Neurotropic melanoma: the management of localised disease

Abstract

Neurotropic melanoma is a rare subtype of cutaneous malignant melanoma. Compared with conventional melanoma, it is more locally aggressive with an increased tendency for local recurrence but less likely for nodal or distant metastases. These tumours can be a diagnostic dilemma with a variety of morphological, histopathological, and immunophenotypical expressions. The often amelanotic, benign appearance may lead to treatment issues such as late presentation, diagnostic delay, misdiagnosis, insufficient surgical margins, and recurrence with resulting poor outcome. The neurotropic nature of the disease and prevalence in the head and neck region can result in perineural and neural invasion along named large nerves into the brain with resulting neuropathies. Wide local excision with adjuvant radiotherapy where indicated remains the current practice for treatment with chemotherapy predominately being reserved as a salvage treatment for patients with disseminated disease.

Figure 1

T1 Axial Fat Saturated, Gadolinium enhanced MRI scan of the head. This image displays the case of a 48-year-old man with a previous excision of a neurotropic melanoma of the face. Approximately one year from wide local excision he presented with facial pain and biopsy proven recurrence of neurotropic melanoma involving the mandibular division of the trigeminal nerve, filling the cavernous sinus and prepontine cistern with obvious brainstem compression.

Figure 2

Low power (×20) view of skin with epidermis on the left and subcutis on the right. At this magnification we can identify nodules within the subcutis: at the centre, at the bottom, centre top, and on the right in the middle.

Figure 3

High power (×400) view of a nodule shows a nerve (bottom half) surrounded by melanoma (darker spindle cells on the left and top). The tumour cells at the top of the picture are arranged in a fasciculated (bundled) growth pattern, similar to the nerve next to it.