Recurrent head and neck desmoplastic melanoma with perineural spread along the nervus mandibularis revealed by 18F-FDG PET/CT

Abstract

This report describes a rare case of recurrent head and neck desmoplastic neurotropic melanoma with perineural spread along the nervus mandibularis. An 87-year-old male presented with a rapidly growing mass on the right side of the chin, 4 years after surgical excision of a desmoplastic non-melanotic melanoma of the tip of the chin, with lymphadenectomy of the right side submental and submandibular areas. A panoramic X-ray showed extensive widening of the mandibular canal compatible with perineural tumour growth. 18 F-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography/computed tomography (PET/CT) images revealed intense pathological uptake in the recurrent tumour mass located in the right lower buccal fold, and linear pathological uptake in the mandibular canal. Although magnetic resonance imaging is considered the standard of reference, recognition of perineural spread on 18 F-FDG PET/CT is important, as it usually leads to a change in patient management from cure to palliation and may avert further diagnostic procedures.

Introduction

Growth away from the primary tumour site along the pathway of peripheral nerves is known as perineural spread. Perineural spread is a well-described complication of head and neck malignancies. Most cases occur in squamous cell carcinoma due to its high incidence among all head and neck cancers. Perineural tumour spread is also particularly recognized in adenoid cystic carcinoma. The presence of perineural spread has a great clinical impact on patient management, regardless of the histological subtype, as it is associated with a poor prognosis and a higher risk of local recurrence and metastasis. Therefore, treatment goals usually change from cure to palliation. Furthermore, it may not be recognized at the time of surgery and it may occur in the absence of hematogenous or lymphatic metastasis.

Although 18 F-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography/computed tomography (PET/CT) is nowadays part of the initial work-up and follow-up of patients with head and neck cancer, a limited number of cases have been reported demonstrating the diagnosis of perineural spread using 18 F-FDG PET/CT. In this case report we describe a rare case of perineural spread of head and neck melanoma and its imaging features on 18 F-FDG PET/CT.

Case report

An 87-year-old male presented with a rapidly growing mass on the right side of the chin accompanied by increasing numbness of the right mental region. Four years earlier he had undergone surgical excision of a desmoplastic non-melanotic melanoma of the tip of the chin, with lymphadenectomy of the right side submental and submandibular areas.

On clinical examination, a subcutaneous growing mass was palpated at the site of the previous surgery, with extension into the oral cavity. Intraoral examination revealed a multilobular mass in the lower buccal fold of the right premolar region, being an extension of this tumour. Histopathological examination of a biopsy specimen obtained intraorally confirmed the clinical suspicion of tumour recurrence.

On an initially taken panoramic X-ray, extensive widening of the mandibular canal was observed, compatible with perineural tumour growth ( Fig. 1 ). 18 F-FDG PET/CT images revealed intense pathological uptake in the recurrent tumour mass located in the right lower buccal fold, and linear pathological uptake in the mandibular canal almost to the base of the skull, but without involvement of the trigeminal ganglion ( Fig. 2 ). In this specific situation, surgical treatment was no longer considered to be curative. Due to the threat of tumour growth through the skin, palliative treatment with 5 × 4 Gy irradiation was started. The nerve trunk of the trigeminal ganglion and the skull base were not within the field of irradiation to stop the perineural spread.

Fig. 1
A panoramic X-ray showing extensive widening of the mandibular canal compatible with perineural tumour growth.

Fig. 2
Hybrid 18 F-FDG PET/CT images showing the corresponding sagittal PET, hybrid PET/CT, and CT slices, with the CT slice in the ‘skeletal’ setting. Pathological uptake is observed in a linear pattern in the widened right mandibular canal, without involvement of the trigeminal ganglion.

Case report

An 87-year-old male presented with a rapidly growing mass on the right side of the chin accompanied by increasing numbness of the right mental region. Four years earlier he had undergone surgical excision of a desmoplastic non-melanotic melanoma of the tip of the chin, with lymphadenectomy of the right side submental and submandibular areas.

On clinical examination, a subcutaneous growing mass was palpated at the site of the previous surgery, with extension into the oral cavity. Intraoral examination revealed a multilobular mass in the lower buccal fold of the right premolar region, being an extension of this tumour. Histopathological examination of a biopsy specimen obtained intraorally confirmed the clinical suspicion of tumour recurrence.

On an initially taken panoramic X-ray, extensive widening of the mandibular canal was observed, compatible with perineural tumour growth ( Fig. 1 ). 18 F-FDG PET/CT images revealed intense pathological uptake in the recurrent tumour mass located in the right lower buccal fold, and linear pathological uptake in the mandibular canal almost to the base of the skull, but without involvement of the trigeminal ganglion ( Fig. 2 ). In this specific situation, surgical treatment was no longer considered to be curative. Due to the threat of tumour growth through the skin, palliative treatment with 5 × 4 Gy irradiation was started. The nerve trunk of the trigeminal ganglion and the skull base were not within the field of irradiation to stop the perineural spread.

Jan 19, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Recurrent head and neck desmoplastic melanoma with perineural spread along the nervus mandibularis revealed by 18F-FDG PET/CT
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