Peripheral dentinogenic ghost cell tumour

Abstract

The dentinogenic ghost cell tumour (DGCT) is a rare benign neoplasm, which histologically presents itself as an aberrant keratinisation of the epithelium, ghost cells and dentinoid material. Depending on its location there are two different types of DGCT, central or peripheral, with different clinical characteristics. By 2019, there were only 57 cases of DGCT published: 39 of the central type and 18 of the peripheral type.

In this clinical case, the authors describe the case of a 78-year-old man with a painless and slow growing mandibular lump. The diagnosis of peripheral DGCT was made by incisional biopsy and the treatment consisted of radical excision with upper marginal mandibulectomy.

The aim of the article is to report a clinical case of a rare pathology and, consequently, to help diagnose and better understand its biological behaviour.

Background

Dentinogenic ghost cell tumour (DGCT) is a rare benign epithelial and mesenchymal neoplasm, which is characterised histologically by aberrant keratinisation of the epithelium, a variable number of ghost cells and the presence of dentinoid material.¹

This tumour usually appears between the second and ninth decade of life, with a higher incidence between 40 and 50 years of age.² Some authors report a higher prevalence in men.^{2 3} Additionally, most of the reported cases (65%) are found in the Asian population.²

Two types of DGCT are described: central and peripheral.^{2 4} Central DGCT presents itself as an intraosseous tumour, preferably involving the region between the canine tooth and the first mandibular molar. On the other hand, peripheral DGCT, characterised for being extraosseous and occuring in the alveolar ridge mucosa, are more frequently found in the anterior region of the mandible.² The peripheral type is relatively less common and less aggressive when compared with the central type.^{2 4}

In 2019, there were only 57 published cases of DGCT: 39 of the central type and 18 of the peripheral type.²

The authors describe a clinical case of peripheral DGCT diagnosed in a 78-year-old male patient.

Case presentation

A 78-year-old man presented to the Stomatology and Maxillofacial Surgery Department of the Portuguese Institute of Oncology of Coimbra (IPO-Coimbra) referred by his attending physician, due to a painless mass located in the anterior alveolar ridge of the mandible, with haemorrhagic spots, and approximately 6 years of evolution and progressive growth.

On examination, the edentulous patient presented a nodule of hard-elastic consistency on the left mandibular ridge, in a paramedian location with about 4 cm of longest axis. It showed some areas of erosion, probably due to masticatory trauma, but no haemorrhaging was present (figure 1). Ill-fitting removable dentures were present.

Figure 1.

Initial intraoral clinical examination.

His medical history revealed a background of surgery for an intestinal malignant neoplasm several years prior and smoking habits (45 pack per year). He did not take any chronic medication.

Investigations

In the orthopantomography, there was an area of soft tissue density compatible with the lesion observed on clinical examination and a radiotransparent region with infralesional radiopaque areas (figure 2).

Figure 2.

Initial orthopantomography (yellow arrow indicates area with soft tissue density; red arrow points to radiotransparent region with radiopaque areas).

In view of the clinical and imaging findings, an incisional biopsy of the nodular lesion was performed. The anatomopathological findings identified clusters of ghost cells surrounded by pavement cells with a basal columnar layer and the presence of abundant dentinoid material, compatible with the diagnosis of ghost cells dentinogenic tumour.

Treatment

In view of the pathology in question, the authors decided to surgically approach the lesion with the intention of radical excision. Thus, under general anaesthesia and nasotracheal intubation, the lesion was excised, and superior marginal mandibulectomy was preformed (figures 3 and 4). The ill-fitting dentures were discarded.

Figure 3.

Surgical site after excision of the lesion.

Figure 4.

Neoplasm after excision.

Outcome and follow-up

The anatomopathological examination of the surgical specimen identified a proliferation of the ameloblastomatoid type, keratinisation with the presence of ghost cells and foci of calcification, confirming the diagnosis revealed in the incisional biopsy (figure 5).

Figure 5.

(A) Histological image compatible with DGCT (He 5 x); (B) odontogenic epithelium with dentinoid material (*) and ghost cells (black arrow) (He 20 x); (C) odontogenic epithelium with ameloblastoma-like characteristics infiltrating the peripheral connective tissue, with dentinoid material (*) and ghost cells (black arrow) (He 20 x); (D) high power view of dentinoid material (*), ghost cells (black arrow) and foci of calcification (yellow arrow) (He 80 x).

Ten months after surgery, the patient had no complaints and the surgical site healing was progressing well, with no sign of recurrence or other complications (figures 6 and 7).

Figure 6.

Orthopantomography 10 months after surgery.

Figure 7.

Intraoral clinical examination 10 months after surgery.

Long-term follow-up of the patient will be done, according to the institution’s protocol, in order to control possible neoplasm recurrence.

Discussion

Calcifying odontogenic cyst (COC) was first described by Gorlin et al in 1962.⁵ Later, in 1981, Praetorius et al suggested the term ghost cell dentinogenic tumour to differentiate this lesion from COCs, because despite showing the characteristics of a cystic lesion, it also had several characteristics of a solid neoplasm.⁶ Later, in 2005, DGCT was introduced in the histological category of odontogenic tumours by the WHO.^{7 8}

The term ‘ghost cells’ was introduced in 1946 by Thoma and Goldman, because microscopically, these epithelial cells had aberrant and anucleated forms.⁹

Lesions such as COC, DGCT and odontogenic ghost cell carcinoma (OGCC) represent a group of odontogenic lesions of the jaws characterised by the presence of ghost cells.³

In the most recent classification published by the WHO in 2017, COC is defined as a simple developmental cyst. On the other hand, DGCT represents a benign mixed, epithelial and mesenchymal neoplasia. OGCC appears as the malignant variant of these lesions.¹

DGCT, being a solid variant of calcified odontogenic cysts (COC), is extremely rare, as COCs represent only 1%–2% of all odontogenic cysts and only 2%–14% of them are DGCT.²

Unlike most odontogenic tumours, the pathogenesis of DGCT is not yet known.²

DGCT has been classified into two types, central or peripheral, according to its location. Central DGCT is the most common.^{3 4 10}

While the central intraosseous DGCT is highly aggressive and subject to local recurrence, the peripheral DGCT is relatively insidious and with no reported cases of recurrence.²

According to the literature, peripheral DGCT occurs more frequently in individuals over 50 years of age and manifests itself mostly in the mandible. Clinically, it presents as a painless exophytic mass in the gingiva or mucosa of the alveolar ridge (in edentulous patients). Most reported cases of the peripheral type (67%) are asymptomatic, reflecting their low aggressiveness.^{2 10}

Radiographically, DGCT is characterised as a radiotransparent or radiotransparent/radiopaque region (depending on the amount of calcification), with well to poorly defined limits and mostly unilocular.^{2 4}

The histopathology of these lesions is essential for their correct diagnosis. Histologically, the presence of numerous ghost cells and dentinoid material are essential for the diagnosis of DGCT. These characteristics are also important to distinguish them from conventional ameloblastoma and other odontogenic tumours.^{2 10 11}

Ghost cells are believed to be transformed odontogenic epithelial cells. Although the presence of ghost cells is a typical feature for the diagnosis of DGCT, these cells can also be seen in other odontogenic tumours.^{10 11} The nature of the dentinoid material found in DGCT is unknown. It is an amorphous eosinophilic material containing widely separated cell bodies. It does not have the tubular structure of normal dentin and appears as an irregular mass within the connective tissue adjacent to the proliferation of the odontogenic epithelium.¹¹

Thus, in DGCT, biopsy becomes a fundamental diagnostic tool, as it allows the differential diagnosis with other more common lesions.¹¹

The two types of DGCT (central and peripheral) have similar histological exams, as so the clinical presentation is essential for their distinction.¹²

Another relevant differential diagnosis is the malignant form, the OGCC, where numerous mitoses are found. The absence of mitosis in DGCT eliminates the possibility of malignancy.³

Malignant transformation of a DGCT into an OGCC is rare.⁸

In this clinical case, the authors describe the presence of an exophytic tumorous mass in the edentulous area of the anterior mandibular region, with mostly extraosseous involvement, slow evolution (6 years) and practically asymptomatic. The anatomopathological examination of the lesion confirmed that it was a DGCT. Considering these clinical characteristics of the tumour, as well as the patient’s advanced age, this lesion fits into a peripheral type DGCT.

The small number of reported cases does not allow conclusions to be drawn about the ideal treatment. However, due to the difference in the recurrence rate, treatment should be different depending on the type of DGCT. The treatment of choice for peripheral DGCT is local excision, as it has no reported recurrence; on the other hand, central DGCT requires en bloc resection or segmental resection with an adequate surgical safety margin, as it is considered a locally aggressive neoplasm and has a recurrence rate of 73% after conservative surgical treatment (enucleation or curettage).^{2 8}

In the clinical case presented, as it is a peripheral DGCT, a conservative surgical approach was chosen, with excision of the tumour with marginal mandibulectomy because of the bone damage that was present.

Learning points.

• Dentinogenic ghost cell tumour (DGCT) is a rare lesion with well-defined histological characteristics, biopsy is essential for its diagnosis.

• The two types of DGCT (central and peripheral) have similar histological exams, as so the clinical presentation is essential for their distinction.

• An appropriate surgical intervention for each type of DGCT are the pillars for the successful treatment of these patients.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).