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| LETTER TO EDITOR |
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| Year : 2017 | Volume
: 65
| Issue : 6 | Page : 1427-1428 |
Advanced magnetic resonance imaging in the diagnosis of primary intracranial malignant melanoma
A Saranya1, Rajeswaran Rangasami1, Anupama Chandrasekharan1, Ganesh Krishnamurthy2, Rajendran Swaminathan3
1 Department of Radiology and Imaging Sciences, Sri Ramachandra University, Chennai, Tamil Nadu, India
2 Department of Neurosurgery, Sri Ramachandra University, Chennai, Tamil Nadu, India
3 Department of Pathology, Sri Ramachandra University, Chennai, Tamil Nadu, India
| Date of Web Publication | 10-Nov-2017 |
Correspondence Address:
Dr. Rajeswaran Rangasami
Department of Radiology and Imaging Sciences, Sri Ramachandra University, Chennai - 600 116, Tamil Nadu
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0028-3886.217953
How to cite this article:
Saranya A, Rangasami R, Chandrasekharan A, Krishnamurthy G, Swaminathan R. Advanced magnetic resonance imaging in the diagnosis of primary intracranial malignant melanoma. Neurol India 2017;65:1427-8 |
How to cite this URL:
Saranya A, Rangasami R, Chandrasekharan A, Krishnamurthy G, Swaminathan R. Advanced magnetic resonance imaging in the diagnosis of primary intracranial malignant melanoma. Neurol India [serial online] 2017 [cited 2023 Jun 5];65:1427-8. Available from: https://www.neurologyindia.com/text.asp?2017/65/6/1427/217953 |
Sir,
Melanoma develops from the pigment-containing cells, melanocytes, and typically occurs in the skin. Primary malignant melanoma of the central nervous system (CNS) is rare, accounting for 1% of all melanomas.[1] Most of the melanomatous tumors occur in the meninges covering the base of the brain or spinal cord.[2] To the best of our knowledge, only one case of cavernous sinus melanocytoma has been reported so far.[3]
An 18-year old male patient presented with complaints of headache, multiple episodes of vomiting, difficulty in speech, and right hemiparesis of 3-day duration. Nervous system examination revealed bilateral papilledema, reduced bulk of left masseter and temporalis muscles, decreased sensation over left side of the face, and grade IV weakness of right upper and lower limbs. Magnetic resonance (MR) examination of the brain revealed a dumbbell shaped mass of size 4.0 × 3.1 × 3.2cm with solid and cystic components in the left cavernous sinus and extending into the posterior fossa. The lesion appeared predominantly mildly hyperintense on T1 and T2-weighted images [Figure 1]a and [Figure 1]b. Hemorrhage was seen in the posterior aspect of the mass [Figure 1]c. The posterior component was seen to extend upto the left cerebellopotine angle causing compression on the brainstem. MR perfusion (using T2 dynamic susceptibility contrast-enhanced perfusion technique) revealed that relative cerebral blood volume of the tumor was 2.4 times that of the normal brain parenchyma [Figure 1]d. Heterogeneous enhancement was seen following contrast administration [Figure 1]e and [Figure 1]f. Initial MR spectroscopy (MRS) of the tumor was interpreted as increased choline (Cho) and reduced N-acety aspartate (NAA) with Cho/NAA ratio of 1.13 with a large lipid lactate peak (1.32ppm). Retrospective re-analysis revealed additional peaks corresponding to taurine (3.4ppm), lysine (1.73ppm), and glutamine–glutamate (2.4ppm) [Figure 2]a and [Figure 2]b. The left trigeminal nerve was not seen separately from the mass. An imaging diagnosis of Vth nerve schwannoma was made. | Figure 1: (a) Axial T1-; and, (b) T2-weighted MR images show a mass in the left cavernous sinus mildly hyperintense to gray matter (arrow). Patchy bright hyperintense areas are seen in the anterior aspect of the mass (open arrow). (c) Axial gradient images show blooming in the posterior part of the mass (broken arrow). (d) Axial perfusion image shows increased perfusion (arrow head). (e and f) Postcontrast T1 images show a strong enhancement in the mass (curved arrow)
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 | Figure 2: (a and b) MR spectroscopy with voxel within the mass shows amino acid peaks (arrows), a large lipid lactate peak besides a cho/NAA ratio of 1.13
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At surgery, the covering of the lesion had blackish discoloration. Owing to extensive vascularity and adherence to brainstem, only partial excision and internal decompression of the tumor was done. On microscopy, the cells showed brown-black pigmentation. The tumor cells showed strong positivity for HMB45 and S100 confirming the diagnosis of melanoma [Figure 3]. Patient improved symptomatically after surgery and was referred for radiotherapy. | Figure 3: Histopathology sections showing features of a melanoma. (a) The tumor cells showing positivity for HMB-45 (×100). (b) Tumor cells showing cytoplasmic positivity for S100 (×100)
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Melanocytes are of neural crest origin, and during development they migrate to the skin, uvea, mucous membranes, and leptomeninges. On rare occasions, few melanocytes that remain in the central nervous system (CNS) can become neoplastic.[4] Majority of melanocytic lesions in the brain are metastatic. According to Hayward's criteria, a solitary lesion in the leptomeninges, the pineal gland, or the intramedullary region is more likely to be a primary CNS melanoma, provided that there is no melanoma elsewhere in the body.[5] The World Health Organization (WHO) categorizes primary CNS melanocytic lesions into diffuse melanocytosis, melanocytoma, and malignant melanoma.[6] Diffuse leptomeningeal melanocytosis occurs in the setting of neurocutaneous melanosis syndrome and is characterized by leptomeningeal thickening or nodularity.[7] Meningeal melanocytoma is a benign low-grade tumor and the common locations are the cervical/thoracic spine, posterior fossa, Meckel's cave, and cerebellopontine angle. Primary malignant melanoma is a rare aggressive dural-based tumor commonly occurring in the cerebellopontine angle, pineal gland, cerebrum, and spine.[8]
Clinically, the patients with CNS melanoma can present with features of raised intracranial tension, cranial nerve palsies, neurological deficits, seizures, or subarachnoid hemorrhage.[7] On computed tomography (CT), melanomatous lesions appear hyperdense and show a homogenous contrast enhancement.[6],[7],[8],[9],[10] On MR imaging, these lesions show an increased signal on T1- and decreased signal on T2-weighted images due to the presence of melanin. On perfusion imaging, these lesions show hyperperfusion.[6] The MRS findings described in extracranial melanomas are elevated choline, lactate, and amino acids such as taurine, alanine, lysine, and glutamate.[10] The differential diagnoses are other pigmented tumors such as pigmented schwannoma and meningioma.
On macroscopy, melanocytomas and melanomas appear as reddish brown-to-black masses. On sections stained with hematoxylin and eosin, melanocytomas show sheets of well-differentiated epitheloid melanocytes having round-to-oval nuclei with finely dispersed chromatin, occasional single eosinophilic nucleoli, and moderate amount of cytoplasm with abundant granular melanin pigment.[9] On immunohistochemisty, the tumor cells show diffuse strong HMB45 and S-100 immunopositivity. Surgical excision is the treatment of choice for primary melanoma. Postoperative radiotherapy and chemotherapy help in prolonging remission.[8],[9],[10] In conclusion, primary malignant melanomas of CNS are extremely rare tumors and show pathognomonic imaging features such as increased perfusion, and amino acid peaks representing taurine, lysine, and glutamine on MRS.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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| 3. | Faro SH, Koenigsberg RA, Turtz AR, Croul SE. Melanocytoma of the cavernous sinus: CT and MR findings. AJNR Am J Neuroradiol1996;17:1087-90. |
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| 6. | Balakrishnan R, Porag R, Asif DS, Satter AM, Taufiq M, Gaddam SS. Primary intracranial melanoma with early leptomeningeal spread: A case report and treatment options available. Case Rep Oncol Med 2015;2015:293802. |
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| 8. | Jaiswal S, Vij M, Tungria A, Jaiswal AK, Srivastava AK, Behari S. Primary melanocytic tumors of the central nervous system: A neuroradiological and clinicopathology study of five cases and brief review of literature. Neurol India 2011;59:413-9. [ PUBMED] [Full text] |
| 9. | Shinde SV, Shenoy AS, Savant HV, Balasubramaniam SB. Coexistent intracerebral metastatic melanoma and meningioma. Neurol India 2017;65:110-2. [ PUBMED] [Full text] |
| 10. | Bourne RM, Stanwell P, Stretch JR, Scolyer RA, Thompson JF, Mountford CE, et al. In vivo and ex vivo proton MR spectroscopy of primary and secondary melanoma. Eur J Radiol 2005;53:506-13. |
[Figure 1], [Figure 2], [Figure 3]
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