Case report
Year : 2025 Month : April Volume : 14 Issue : 2 Page : PC05 - PC07 Full Version

Adenoid Ameloblastoma with Dentinoid: A Case Report
Jayapriya Gangadharan
1. Assistant Professor, Department of Pathology, Government Medical College, Ernakulam, Kerala, India.
 
Correspondence Address :
Dr. Jayapriya Gangadharan,
Assistant Professor, Department of Pathology, Government Medical College, Ernakulam-683104, Kerala, India.
E-mail: ampriya1983@gmail.com
 
ABSTRACT
: Odontogenic tumours are a heterogenous group of lesions that range from hamartomas to benign and malignant neoplasms. 2022 World Health Organisation (WHO) classification classifies benign odontogenic tumours based on their origin from epithelial, ectomesenchymal, or mixed components of odontogenic apparatus. However, there have been isolated case reports and case series of hybrid odontogenic lesions having combined histopathologic features of two or more recognised odontogenic cysts or tumours, affecting the same primary site. These group of lesions are a challenge to pathologists and surgeons, as their histogenesis and clinical behaviour is poorly understood. Adenoid Ameloblastoma with Dentinoid (AAD) is one such variant showing features of both ameloblastoma and Adenomatoid Odontogenic Tumour (AOT) and a high propensity for recurrence. Hereby, the authors present a case of a 36-year-old male who presented with a slow growing right-sided mandibular swelling of five months’ duration. Radiologically, there was a well-defined unilocular radiolucent lesion with smooth margins related to 1st and 2nd premolars and 1st molar. Magnetic Resonance Imaging (MRI) revealed a mixed density mostly cystic lesion involving right mandible. Histologically {Haematoxylin and Eosin (H&E)} the tumour showed hybrid features of ameloblatoma and Adenomatoid Odontogenic Tumour (AOT), with dentinoid formation. Authors report present case owing to the rarity of the lesion, as fewer than 50 cases have been reported in the literature to date.
Keywords : Adenomatoid odontogenic tumour, Histogenesis, Hybrid odontogenic tumour, Lymphadenopathy
DOI and Others : DOI: 10.7860/NJLM/2025/76854.2913 Date of Submission: Nov 16, 2024 Date of Peer Review: Dec 10, 2024 Date of Acceptance: Feb 18, 2025 Date of Publishing: Apr 01, 2025 AUTHOR DECLARATION: • Financial or Other Competing Interests: None • Was informed consent obtained from the subjects involved in the study? Yes • For any images presented appropriate consent has been obtained from the subjects. Yes PLAGIARISM CHECKING METHODS: • Plagiarism X-checker: Nov 18, 2024 • Manual Googling: Jan 31, 2025 • iThenticate Software: Feb 15, 2025 (3%) ETYMOLOGY: Author Origin EMENDATIONS: 7
 
Case Report
A 36-year-old male presented with history of pain and swelling of the right lower jaw since five months, with recent increase in size. On examination, there was a soft to firm swelling of right mandible extending from 1st premolar to the second molar, with associated teeth, measuring 3×4 cm. Overlying mucosa and skin were normal and there was no significant lymphadenopathy. An Orthopantomogram (OPG) showed a well-defined unilocular radioluscent lesion in the right mandible, related to 1st and 2nd premolars and 1st molar (Table/Fig 1). An MRI revealed a mixed-density mostly cystic lesion along right side of mandible. Clinical differential diagnosis were an inflammatory or developmental odontogenic cyst, or unilocular ameloblastoma; an incisional biopsy done. Patient did not have any significant past medical or drug history. Incision biopsy showed a cyst wall with a neoplasm composed of ameloblastic areas and areas resembling AOT and a diagnosis of Ameloblastoma with adenoid differentiation was given. The patient underwent wide excision with corticotomy and angle reconstruction. Grossly, it was an irregular ruptured cystic mass with attached portion of bone. The cyst wall was shaggy, grey-brown, with whitish areas.

The tumour was unicystic with thick fibrous capsule, with mural and intraluminal components. The ameloblastic component was predominantly found as a mural component arranged in plexiform and follicular pattern with peripheral ameloblast resembling epithelium showing reverse polarity (Table/Fig 2),(Table/Fig 3). The central cells of the follicles were compactly arranged, ovoid to spindle-shaped, resembling stellate reticulum seen streaming between duct-like spaces lined by cuboidal cells containing eosinophilic material. The luminal component showed nodules, sheets and plexiform arrangement of basoloid, short, spindly, or ovoid cells with prominent gland-like and cystic spaces. Also noted was an abundant extracellular eosinophilic matrix consistent with dentinoid (Table/Fig 4). Areas of squamous metaplasia, cellular whorls, ghost cells and clear cells were seen in the central component of the ameloblastic follicles and the adenoid areas (Table/Fig 5),(Table/Fig 6),(Table/Fig 7). A calcified mass of dentin was also present, periphery of the tumour showed rim of new bone formation (Table/Fig 8).

Cytokeratin (CK) 19 was diffusely positive in the tumour cells, with greater intensity in stellate reticulum, cellular whorls and areas of squamous metaplasia (Table/Fig 9). CK7 was faintly positive in the stellate reticulum cells of the ameloblastic follicles, while calretinin was uniformly negative in tumour cells. Ki67 was 2%.

The patient was under regular follow-up and did not show any signs of recurrence 12 months following surgery.
 
 
Results
The AAD is an odontogenic tumour with histopathologic features of both AOT and ameloblastoma, associated with extracellular dentinoid meterial. The first description of this entity was provided by Armed Forces Institute of Pathology (AFIP) in 1994.

Several authors earlier had noted focal adenoid features associated with ameloblastoma and hard tissue formation; but they preferred to call it by other names, like dentinoameloblastoma, ameloblastoma arising in calcifying odontogenic cyst and adenoameloblastic odontoma. Sathyanarayana VK et al., and Jivan V, had described histologically similar cases as AOT originating in unicystic ameloblastoma (1),(2). Presence of both follicular and plexiform pattern in ameloblastoma component has been previously described by Yamasaki M et al., Loyola AM et al., Khalele BA and Al-Shiaty RA [3-5]. The present case also showed presence of both follicular and plexiform pattern in the mural ameloblastic component of the tumour.

Squamous metaplasia within central reticulum cells is frequently found in ameloblastoma and is termed acanthomatous ameloblastoma. Acanthomatous change was similarly noted in central reticulum cells within ameloblastic follicles in present case. Squamous metaplasia was observed in all eight cases reported by Adorno-Farias D et al., (6).

Presence of clear cells in tumour population in AAD has been described by various other authors (4),(7). Focal clear cell change is due to accumulation of glycogen or lack of organelles, which could be explained by the origin of odontogenic tumours from dental lamina, which has a clear cell component. Ghost cells are pale eosinophilic, balloon-shaped epithelial cells that have lost their nuclei, leaving only a faint outline. They are proposed to result from abnormal keratinisation or squamous metaplasia, with subsequent calcification due to ischemia, coagulation necrosis, or due to an apoptotic process. They have been decribed in four cases of AAD. Ghost cells and clear cells were seen in the central component of the ameloblastic follicles and the adenoid areas in present case as previously described in the literature.

Extensive dentinoid formation, as seen in present case, is a feature described in several odontogenic tumours. Jayasooriya PR et al., proposed that the identification of dentinoid is one of the diagnostic features of this tumour (8). However, Adorno-Farias D et al., considers the finding non essential for diagnosis, as it was found in only two out of eight cases in their study (6). They are considered to be formed by a metaplastic process (9) or due to inductive effect of epithelial-mesenchymal interaction.

Peripheral rim of new bone formation has not been previously reported in any case studies of AAD. However, present case demonstrated the formation of a rim of new bone at the periphery of the tumour, which is unlike previous reported cases.

Regarding Immunohistochemistry (IHC), CK19 was diffusely positive in the tumour population, with greater intensity observed in stellate reticulum-resembling cells and in the epithelial whorls. This varying intensity of CK19 staining has been reported by Martínez-Martínez M et al., in ameloblastomas (10). Positive CK19 indicates an odontogenic epithelial origin, as it can be seen in various odontogenic epithelial tumours (11). CK7 was found to be taken up weakly by the stellate reticulum cells in the follicular areas. Loyola AM et al., had similarly described similar weak staining in the central cells in his study (4). All the eight cases reported by Adorno-Farias D et al., were negative for CK7 (6). Literature regarding expression of calretinin has been conflicting till date. Jivan V et al., Yamazaki M et al., Khalele BA and Al-Shiaty RA has reported positive expression in ameloblastomatous component in AAD (2),(3),(5). Bilodeau EA and Seethala R in her case series reported absent expression of calretinin in their case series (12). However, none of these IHC markers are specific for adenoid ameloblastoma and diagnosis primarily relies on morphology.
 
 
Conclusion
The AAD is a rare tumour that has been described by various authors in isolated case reports and case series. The 2022 WHO classification of odontogenic tumours has officially acknowledged adenoid ameloblastoma as a distinct benign epithelial odontogenic tumour. As several authors have suggested a more aggressive nature of this tumour, data relating to the histogenesis, clinical behaviour and prognosis of this tumour need to be more extensively studied. Whether to consider this tumour as a variant of ameloblastoma or a hybrid tumour of ameloblastoma and AOT still remains to be answered.
 
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TABLES AND FIGURES