Acinic cell carcinoma of ascending ramus mandible: a rare case report

INTRODUCTION

Nasse in 1892 described for the first time an uncommon low-grade malignant tumor i.e., acinic cell carcinoma of salivary glands.¹ This acinic cell carcinoma is an unusual, low-grade, malignant salivary gland tumor with approximately almost 90% arising in the parotid gland central ACC of the jaw is an extremely rare neoplasm and exhaustive literature review could reveal only 8 such cases.¹

CASE REPORT

A 77 years elderly male presented in the otorhinolaryngology outpatient clinic of Dayananand Medical College and Hospital with an oval swelling on the check on the right side of 5 months duration (Figure 1).

The swelling was localized to the region of the ascending ramus of the mandible about 3x2 cm in size and was soft on palpation. The overlying skin on the extrinsic and the buccal mucosa on intrinsic examination was freely mobile. There was no accompanying trismus. The neck was clinically negative for any neck nodes. Patient’s medical history was unremarkable. There was no history of any substance abuse or addictions.

Th computed tomography was reported as a lytic expansile lesion involving the body and ramus of the right mandible with a large associated soft tissue component. thin bony fragments seen at the periphery of the soft tissue. The right parotid gland was separate from the lesion (Figure 2 a and b).

Magnetic resonance imaging with contrast reported a large well defined lobulated lesion appearing hypointense on t₂ weighted imaging seen in the masseteric space extending into infratemporal fossa measuring 7.1 x 4.4 x 4 cm in size, showing diffusion restriction with destruction of the ramus of the mandible, altered signal intensity appearing hypointense on t₁ and showing post contrast enhancement involving body of mandible on right side .masseter muscle was displaced laterally by the lesion and right parotid gland was separate from the lesion and was compressed by the mass (Figure 3a and b).

Fine needle aspiration of the swelling reported as malignant aspirate - category vi - possibly acinic cell carcinoma (Milan system of reporting). the smear showed tumor cells arranged as papillary clusters, acinar pattern and dispersed population with individual tumor cells displaying moderate nuclear pleomorphism, anisonucleosis, round nuclei and moderate amount of ill-defined granular cytoplasm.

He was taken up for comprehensive neck dissection with clearance of level I to level v lymph nodes. The ascending ramus of the mandible beyond the first premolar was found to be eroded by the tumour and removed, along with the coronoid process.

Haemostasis was achieved by ligating the inferior alveolar artery and bipolar diathermy of the pterygoid venous plexus of infratemporal fossa (Figure 5).

The buccal mucosa and buccinator were not breached. The defect so created was left as such and wound sutured over an indwelling drain.

DISCUSSION

2% of the salivary gland tumors arise from the acinic cells. This Acinic cell carcinoma is an unusual, low-grade, malignant salivary gland tumor with approximately almost 90% arising in the parotid gland. The rest involve the submandibular and the minor salivary gland.¹

Acinic cell carcinoma was first described by Godwin et al in 1954.² Origin of this entity primarily in maxillofacial bony skeleton is rare. This Acinic cell carcinoma has been seen in the mandible more as compared to other sites. Mandibular intraosseous presentation of acinic cell salivary gland carcinoma has an incidence of about 75% with a peak age in the 5^th and 6^th decade of life Though all age groups may be affected.³

Local complaints of pain and swelling of the involved area is usually the presenting symptom. The present case was a 77 years old male with a swelling on the cheek minus any pain for which he underwent partial mandibulectomy and a comprehensive neck dissection.

Acinic cell carcinoma in the mandible has female predeliction as reported by Hiremath et al, Nakazawa et al.^4,5 Hence our finding in the 77 years old male is rare. Barnes et al described two theories for the central salivary gland neoplasms; one suggests a neoplastic transformation in developmentally entrapped salivary gland tissue in the bone and the other suggests a metaplasia of epithelial lining of an odontogenic cyst.⁶ The present case belonged to the first category.

Surgery is the treatment of choice for central acinic cell carcinoma and postoperative radiotherapy may be useful for recurrent, undifferentiated cases of acinic cell carcinoma, positive margins and advanced tumours with cervical node spread the present case was treated surgically.⁷

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: Not required

REFERENCES

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