Metastasis from the extracranial primary melanoma
is more frequent to appear in the brain and is the third
most common site of intracranial metastasis after carcinoma
of breast and lung [
1]. However, primary intracranial
melanomas are exceptionally rare presenting either
solitary or of diffuse variety [
2]. Our case was a primary
solitary melanoma presented in posterior fossa.
Primary melanocytic neoplasms are rare lesions
arising from normally occurring leptomeningeal melanocytes
[3]. Current embryologic data suggests a common
origin of melanocytes originating from the neural crest
elements normally found within the basal layer of the
epidermis and the leptomeninges covering the base of
the brain and the brain stem [4-6]. Thus, these cells
commonly cluster in the pons, cerebellum, cerebral
peduncles, medulla, interpeduncular fossa, and inferior
surfaces of the frontal, temporal, and occipital lobes
[5,7,8]. These neoplasms are generally divided into three
main types, including diffuse melanosis, meningeal
melanocytoma, and primary malignant melanoma. The
prognosis in case of solitary primary intracranial melanomas
depends upon the degree of mitosis, leptomeningeal
dissemination, extent of surgical excision and
location of the tumor [1]. Diffuse leptomeningeal melanomas
mainly appear in children and may be part of
neuro-cutaneous melanosis complex or phakomas [9].
These may present with features of raised intracranial
pressure, cranial nerve palsies and meningism [1]. But
focal melanomas like our case present as leptomeningeal
or dural based neoplasms and are more common in
adults.
Yamane et al. [10] stated a major difference of mean
survival between solitary diffuse leptomeningeal melanoma
cases with 20.7 months and 6.7 months; respectively.
Radical tumor resection and use of aggressive
whole brain irradiation have been recommended [1,10].
The prognosis and long term survival interval were
reported to be longer (19.6±2.3 months) with a radical
tumor resection and shorter (9.3+2.4 months) with only
a biopsy or partial tumor excision [1]. Radical approach in our case with gross total tumor resection followed by
external beam radiotherapy to posterior fossa up to 60
Gy and adjuvant chemotherapy established a surprising
disease-free duration for 17 years.
Metastasis from primary intracranial melanomas to
lungs, spleen, pancreas and kidneys although rare, have
been reported in the literature, while we have not observed
any systemic metastasis in long follow up of our
case [11]. However, a second primary melanoma in temporoparietal region emerged 17 years after initial
posterior fossa melanoma and developed to disseminate
diffusely even after gross total resection.
In conclusion, aggressive adjuvant treatment including
localized radiotherapy and/or chemotherapy after gross
total resection of a solitary primary melanoma seems to
be a constructive way in decision making of proper
management in shaping the emerging literature.
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