratinisation. Due to their rarity, there is limited information in the literature on their clinical, radiologic and histologic features. This study adds seven additional cases of KA to the literature, and reviews the current published literature on this rare entity.

METHODS

KAs were retrospectively reviewed over a 20-year period from three Oral and Maxillofacial Pathology Laboratories. Included cases were examined and the diagnosis confirmed under conventional microscopy. Immunohistochemistry with the use of a monoclonal antibody against calretinin was performed on included cases. The clinical, radiologic and histologic features of the seven new cases of KA were analysed and compared to existing cases in the literature.

RESULTS

KAs presented at a mean age of 40 years with a nearly equal gender distribution and a mandibular predilection (65%). The majority (92%) of cases presented with localised swelling with associated pain in 32% of cases. Mixed density or internal calcifications were noted in 40% of cases. All tumours presented with bony expansion, with cortical destruction noted in 62% of cases. Histologically, all tumours consisted of solid and cystic follicles with surface parakeratinisation and lamellated accumulations of central keratin. In areas the cystic follicles had an epithelial lining suggestive of an OKC. There were focal luminal areas of loosely arranged polygonal cells reminiscent of the stellate reticulum. The basal cells consisted of columnar cells with evidence of palisading and prominent subnuclear vacuolisation. Of the cases treated via tumour resection, 27% presented with tumour recurrence.

CONCLUSION

This case series reports seven additional cases of KA, taking the total to 26 reported cases. The identification of subtle histologic features, including focal stellate reticulum-like central areas, subnuclear vacuolisation and lamellated-type central keratinisation, are key in diagnosing KA. The radiologic features will often indicate signs of aggressiveness such as cortical destruction, differentiating KA from OKC. All cases were completely negative for calretinin IHC, limiting its use in distinguishing KA from OKC. Further large series are needed to expand the current understanding of this rare variant of ameloblastoma.

Should the solid variant of odontogenic keratocyst and keratoameloblastoma be classified as the same entity? A clinicopathological analysis of nine cases and a review of the literature

The solid variant of odontogenic keratocyst (SOKC) is an extremely rare odontogenic lesion, which remains poorly defined even in the 2017 World Health Organization odontogenic tumour classification. It is difficult to distinguish between SOKC and so called keratoameloblastoma (KAB), both rare lesions that have similarities in clinical, histological and biological characteristics. Here, we report clinicopathological data and results of molecular analysis of nine cases with a literature review. First, they were compared to previously reported cases of SOKC and/or KAB, and many overlaps were found in clinical and pathological characteristics. Second, we performed PCR analysis for BRAF V600E mutation. Although ameloblastoma-like epithelia were often encountered, none exhibited BRAF V600E mutation, which has been reported to occur frequently in ameloblastomas but not in odontogenic keratocysts (OKCs). One of two cases of SOKC in the present series from which fresh frozen tissue specimens were available was found to harbour PTCH1 mutations, indicating that these were more likely to be a subtype of OKC. Moreover, we also examined the differences between SOKC and primary intraosseous carcinoma (PIOC) with regard to the expression of cytokeratins (pan-CK, CK5/6, CK7, CK8/18, CK10, CK14 and CK19), p53 and Ki-67. The proportions of p53-and Ki-67-positive cells were significantly higher in PIOC than in SOKC. These findings suggest that immunostaining for p53 and Ki-67 would be useful to differentiate between SOKC and PIOC. We also conducted a review of SOKC and KAB cases reported in the English language literature.

Papilliferous keratoameloblastoma - A rare entity: A case report with a review of literature

Ameloblastoma is the most common odontogenic tumor which presents with a variety of histopathological patterns. Among all, papilliferous keratoameloblastoma (PKA) is a very rare type which is characterized by multiple epithelial cysts of varying size, which are lined by non-keratinized papilliferous epithelium which is filled with necrotic desquamated epithelial cells. In this study, we reported PKA with characteristic ameloblastic features in a 65-year-old male patient who presented with a swelling in the right mandibular body region. This is the seventh case of PKA to be reported in the English literature till date. Present case showed multicystic areas in incision biopsy which lead to misdiagnosis as calcifying odontogenic cyst with adenomatoid odontogenic tumor, but in excision biopsy which turned out to be papilliferous keratoameloblastoma, further in this paper we had discussed all the areas which lead to misdiagnosis of calcifying odontogenic cyst with adenomatoid odontogenic tumor. In outlook, more cases will put an insight to the behavioral aspects of this rare histological type of ameloblastoma.

Peripheral keratoameloblastoma: A novel case report

Keratoameloblastoma is an exceptionally rare subtype of ameloblastoma that has been reported <20 times previously in the literature. All present as intraosseous lesions. We report an unusual case of keratoameloblastoma localized in the palate without involving palatal bone, thus presenting as a peripheral lesion. To the best knowledge of the authors, no case of peripheral keratoameloblastoma has been reported in the English literature till now, probably rendering this case to be the first one. Therefore, the purpose of this article is to present a rare and the first case of peripheral keratoameloblastoma with histopathological features of this tumor.

Papilliferous Keratoameloblastoma: A Rare Case Report

Ameloblastoma is true odontogenic tumor of epithelial origin, which is described as locally aggressive with varying chances of recurrence. It is believed to derive from enamel organ, remnants of dental lamina, lining of odontogenic cysts, or basal cells of oral epithelium. Radiologically, it may present as unilocular or multilocular radiolucency commonly. Although conventional ameloblastoma presents typical histological features as described by Vickers and Gorlin, few unusual variants have been reported with different histological patterns. However, the clinical and biological behavior of these lesser known variants has not been established yet due to the scarcity of cases reported. Here, we report an extremely rare case of papilliferous ameloblastoma in a young male patient with 2-year follow-up and presenting with unusual histological presentation than conventional ameloblastoma.

Keratoameloblastoma of the mandible

INTRODUCTION

Keratoameloblastoma is an extremely rare odontogenic tumor, as only 18 cases have been reported in the literature.

CASE REPORT

The authors report a case of keratoameloblastoma in a 32-year-old woman and review the literature concerning the clinical features, radiological appearance, histopathological findings and treatment options.

DISCUSSION

Keratoameloblastoma is a rare tumor observed more frequently in males (sex ratio: 3:1) characterized by extensive keratin production in odontogenic islets and fibrous stroma.

Papilliferous Keratoameloblastoma of the Mandible - A Rare Case Report

Ameloblastomas are common odontogenic tumours that are benign and locally aggressive. Histopathologically, the tumor exhibits significant diversity with common and rare variants. Here, we report an unusual variant of a common odontogenic tumour in the mandibular posterior region on the right side in a 44-year old male patient. This is the sixth case of Papilliferous Keratoameloblastoma (PKA) to be reported in the English literature till date. More case reports are vital to determine the clinical, radiological, histopathological and behavioural aspects of this extremely rare histological type of ameloblastoma. This tumour awaits re-inclusion as a distinct entity in the future classifications of the WHO Classification of head and neck tumours upon further case accrual.

Odontogenic Cysts and Tumors

This article presents various odontogenic cysts and tumors, including periapical cysts, dentigerous cysts, odontogenic keratocysts, orthokeratinized odontogenic cysts, lateral periodontal cysts, glandular odontogenic cysts, ameloblastomas, clear cell odontogenic carcinomas, adenomatoid odontogenic tumors, calcifying epithelial odontogenic tumors, squamous odontogenic tumors, ameloblastic fibromas, ameloblastic fibro-odontomas, odontomas, calcifying cystic odontogenic tumors, and odontogenic myxomas. The authors provide an overview of these cysts and tumors, with microsopic features, gross features, differential diagnosis, prognosis, and potential diagnostic pitfalls.

Keratoameloblastoma or Kerato-odontoameloblastoma: report of its soft tissue recurrence with literature review

Keratoameloblastoma (KA) is a rare histological variant of the ameloblastoma with extensive keratin production within the odontogenic islands as well as in the fibrous stroma. Pindborg first reported it in 1970, since then only 18 cases have been reported in the literature. We report a soft tissue recurrence of KA, involving right posterior region of the lower jaw in a 27-year-old female.

Keratoameloblastoma a rare entity: a case report

Ameloblastoma is the second most common odontogenic tumour of oral cavity; which has several different histological variants such as follicular, plexiform, acanthomatous, granular cell, desmoplastic, basal cell, clear cell, hemangiomatous, mucous cell differentiation and keratoameloblastoma. It is common in posterior mandible and has high male predilection in the ratio of 3:1. This report presents a case of keratoameloblastoma in 65-year-old female patient in the anterior mandible region with literature review on clinical features, histopathological findings, radiological appearance and treatment options.

NCAM (CD56) expression in keratin-producing odontogenic cysts: aberrant expression in KCOT

Objective

To investigate immunohistochemically the expression of neural cell adhesion molecule (NCAM), which has been identified as a signaling receptor with frequent reactivity in ameloblastomas (AB), in a series of keratin-producing odontogenic cysts (KPOCs).

Material and methods

Immunohistochemical expression of NCAM, using a monoclonal antibody, was determined in a series of 58 KPOCs comprising 12 orthokeratinized odontogenic cysts (OOCs) and 46 keratocystic odontogenic tumors (KCOTs), corresponding to 40 non-syndromic KCOT (NS-KCOTs) and 6 syndromic KCOT (S-KCOTs), associated with nevic basocellular syndrome (NBCS).

Results

NCAM expression was negative in all OOCs, but 36.45% of KCOTs exhibited focal and heterogeneous expression at the basal cell level, as well as in basal budding areas and the basal cells of daughter cysts. The latter two locations were especially applicable to S-KCOTs, with focal NCAM reactivity occurring in 66.66% of cases.

Conclusions

Aberrant NCAM expression, in KCOTs but especially in S-KCOTs, together with its immunomorphological location, suggests that this adhesion molecule and signaling receptor plays a role in the pathogenesis of KCOTs, with a probable impact on lesional recurrence.

Electronic supplementary material

The online version of this article (doi:10.1186/s13005-015-0060-2) contains supplementary material, which is available to authorized users.

Papilliferous keratoameloblastoma: an extremely rare case report

Odontogenic tumors develop in the jaw bones from the odontogenic tissue-oral epithelium in tooth germ, enamel organ, dental papilla, reduced enamel epithelium, remnants of Hertwig's root sheath or dental lamina, and so forth. Hence, a bewildering variety of tumors are encountered in the maxilla and mandible. Ameloblastoma is the second most common odontogenic neoplasm after odontomes, and it has numerous clinical and histologic variants. We report a very rare histologic variant: the papilliferous keratoameloblastoma which is the fifth reported case in the English literature.

Solid variant of keratocystic odontogenic tumor with ameloblastomatous transformation: a case report and review of the literature

The solid variant of keratocystic odontogenic tumor is an extremely rare tumor. Its clinical and pathologic features remain poorly defined, even in the 2005 World Health Organization odontogenic tumor classification. We report an unusual lesion in a 38-year-old female Chinese patient. The lesion demonstrated the solid or multiple cystic architecture of a keratocystic odontogenic tumor, but also exhibited ameloblastomalike lining epithelium in some areas. The complex histopathology made a pathologic diagnosis difficult. Finally, the lesion was diagnosed as solid variant of keratocystic odontogenic tumor with ameloblastomatous transformation. We present the clinical and pathologic details of the case, and review the relevant literature.

Keratoameloblastoma of the mandible

Keratoameloblastoma is a very rare ameloblastoma variant defined by extensive squamous metaplasia and keratinization. There are 13 previously reported cases in the literature, with a male predilection of 3:1. A 38-year-old male presented with a painless mandibular swelling which had been progressively increasing in size for 18 months. The incisional biopsy was misdiagnosed as basaloid squamous carcinoma. Owing to financial constraints, the patient had mandibular resection a decade after first noticing the growth, during which the clinical course was essentially benign, thus casting doubt on the initial diagnosis. The final histological diagnosis for both the incisional and resection biopsy specimens was keratoameloblastoma.

Tubulopapillary hidradenoma-like tumor of the mandible

Tubulopapillary hidradenomas are uncommon benign tumors of the dermis, most commonly occurring in the skin of the head or of the extremities. Complete excision is generally curative and recurrences are rare. The authors describe an unusual case of an intraosseous tubulopapillary hidradenoma of the mandible that recurred 1 year after initial curettage and required en-bloc resection.

Diagnostically challenging epithelial odontogenic tumors: a selective review of 7 jawbone lesions

Considerable variation in the clinicopathologic presentation of epithelial odontogenic tumors can sometimes be confusing and increase the chance of misdiagnosis. Seven diagnostically challenging jawbone lesions are described. There were 2 cases of mistaken identity in our ameloblastoma file. One unicystic type, initially diagnosed and treated as a lateral periodontal cyst, showed destructive recurrence 6 years postoperatively. The other globulomaxillary lesion was managed under the erroneous diagnosis of adenomatoid odontogenic tumor and recurred 4 times over an 11-year period. This tumor was found in retrospect to be consistent with an adenoid ameloblastoma with dentinoid. The diagnosis of cystic squamous odontogenic tumor (SOT) occurring as a radicular lesion of an impacted lower third molar was one of exclusion. Of two unsuspected keratocystic odontogenic tumors, one depicted deceptive features of pericoronitis, while the other case has long been in our files with the diagnosis of globulomaxillary SOT. Two cases of primary intraosseous squamous cell carcinoma appeared benign clinically and exhibited unexpected findings; an impacted third molar began to erupt in association with the growth of carcinoma and another periradicular carcinoma showed dentinoid formation. Cases selectively reviewed in this article present challenging problems which require clinical and radiographic correlation to avoid potential diagnostic pitfalls.