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Journey through Metastatic Melanoma of the Central Nervous

System

J Nair, A Alamer, S Saif, C Torres, J Chankowsky, R del carpio

Learning ObjectivesTo describe the conventional magnetic resonance imaging (MRI) findings of Metastatic CNS melanoma, especially the signal characteristics based on their contents.

Identify different imaging patterns of CNS melanoma and their anatomic sites of involvement.

Discuss the post-treatment imaging pattern.

BackgroundMalignant melanoma represents the third most common cause for cerebral metastasis after breast and lung cancer. Central nervous system (CNS) metastasis occur in 10 to 40 % of patients with melanoma.

Most of the symptoms of CNS melanoma metastasis are non-specific and depend on the location of the lesion.

The majority of patients have multiple lesions, supratentorial being more common than infratentorial. Similar to other metastasis, they are predominantly located at the gray-white matter junction with surrounding significant vasogenic edema. Homogenous enhancement is seen on post contrast images.

Melanoma metastases can be divided into:

1) Melanotic : Containing greater than 10% melanotic cells on histopathology.

2) Amelanotic : Containing less than 10% melanotic cells.

However, this pattern approach is considered to be oversimplified as the amount of melanin-containing cells in metastases is extremely variable. It has been postulated that intralesional hemorrhage plays a greater role in influencing the imaging appearance of melanoma than the melanin content.

Background

Our ApproachAn extensive search was made for melanoma of the Central nervous system at our institution, from the database available on PACS from 2005 to 2014. All cases were evaluated and based on the findings, the poster has been designed.

Our MRI protocol Included:

• Sagittal T1W 5mm thickness.

• Axial T1W, T2W, FLAIR and DWI (including ADC map) 5mm thickness.

• Coronal T2W and GRE 5mm thickness.

• Post-gadolinium injection; Axial & Coronal T1W (5mm) and/or Axial T1W 3D FSPGR 1mm thickness. 

Imaging FindingsMRI features of Metastatic Melanoma:

1. Intracranial disease:

Patterns:

A. Melanotic : Hyper intense relative to the cortex on T1-weighted images and hypo intense relative to the cortex on T2-weighted images with post- contrast enhancement. (Fig 1), (Fig 2)

B. Amelanotic : Hypo intense on T1-weighted images and iso- to hyper intense relative to the cortex on T2-weighted images with post- contrast enhancement. (Fig 3), (Fig 4)

C. Hemorrhagic : The signal intensity on T1WI and T2WI depends on the stage of hemorrhage stage; acute, early subacute, late subacute or chronic. (Fig 5)

D. Cystic : Not commonly described. The cystic portion has variable signal, usually hypo intense on T1WI and hyper intense on T2WI. (Fig 6)

E. Subependymal : Nodular periventicular, ribbonlike signal with marked enhancement. (Fig 7)

F. Perineural/leptomeningeal : Sugar-coating of the pial surface or along the cranial nerves. (Fig 8), (Fig 9)

Imaging Findings

2. Extracranial:

A. Spine:

I. Spinal Cord, Cauda equina and nerve roots : Well defined enhancing leptomeningeal nodules of the cord and thick enhancing sheets of metastatic deposits along the conus medullaris, cauda equina and nerve roots. (Fig 10) (Fig 11)

II. Vertebral bodies: Extensive anterior and posterior element involvement with multilevel collapse of vertebral bodies. (Fig 12)

Imaging Findings

B. Orbits : Involves the eye globes, extra ocular muscles, lacrimal glands and/or bony orbit. (Fig 13)

C. Muscles : Lesions show restricted diffusion signal, enhancement and possible adjacent bone erosion/infiltration. (Fig 14)

D. Parotid glands : Involvement can be unilateral or bilateral. (Fig 15)

E. Scalp and neck muscles : Scattered well defined enhancing soft tissue metastatic lesion. (Fig 16)

Imaging Findings

3. Post therapeutic MR features:

Treatment options:

Surgery.

Chemotherapy.

Radiation therapy.

Biological therapy.

Targeted therapy.

Imaging: In addition to the reduction in size of the lesions and surrounding edema, lesions are relatively hypo intense on both T1 and T2 with peripheral hemosiderin deposition on T2WI. Minimal or no post contrast enhancement noted. (Fig. 17)

Differential DiagnosisAnaplastic lung carcinoma.

Thyroid carcinoma.

Choriocarcinoma.

Renal Cell carcinoma.

ConclusionMalignant melanoma has a wide spectrum of appearance with involvement of the intra and extra cranial structures.

Although brain is the most common site of metastasis in the head and neck, metastatic melanoma can involve essentially any structure including the spinal cord.

This pictorial review from our institution will familiarize radiologists with typical and atypical imaging features and locations of malignant melanoma on MRI when screening patients.

References Goulart CR, Mattei TA, Ramina R. Cerebral Melanoma Metastases: A Critical Review on Diagnostic Methods and Therapeutic Options. ISRN Surgery 2011;2011:276908.  

Smith, AB, Rushing, EJ, and Smirniotopoulos, JG. Pigmented lesions of the central nervous system: radiologic-pathologic correlation. Radiographics. 2009; 29: 1503–1524.

Escott EJ. A variety of appearances of malignant melanoma in the head: a review. RadioGraphics 2001;21(3):625–639.

 Isiklar I, Leeds NE, Fuller GN, Kumar AJ. Intracranial metastatic melanoma: correlation between MR imaging characteristics and melanin content. AJR Am J Roentgenol 1995;165(6):1503–1512.

Journey through Metastatic Melanoma of the Central Nervous

System

J Nair, A Alameer, S Saif, C Torres, J Chankowsky, R del carpio