Intraosseous mucoepidermoid carcinoma of mandible: a rare case presentation and literature review

Abstract

Intraosseous mucoepidermoid carcinoma (IMC) is an atypical salivary gland neoplasm commonly seen in middle-aged adults. Their presentation in young individuals below the age group of 20 years is sporadic. Treatment modality mainly includes radical surgical resection for malignant tumours. There were only 13 reported cases of IMC of mandible below the age of 20 years in the English literature. All the reported cases were only managed with wide resection and radiotherapy. Surgical resection leads to loss of form and function in the young population, decreasing their morale. Hence, reconstruction should be mandated in young individuals for restoring function and aesthetics. We present a case of IMC of the mandible in a young female individual resected and reconstructed with a free fibula bone graft. Satisfactory healing is elicited with no recurrence at the 2-year follow-up period.

Background

Salivary gland neoplasms account for about 3%–4% of all head and neck cancers.¹ Mucoepidermoid carcinoma (MC) is the most common neoplasm in major and minor salivary gland neoplasms, constituting about 34% and 12% of all salivary gland tumours.² The largest major parotid salivary gland is the conventional site for about 89.6% of cases, as given by Eversole.³ Intraosseous MC (IMC) is a rare tumour of the jawbones, constituting 2%–4%, of which the posterior mandible is most commonly affected.⁴ Treatment modality mainly includes radical surgical resection, which leads to loss of form and function in the young population. Hence, reconstruction is aimed at improving the quality of life. Revascularised free fibula flap as a bone graft developed a keystone in head and neck reconstructive surgeries of resected benign or malignant tumours, osteomyelitis or osteoradionecrotic mandible.⁵ Furthermore, autogenous bone grafts with microsurgical techniques have transformed mandibular reconstruction in oral cancer surgeries.⁶

We present a case of a young woman with low-grade IMC diagnosed, surgically treated with segmental mandibular resection and mandibular shape reconstruction done with vascularised fibular osteomyocutaneous flap and bone graft. According to the authors’ knowledge, this is the first case report in the English literature where an IMC of the mandible is reconstructed with a free fibula graft in an individual with less than 20 years.

Case presentation

A young female individual presented to the Department of Oral and Maxillofacial Surgery at G.S.L Dental College and Hospital, Rajamahendravaram, with a chief complaint of pain in the left lower back tooth region for 20 days. The pain was insidious on the onset, continuous and lancinating, which aggravates mastication and is not relieved on medication. There was no significant medical and personal history. The patient was subjected to routine general systemic examination. No significant extraoral findings were noted. Intraoral examination revealed the swelling with a dimension of 2×3 cm extending from the left mandibular second molar to the retromolar region. Tenderness on palpation is elicited in the left ramus of the mandible. There was a missing left third molar (figure 1). The mucosa clinically appeared erythematous with a mild bluish hue.

Figure 1.

Intraoral swelling extending from the left mandibular second molar to retromolar region, anteroposteriorly from the buccal vestibule to the lingual vestibule of the mandibular ramus with missing third molar.

Investigations

Orthopantomography (figure 2) reveals a well-defined radiolucent lesion involving unerupted left third molar, body and ramus of mandible measuring approximately 3×3 cm in size appearing as a dentigerous cyst. Cone-beamed CT (CBCT) (figure 3) illustrated ill-defined radiolucency measuring 16.0 mm × 10.8 mm (Mesio-Distal × Bucco-Lingual) in the region of the left lower posterior aspect of the mandible. Contrast-enhanced CT (CECT) of head and neck revealed ill-defined heterogeneously enhancing lesion with few non-enhancing necrotic areas measuring approximately 2.8×2.2×3.0 cm (antero−posterior × transverse × cranio-caudal) noted in the region of the posterior aspect of left gingivo-buccal sulcus extending into left retromolar trigone involving left medial pterygoid. Posteroinferiorly, the lesion is abutting the left submandibular gland with intact fat planes. Bone erosion of posterior aspect of left inferior alveolus adjacent to the molar tooth probable of malignancy. Subcentimetric mildly enhancing nodes measuring approximately 1.4×0.6 cm noted in left IB (sub mandibular) level probable of metastasis. Incisional biopsy was done in the same region, and histopathologic examination revealed it as IMC.

Figure 2.

Orthopantomography reveals a well-defined radiolucent lesion involving impacted left third molar, body and ramus of the mandible.

Figure 3.

CBCT illustrates ill-defined radiolucency in the region of the left lower posterior aspect of the mandible.

Differential diagnosis

The provisional diagnosis is given as dentigerous cyst based on history, clinical and radiographic examinations. Differential diagnoses include aneurysmal bone cyst, ameloblastoma, keratocystic odontogenic tumour. In addition, CBCT and CECT illustrated ill-defined radiolucent-enhancing malignant lesions probable of MC, adenoid cystic carcinoma or acinic cell carcinoma, which could not be entirely excluded until the histopathological assessment is performed. The subsequent histological examination indicated the final diagnosis of low-grade IMC.

Treatment

Under general anaesthesia, the surgical plan was executed as segmental mandibular resection with modified functional neck dissection involving levels I, II, III and IV on the left side (figure 4). Segmental resection of the mandible was done from 34 regions to the left ramus, not involving the coronoid process and temporomandibular joint. The defect reconstruction is done with a free fibula (figure 5) and fixed with a titanium mandibular reconstruction plate and screws (figure 6). The specimen was sent for histopathological examination (figure 7). Histology of the excisional biopsy reveals sheets of dysplastic epidermoid cells in the fibrous connective tissue stroma. These epidermoid cells showed cystic degenerative changes in many areas. The acinar cells were showing mucin secretions. Focal areas showed clear cells. The lesion was diagnosed as low-grade IMC of the mandible (figure 8).

Figure 4.

Segmental mandibular resection with modified functional neck dissection involving levels I, II, III and IV on the left side was performed.

Figure 5.

Free fibular graft is procured for defect reconstruction.

Figure 6.

The defect was reconstructed with a free fibula graft, fixed with a titanium mandibular reconstruction plate and screws.

Figure 7.

The excised specimen.

Figure 8.

Histopathological specimen revealed sheets of dysplastic epidermoid cells in the fibrous connective tissue stroma that showed cystic degenerative changes in many areas.

Outcome and follow-up

The postoperative healing in the reconstructed site was uneventful in the follow-up period of 1 year with no recurrence. During the follow-up reviews, no donor site morbidity was noticed after the free fibula harvested region. A periodic follow-up done at 3-months intervals (figure 9).

Figure 9.

Orthopantomography after 1 year of surgery.

Discussion

Salivary gland tumours are rare, and the incidence varies between 0.3 and 4 per 1 00 000. The most typical malignant salivary gland tumours type is MC. MC is a distinct pathological entity based on its mucous-secretion and epidermal cellular elements. According to Eversole et al,³ MC can be elicited in the submandibular gland 8.4%, in the sublingual gland 0.4%, and palatal minor salivary gland 41.1%, followed by the buccal mucosa, tongue, lips, retromolar gap, the floor of the mouth, sinuses and larynx.⁷ Two to three times higher frequency is noted for the mandible than the maxilla.⁸ According to Eversole et al,³ about half of the MC of the mandible are related to impacted teeth⁹ and dental cysts.⁷

IMC is a well-recognised salivary gland tumour, and in 1939, Lepp first reported in the mandible in a 66-year-older woman.¹⁰ Primary or central IMC is rare in young individuals with the highest prevalence in the fourth and fifth decades of life.¹¹ IMC in primary intraosseous carcinomas of the jaw is classified as type 4.¹² This was based on the histological findings of MC of the gnathic, similar to salivary gland MC, and it was thought to be arising from epithelial remnants of the odontogenic cyst.⁹ The clinical features of IMC indicate that females are twice more susceptible as males. The lesion shows a highly varying clinical response ranging from slow to metastatic tumours of low grade to aggressive nature, including pain, swelling, trismus, tooth mobilities and altered sensations of inferior alveolar nerve. Occurrence in children is rare, and both mandible and maxilla are equally affected. The tumour shows a tendency to occur at puberty, suggesting a hormonal impact on salivary glands.¹¹

MC was traditionally classified into three histopathological grades: low, intermediate and high-grade tumours. Low-grade tumours are highly differentiated neoplasms with a predominance of macro and microcysts. Intermediate-grade tumours consist of predominately intermediate cells and few cysts, mucin-producing, and islands of epidermoid cells. Finally, high-grade tumours are undifferentiated neoplasia consisting of most intermediate and epidermoid cells in solid blocks and mucin-producing cells.¹²

Radiographic imaging modalities play a crucial role in differentiation and detection due to the asymptomatic presentation of IMC. According to Chan et al, radiographic features of the IMC include well-defined sclerotic margins with an amorphous internal sclerotic bone and several minor locules.¹³ Additionally, the aggressive nature of the tumour showed by cortical bulging, perforation of the cortical bone, and invasion of the tumour to surrounding soft tissues, with the displacement of the tooth and root resorptions. Furthermore, the exact mechanism of the pathogenesis of IMC is unknown, and numerous hypothetical theories of the origin are speculated, including neoplastic alteration of the trapped minor salivary glands in the maxilla and retromolar mucous glands in the mandible. In addition, the maxillary sinus lining undergoes neoplastic alterations and invasion and the presence of trapped embryonic remnants of the submandibular and sublingual salivary glands in the mandible.¹²

The surgical treatment modality for IMC includes curettage, enucleation, marsupialisation and resection. For low-grade tumours, IMC must be treated by wide local resection, en bloc resection or hemimandibulectomy or hemimaxillectomy; notably, the negative margin should be emphasised in primary lesion to avoid local recurrence. For high-grade tumours, radiotherapy is recommended, and neck dissection is performed in the presence of a positive lymph node. Neck dissection is therapeutic, performed for patients with regional lymph node metastasis occurs in approximately 10% of cases, and an elective is recommended for patients with high-grade tumours with a risk of having occult cervical nodal metastases that exceed around 15%–20% of the cases. Freije et al proposed the need for adjuvant radiotherapy solely for high-grade tumours.¹⁴ Their location and extent evaluate the approach for the reconstruction of mandibular defects. Jewer classification reflects the complexity of the mandibular defect’s reconstruction challenge. The central defects, consisting of bilateral canines, are assigned ‘‘C’’, and the lateral segments excluding the condyle are assigned ‘‘L’’. The condyle resection along with the lateral mandible is assigned ‘‘H’’, or hemimandibular. Eight combinations of these capital letters—C, L, H, LC, HC, LCL, HCL and HH, have come across. The lateral defect can be reconstructed with a linear section of bone, while central defects are restored with osteotomies. The ideal reconstructed mandibular arch would articulate the maxillary arch in restoring normal functions such as speech, mastication, swallowing and aesthetic appearance. Following the mandibular segmental resection, the functional and aesthetic outcomes are closely related to the technique used during mandibular reconstruction with bone graft. In addition, it should restore the skeletal structure, both the external and internal soft tissues, and provide oral health rehabilitation.⁶

The fibula bone is the most commonly utilised donor bone available for adequate harvest to reconstruct complete jaw resection, support dental implantation and restore the height of the mandible in the maxillofacial profile. In addition, it is used for the reconstruction of the lateral segment and anterior arch of the mandible. Furthermore, it can be harvested with skin island to reconstruct mucosa and skin defects along with muscle cuff of soleus. The blood supply to the fibula bone receives from the peroneal artery branch of the tibioperoneal trunk via endosteal and periosteal branches. The free fibular flap was initially adapted to mimic the mandible shape and restore segmental mandibulectomy defects.¹⁵ The main advantage of the fibula bone graft, donor site morbidity is meagre compared with other donor sites. Furthermore, ankle joint instability does not occur if a distal portion is at best 7 cm of the fibula, involving the tibiofibular syndesmosis. Flexion deficiency of the hallux has not been observed following the resection of flexor hallucis longus muscle. In addition, the lower lateral leg offers large amounts of thin and pliable skin that can be transferred in a sensate fashion.¹⁶

IMC is a rare bone tumour with only 136 reported cases in English literature since its first description. The incidence of IMC is significantly less in patients of age below 20 years. Table 1 illustrates the literature review for IMC of mandible below 20 years.

Table 1.

Review of literature based on chronological patient age for intraosseous mucoepidermoid carcinoma of mandible below 20 years

S. no	Author	Year	Age (in years)	Gender	Site	Treatment
1	Bhaskar et al17	1963	1	Female	Body	Marsupialisation, excision and partial resection
2	Brookstone and Huvos17	1992	10	Male	Body	Radiotherapy
3	Ezsias et al17	1994	11	Female	Angle	Mandibulectomy
4	Arenas et al10	2019	13	Male	Body	Hemimandibulectomy, neck dissection and radiotherapy
5	Current et al17	2004	14	Male	Body	Mandibulectomy
6	Baj et al17	2002	15	Male	Body	Mandibulectomy
7	Zhou et al2	2011	16	Female	Body	Partial mandibulectomy and radiotherapy
8	Freitas et al1	2018	16	Male	Body and angle	Partial mandibulectomy and radiotherapy
9	Decarvalho et al18	2020	16	Male	Body and angle	Surgery
10	Alexander et al19	1974	18	Male	Ramus	En bloc excision
11	Bell et al2	2016	18	Male	Body	Mandibulectomy
12	Zhou et al2	2011	19	Female	Body	Partial mandibulectomy
13	Hertz20	1952	20	Female	Third molar area	Excision, resection and irradiation

In this study, IMC is reconstructed by free fibula bone graft with a follow-up period of 2 years with no recurrence in a young female patient. In addition, adequate healing was observed in the reconstructed site. Success and survival rates of patients with low-grade tumours are 92%–100%. They cannot be easily differentiated from primary dentigerous tumours of the jaw. Careful clinical-radio and histopathological evaluation are essential for prompt definitive diagnosis. It is better to perform a biopsy before any curative therapy for management. The importance of radical surgical resection in the effectively managing of transformed neoplastic tissues is well emphasised.

Learning points.

• Central or primary intraosseous mucoepidermoid carcinoma is sporadic in young individuals.

• Reconstruction of the surgical defect should be given utmost importance in younger individuals restoring aesthetics and function.

• Free fibula bone graft offers an excellent reconstruction of the resected mandible with no or less donor site morbidity.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s)