Findings from CT, MRI, and PET/CT of a primary malignant melanoma arising in a spinal nerve root

Abstract

Primary spinal malignant melanoma is an extremely rare condition. We here describe a case of a 71-year-old Asian female presenting with left upper extremity tingling sensation. Computed tomography (CT) showed a homogeneously enhanced mass occupying the left neural foramen at the C6-7 level. Magnetic resonance imaging revealed enhanced mass in intra- and extradural space compressing the spinal cord at this level. It also widened the neural foramen mimicking neurofibroma or schwannoma. Partial resection of the mass was performed. Pathologic diagnosis of the mass was malignant melanoma. Postoperative whole body positron emission tomography/CT scan demonstrated an intense (18)F-FDG uptake at the residual mass site without abnormal uptake at other sites in the body.

Fig. 1

a Non-enhanced axial CT demonstrates a well-defined mass with neural foraminal widening at C6–7. The mass shows similar homogenous density, relative to the skeletal muscle. b Contrast-enhanced axial CT shows heterogeneous, well-enhanced mass at same levels. c Axial T1-weighted image shows a dumbbell-shaped, homogeneous mass with slight hyperintensity, compared with the spinal cord at the C6–7 level. d Axial T2-weighed MR images show a slightly hypointense mass with a dark signal portion at the anterolateral aspect of the mass. e Gadolinium-enhanced T1-weighted image show mild heterogeneous enhancement of the mass

Fig. 2

a H&E (×200) shows the tumor consisted of clusters of tumor cells with abundant eosinophilic, granular cytoplasm. The tumor cells had pleomorphic nuclei and prominent nucleoli. Melanin pigmentation was present. b HMB45 (×200) reveals that tumor cells showed positive reaction for HMB-45

Fig. 3

PET/CT results. a Transverse fused PET/CT image shows intense FDG uptake in the mass of the left neural foramen at the level of C6–7. b Coronal maximum intensity projection image demonstrates FDG uptake at the tumor site, without abnormal uptake at other sites in the body. Normal physiologic intense FDG activity is seen in the brain, myocardium, and bladder. Note also the focal high accumulation of FDG in the left thumb region of the site of FDG injection