Resident Physician Houston Methodist Hospital Houston, Texas, United States
Introduction: 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.
Methods: We describe an illustrative case of a male patient presenting with painful femoral mononeuropathy. Further workup revealed metastatic melanoma, including a solid metastasis directly to the femoral nerve.
Results: We believe our patient experienced a rare intraneural metastasis of melanoma to the femoral nerve, evidenced by the intrinsic T1 hyperintensity of the femoral nerve on MRI, indicating melanin deposition within the nerve, and the absence of adjacent lymphatic involvement. It was this focal metastasis that led to the patient’s clinical presentation and diagnostic workup.
Conclusion : Isolated mononeuropathies are abundantly encountered in clinical practice. However, in a patient with a history of recurrent skin lesions, an isolated mononeuropathy may be indicative of something far more sinister. The practitioner must harbor a high index of suspicion for malignancy in such instances. In our case, the patient was swiftly referred for biopsy and began treatment within six weeks.
