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Imaging of Metastatic Malignant Melanoma to the Head: Self-Assessment Module

¹ All authors: Department of Radiology, Emory University School of Medicine, B-115, 1364 Clifton Rd. NE, Atlanta, GA 30322.

Received September 11, 2007; accepted after revision April 25, 2008.

 
Address correspondence to A. Jayashankar (ajayash{at}emory.edu).

Abstract

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The educational objectives for this self-assessment module on the imaging of metastatic malignant melanoma to the head are for the participant to exercise, self-assess, and improve his or her understanding of the features used to differentiate hemorrhagic neoplasms from benign nonneoplastic hematomas on MRI and to gain familiarity with the varied appearances of melanoma metastases to the head.

Keywords: hemorrhagic neoplasms • intracranial hemorrhage • intracranial metastases • metastatic melanoma • MRI

INTRODUCTION

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This self-assessment module has an educational component and a self-assessment component. The educational component consists of three required articles that the participant should read and two recommended articles that may provide additional information and perspective. The self-assessment component consists of five multiple-choice questions with solutions. All of these materials are available on the ARRS Website (www.arrs.org). To claim CME and SAM credit, each participant must enter his or her responses to the questions online.

EDUCATIONAL OBJECTIVES

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By completing this educational activity, the participant will:

1. Exercise, self-assess, and improve his or her understanding of the MRI features used to attempt to differentiate hemorrhagic neoplasms from nonneoplastic hematomas.
   
2. Gain familiarity with the varied appearances of melanoma metastases to the head.
   
3. Improve his or her understanding of the current concepts in the imaging of intracranial metastatic melanoma.
   

REQUIRED READING

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(available at www.arrs.org)

1. Escott EJ. A variety of appearances of malignant melanoma in the head: a review. RadioGraphics 2001; 21: 625–639
   
2. Destian S, Sze G, Krol G, Zimmerman RD, Deck MD. MR imaging of hemorrhagic intracranial neoplasms. AJR 1989; 152:137–144
   
3. Jayashankar A, Sabourin SM, Mullins ME. AJR teaching file: acute onset headache. AJR 2008; 191[suppl]:S25–S27
   

RECOMMENDED READING

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1. Isiklar I, Leeds NE, Fuller GN, Kumar AJ. Intracranial metastatic melanoma: correlation between MR imaging characteristics and melanin content. AJR 1995; 165: 1503–1512
   
2. Gaviani P, Mullins ME, Braga TA, et al. Improved detection of metastatic melanoma by T2*-weighted imaging. AJNR 2006; 27:605–608
   

INSTRUCTIONS

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1. Complete the required reading.
   
2. Visit www.arrs.org and select Publications/Journals/SAM Articles from the left-hand menu bar.
   
3. Using your member login, order the online SAM as directed.
   
4. Follow the online instructions for entering your responses to the self-assessment questions and complete the test by answering the questions online.
   

QUESTION 1 Which of the following primary neoplasms is NOT typically associated with hemorrhagic brain metastases? Lung carcinoma. Prostate carcinoma. Melanoma. Thyroid carcinoma. Choriocarcinoma. QUESTION 2 Hemorrhagic neoplasms constitute approximately what percentage of intraparenchymal hematomas? 15%. 30%. 50%. 80%. 90%. QUESTION 3 Which of the following statements regarding the MRI features of hemorrhagic neoplasms as compared with nonneoplastic intraparenchymal hematomas is FALSE? Hemorrhagic neoplasms are more likely to show an incomplete hemosiderin rim than nonneoplastic hematomas. Hemorrhagic neoplasms are more likely to exhibit prolonged T2 hypointensity than nonneoplastic hematomas. Hemorrhagic neoplasms are more likely to be associated with persistent edema than nonneoplastic hematomas. Hemorrhagic neoplasms are more likely to show heterogeneous signal intensity than nonneoplastic hematomas. Hemorrhagic neoplasms are more likely to show methemoglobin formation initially at the periphery than nonneoplastic hematomas.

 

Solution to Question 1
Hemorrhagic brain neoplasms include both primary brain tumors and metastases. A hemorrhagic neoplasm is far more likely to be metastatic than primary [1]. Metastases that are most likely to hemorrhage include lung, breast, thyroid, renal cell, choriocarcinoma, and malignant melanoma [1]. Options A, C, D, and E are not the best responses. Metastases to the brain from prostate cancer are rare and are not typically associated with hemorrhage. Option B is the best response.

QUESTION 4 Which structure is most commonly involved by melanoma that metastasizes to the head? Brain. Meninges. Orbit. Internal auditory canal. Nasopharynx. QUESTION 5 The melanotic imaging pattern of metastatic melanoma is most typically associated with which of the following signal characteristics? T1 hyperintensity, T2 hyperintensity. T1 hyperintensity, T2 hypointensity. T1 hypointensity, T2 hyperintensity. T1 hypointensity, T2 hypointensity. T1 hypointensity, T2* hypointensity.

 

Solution to Question 2
Hemorrhagic neoplasms constitute approximately 1–14% of all intraparenchymal hematomas [2]. Option A is the best response.The differential diagnosis for the remainder of intraparenchymal hematomas includes primarily hypertensive hemorrhage, vascular anomalies (including arteriovenous malformation and cavernous malformation), hemorrhagic infarction, amyloid angiopathy, and trauma.

Solution to Question 3
Imaging features on MRI that suggest hemorrhagic neoplasm rather than benign intraparenchymal hematoma includes a heterogeneous or mixed intensity pattern (Option D); an incomplete hemosiderin rim (Option A); disproportionately large amount of edema compared with hematoma size, persistence of or increase in the edema over several days or weeks (Option C); persistence of T2 hypointensity beyond the expected time for a nonneoplastic hematoma (Option B); and initial appearance of T1 hyperintensity (subacute methemoglobin) centrally or eccentrically in the hematoma. Options A, B, C, and D, are not the best responses since they are true statements. In contrast, nonneoplastic hematomas usually show initial methemoglobin formation at the periphery of the hematoma [2, 3]. Although the precise mechanisms for the formation of methemoglobin have not been elucidated, it has been hypothesized that low oxygen tension levels favor the formation of methemoglobin. In a hemorrhagic neoplasm, low oxygen tension levels are found centrally, presumably in the necrotic portions of the tumor. For this reason, it is thought that methemoglobin formation initially occurs centrally (or eccentrically) in a hemorrhagic neoplasm rather than at the periphery [2]. Therefore, Option E, which is not true, is the best response.

Solution to Question 4
Melanoma metastatic to the head can involve virtually any intracranial or extracranial structure, including the meninges, orbit, nasopharynx, internal auditory canal, choroid plexus, bone, muscle, and meninges. However, the brain is the most common site of metastases to the head from melanoma [4]. Option A is the best response.Options B, C, D, and E are not the best responses.

Solution to Question 5
Two classic imaging patterns have been described for melanoma metastatic to the brain based on signal intensity characteristics. The melanotic form is characterized by T1 hyperintensity and T2 hypointensity. Option B is the best response. The amelanotic form is characterized by T1 hypointensity and T2 hyperintensity. Although some studies have shown high specificity of the melanotic imaging pattern for melanin-containing metastases [5], the association nevertheless remains controversial. The amelanotic imaging pattern is nonspecific. Gaviani et al. [6] studied the use of T2* images (susceptibility sequences) in the imaging of metastatic melanoma to the brain and reported a high specificity of combined T1 hyperintensity and T2* hypointensity for melanoma metastases. The classically described melanotic pattern, however, is based on the T1 and T2 signal characteristics only. Options A, C, D, and E are not the best responses.

References

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1. Mandybur TI. Intracranial hemorrhage caused by metastatic tumors. Neurology 1977;27 : 650–655[Abstract/Free Full Text]
2. Destian S, Sze G, Krol G, Zimmerman RD, Deck MD. MR imaging of hemorrhagic intracranial neoplasms. AJR1989; 152:137 –144[Abstract/Free Full Text]
3. Atlas SW, Grossman RI, Gomori JM, et al. Hemorrhagic intracranial malignant neoplasms: spin-echo MR imaging. Radiology1987; 164:71 –77[Abstract/Free Full Text]
4. Escott EJ. A variety of appearances of malignant melanoma in the head: a review. RadioGraphics 2001;21 : 625–639[Abstract/Free Full Text]
5. Isiklar I, Leeds NE, Fuller GN, Kumar AJ. Intracranial metastatic melanoma: correlation between MR imaging characteristics and melanin content. AJR 1995; 165:1503 –1512[Abstract/Free Full Text]
6. Gaviani P, Mullins ME, Braga TA, et al. Improved detection of metastatic melanoma by T2*-weighted imaging. AJNR2006; 27:605 –608[Abstract/Free Full Text]

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This Article Abstract Full Text (PDF) CME/SAM Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Jayashankar, A. Articles by Mullins, M. E. Search for Related Content PubMed PubMed Citation Articles by Jayashankar, A. Articles by Mullins, M. E. Social Bookmarking                      What's this? Hotlight (NEW!) What's Hotlight?