Primary Malignant Melanoma of the Cervical Spinal ... - E-kjs.org

Primary Malignant Melanoma of the Cervical Spinal Nerve Root
Fig. 2. Malignant melanoma composed of highly anaplastic cells with hyperchromaic nuclei, abundant
eosinophilic cytoplasm, and melanin pigments (×200) (A). Positive findings for vimentin, s-100 protein,
and HMB-45 (×200) (B).
scattered low signal intensity lesions within the mass were
identified on the T2 weighted image; these were thought to be
due to the presence of melanin, later (Fig. 1). Preoperative clini
cal and radiographic diagnosis was nerve sheath tumor such as
neurofibroma or schwannoma. An operation using the anterolateral
approach at left supraclavicular area between the carotid
sheath and sternocleidomastoid muscle was performed. The
bulk of the mass was removed. At surgery an encapsulated pitch
black mass was found. It was large, firmly attached to brachial
plexus and C6-7 neural foramen. Pathological examination confirmed
the diagnosis of malignant melanoma. It is composed of
highly anaplastic cells with hyperchromaic nuclei, abundant
eosinophilic cytoplasm, and melanin pigments. And it presented
positive findings for vimentin, s-100 protein, and HMB-45
(Fig. 2). The tumor had a high Ki-67 labeling index (35%). The
patient’s symptoms improved totally after the operation. The
patient wanted to transfer to other hospital for more thorough
evaluation on post-op 11th day. So we could not proceed adjuvant
therapy and follow-up observation.
DISCUSSION
The cell of origin of melanotic tumors involving the spinal
nerve root can be either a melanocyte, a Schwann cell, or an
uncharacterized cell type 11) . Melanocytes are melanin-producing
cells that arise from the neural crest during embryogenesis, and
migrate to the skin, mucous membranes, and central nervous
system. Tumors arising from melanocytic cells (primary and
metastatic melanoma) and Schwann cells (melanotic nerve sheath
tumors) have a common embryological origin in the neural
crest 8,11) .
Because of rarity of primary melanoma in spinal nerve root,
the diagnosis can be difficult. Radiological studies may not be
specific. Magnetic resonance imaging may offer some indication
of a melanotic lesion, melanin can show a hyperintense
or isointense signal on T1 weighted images and decreased signal
on T2 weighted images 7,9,12) .
The pathological differential diagnosis of primary melanoma
includes metastatic melanoma, melanocytoma, melanotic schwannoma,
and melanotic clear-cell sarcoma. Melanocytoma lacks
anaplastic features such as necrosis, significant mitotic activity,
and pleomorphism, in contrast with primary melanoma. The
characteristics of primary malignant melanomas are considerable,
including nuclear pleomorphisms leading to large and bizarreshaped
tumor cells with multinucleated giant cells 13) . A high
mitotic rate, coagulative necrosis and hemorrhage are also commonly
found in primary malignant melanoma 1,13) . Immunohistochemical
staining is also helpful for differentiation. Significant
s-100 protein expression without the expression of epithelial
membrane antigen supports the diagnosis of a schwannoma
or melanoma 5,13) . Negative immunoreactivity for Leu-7
rules out schwannoma whereas the detection of HMB-45 favors
the diagnosis of a melanocytic tumor 5,13) .
Schneider et al. 11) reported a case of primary melanoma arising
from the L3 spinal nerve root that was treated by wide
en-bloc resection. Skarli et al. 12) reported a similar case of primary
malignant melanoma arising in a cervical spinal nerve
root that did not recur or metastasize over 3 years without adjuvant
chemotherapy or radiation therapy after surgical operation.
Also Kwon et al. 4) reported a case of primary malignant melanoma
of the C7 nerve root in 2004 that was treated with adjuvant
radiation therapy.
Because of the rarity of these lesions, the prognosis and proper
adjuvant therapy (chemotherapy, radiotherapy) have not been
established yet.
It is important to differentiate primary melanoma from metastasis.
The prognosis for patients with metastatic melanoma to
central nervous system is dismal, with a life expectancy of less
than 1 year in most studies 2,4,10) . In contrast, primary melanoma
has long-term survival and better prognosis than metastatic lesion.
Kor J Spine 6(1) March 2009 41