Neurotropic malignant melanoma presenting as a trigeminal sensory neuropathy

Melanoma metastasis to the femoral nerve: a novel case of melanoma masquerading as mononeuropathy. Illustrative case

BACKGROUND

Metastatic cancer may involve the central and peripheral nervous system, usually in the late stages of disease. At this point, most patients have been diagnosed and treated for widespread systemic disease. Rarely is the involvement of the peripheral nervous system the presenting manifestation of malignancy. One reason for this is a proposed "blood-nerve barrier" that renders the nerve sheath a relatively privileged site for metastases.

OBSERVATIONS

The authors presented a novel case of metastatic melanoma presenting as intractable leg pain and numbness. Further workup revealed concurrent disease in the brain and breast, prompting urgent treatment with radiation and targeted immunotherapy.

LESSONS

This case highlights the rare presentation of metastatic melanoma as a mononeuropathy. Although neurological complications of metastases tend to occur in later stages of disease after initial diagnosis and treatment, one must remember to consider malignancy in the initial differential diagnosis of mononeuropathy.

Neoplastic nerve lesions

Though metastasis and malignant infiltration of the peripheral nervous system is relatively rare, physicians should have a familiarity with their presentations to allow for prompt diagnosis and initiation of treatment. This article will review the clinical presentations, diagnostic evaluation, and treatment of neoplastic involvement of the cranial nerves, nerve roots, peripheral nerves, and muscle. Due to the proximity of the neural structure traversing the skull base, metastasis to this region results in distinctive syndromes, most often associated with breast, lung, and prostate cancer. Metastatic involvement of the nerve roots is uncommon, apart from leptomeningeal carcinomatosis and bony metastasis with resultant nerve root damage, and is characterized by significant pain, weakness, and numbness of an extremity. Neoplasms may metastasize or infiltrate the brachial and lumbosacral plexuses resulting in progressive and painful sensory and motor deficits. Differentiating neoplastic involvement from radiation-induced injury is of paramount importance as it dictates treatment and prognosis. Neurolymphomatosis, due to malignant lymphocytic infiltration of the cranial nerves, nerve roots, plexuses, and peripheral nerves, deserves special attention given its myriad presentations, often mimicking acquired demyelinating neuropathies.

Plexus and peripheral nerve metastasis

Cancer in the form of solid tumors, leukemia, and lymphoma can infiltrate and metastasize to the peripheral nervous system, including the cranial nerves, nerve roots, cervical, brachial and lumbosacral plexuses, and, rarely, the peripheral nerves. This review discusses the presentation, diagnostic evaluation, and treatment options for metastatic lesions to these components of the peripheral nervous system and is organized based on the anatomic distribution. As skull base metastases (also discussed in Chapter 14) result in cranial neuropathies, these will be covered in detail, as well as cancers that directly infiltrate the cranial nerves. Particular emphasis is placed on the clinical, imaging, and electrodiagnostic features that differentiate neoplastic plexopathies from radiation-induced plexopathies. Neurolymphomatosis, in which malignant lymphocytes invade the cranial nerves, nerve roots, brachial and lumbosacral plexuses, and peripheral nerves, is a rare manifestation of lymphoma and leukemia. Diagnoses of neurolymphomatosis are often missed or delayed given its varied presentations, resulting in poorer outcomes. Thus this disease will also be discussed in depth.

Metastases to the peripheral nervous system

Cancer metastasis can affect any part of the nervous system. When the peripheral nervous system is involved, the usual targets are cranial nerves, nerve roots and plexi. However, peripheral nerves and muscles can also be affected by compression or infiltration of neoplastic cells. This review focuses in the diagnosis and treatment of metastatic complications of cancer involving plexi, peripheral nerves and muscles.

Neurotropic Melanoma of the Head and Neck With Clinical Perineural Invasion

OBJECTIVE

The purpose of this article is to report our experience with neurotropic melanoma, a rare malignancy that sometimes produces neurologic symptoms because of a direct extension of the primary tumor.

METHODS

We report 3 consecutive patients with neurotropic melanoma of the head and neck who presented with clinical perineural invasion.

RESULTS

Two patients had incompletely resectable tumors and were treated with definitive radiotherapy (RT), and 1 patient received surgery and postoperative RT. One patient experienced recurrence in a regional lymph node 30 months after RT and underwent salvage surgery; he is disease-free at 45 months after initial treatment. The remaining 2 patients are disease-free 34 months and 14 months after treatment.

CONCLUSIONS

Radiotherapy alone or combined with surgery may provide relatively long-term local control in patients who have neurotropic melanoma with clinical perineural invasion.

Perineural invasion of cutaneous malignancies

BACKGROUND

Perineural invasion is an important mode of tumor spread and is associated with increased aggressiveness and a propensity for recurrence among cutaneous malignancies.

OBJECTIVE

To review the pathogenesis, diagnosis, and treatment of cutaneous tumors exhibiting perineural invasion.

METHODS

This article is based on a review of the medical literature concerning tumors with perineural involvement.

RESULTS

This article describes the clinical signs and histologic features of cutaneous malignancies exhibiting perineural involvement.

CONCLUSION

Appropriate patient care mandates consideration of perineural invasion in the evaluation of cutaneous tumors. As the majority of patients present without symptoms of neural involvement, physicians must be vigilant in the search for this type of tumor spread.

Intraneural nerve metastasis with multiple mononeuropathies

Although cancer is a frequent condition, neoplastic involvement of the peripheral nervous system is rare. The mechanisms are heterogeneous and include lesions within the cerebrospinal fluid (CSF) space, local invasion (e.g. brachial plexus), compression, rarely direct infiltration, perineurial spread and even rarer intranerval metastasis. A 47-year-old woman had been treated for a carcinoid 10 years earlier and had received axillar irradiation. At presentation she suffered from weakness of the biceps brachii and was experiencing pain radiating from the axilla into the forearm and thumb. MR scans of the brachial plexus were negative and her symptoms were primarily considered to stem from a postradiation brachial plexopathy, Because of increasing pain, the brachial plexus was explored and a metastasis in the left musculocutaneous nerve was resected. Several months later, numbness and pain appeared in the ulnar nerve and another intrafascicular metastasis in the ulnar nerve was discovered. Resection with preservation of remaining fascicles was performed. This rare case report demonstrates that multiple mononeuropathies, resembling multiplex neuropathy, may be caused by intranerval metastasis.

Trigeminal sensory neuropathy: a study of 35 cases

OBJECTIVE

Trigeminal sensory neuropathy includes a wide variety of conditions sharing a common symptom described as sensory disturbance of the face--usually numbness.

STUDY DESIGN

This 10-year retrospective study included 35 patients referred for investigation of trigeminal sensory neuropathy.

RESULTS

The most common causes of trigeminal sensory neuropathy were nonneoplastic cerebral disorders, mainly represented by multiple sclerosis and idiopathic trigeminal sensory neuropathy. Furthermore, when only mandibular trigeminal sensory neuropathy was considered, metastatic neoplasia was the most frequent cause, often afflicting men over the age of 60 years.

CONCLUSIONS

This overview will orient clinicians in their diagnosis when they are faced with patients consulting for trigeminal sensory neuropathy.

Desmoplastic malignant melanoma presenting as a lung mass

A case of metastatic desmoplastic malignant melanoma is reported. The patient presented initially with a lung mass and subsequently developed facial swelling and numbness secondary to tumor involvement of the maxillary division of the trigeminal nerve. The pleomorphism, histochemistry, and schwannoid differentiation of these tumors is discussed.