MELANOMA

Introduction

• Demographics• Characteristics of metastases• Metastases to different systems

Melanoma

• Malignant neoplasm of melanocytes• Most frequently arises from skin• Caucasian females, age 30-50, pigmented

lesion, often on leg• RF- sun exposure• Dx. – biopsy• Depth of skin invasion at diagnosis

determines prognosis (Breslow, Clark)

Metastases

• 64% with disseminated disease develop first metastasis within first year

• Early melanoma can be successfully treated buts mets have poor prognosis

• Rx for mets include surgery, chemotherapy, Dxt., immunotherapy

• First mets to regional LN and skin

Radiological features

• Typical of melanoma– Associated with melanin content– Hypervascularity– Tendency to cystic and haemorrhagic change– Hyperdense on CT– MRI- High on T1, low on T2

• Non specific findings common to all cancers

Central Nervous system

• 3rd most frequent cause of brain mets• Often cortico-medullary and multiple • CT- hyperdense (related to melanin),

surrounded by oedema. Haemorrhage (19%), meningeal spread (11%)

• MRI – High signal on T1 low on T2• Spinal mets – discrete or diffuse, intra or

extra medullary

CT – brain mets

MRI – pre/post gad

Pre and post gad T1 weighted MRI

Sphenoid met –T1 MRI

Pre and post gad T1 MRI

Head and Neck

• Most frequent intra-occular tumour in adults

• Variable size and shape, often associated with retinal detachment

• USS – usually homogenously echogenic, cystic change with necrosis / haemorrhage

• Colour doppler – tumour vascularity, low resistance flow pattern,

Head and Neck

• USS –assess extra occular soft tissues• CT and MRI for extra scleral invasion• MRI –High signal on T1 low on T2 (c.f vitreous)

for intra occular tumours• Scleral invasion – thinning of dark scleral band,

increased scleral signal, contrast enhancement• Extra scleral invasion – discontinuity of sclera,

soft tissue mass (different signal to fat)• Lymphadenopthy, bony mets, parotid glands

Choroidal melanoma and retinal detachment

Chest

• Multiple pulmonary nodules on CXR• Less commonly solitary nodule,

lymphadenopathy and rarely miliary mets, pleural effusion

• Occasionally endobronchial and cardiac mets (difficult to diagnose on imaging)

• CT for staging• PET increases sensitivity

Mets

Miliary mets

Musculoskeletal

• Bony mets in 23% of a series of 110• Most frequently spine• Majority osteolytic. Occasionally bony

expansion, subarticular location, sclerosis, sclerotic rim

• Pathological #s through mets are common• Bone scintigraphy more sensitive than

plain film

Musculoskeletal

• Cutaneous and subcutaneous mets are relatively common

• CT-non specific soft tissue density nodules• USS- hypoechoic, smooth or lobulated

masses with distal acoustic enhancement, with internal arterial flow

• Skeletal muscle mets – High on T1 low on T2

Mets with pathological fracture

Abdominal wall metastasis

Left postero lateral abdo wall met

Right psoas met and subcutaneous deposit

Breast

• Melanoma 2nd most common primary to spread to breast after breast primaries

• Multiple well defined nodules, similar to benign disease

Breast mets

Gastrointestinal• Relatively uncommon• Mostly small bowel, also stomach• Polypoid lesions (63% of GI mets from

melanoma in one series)• Cavitating mass (25%), infiltrative mass (16%),

target lesion (9%)• CT and SB follow through relatively inaccurate

(sensitivities 66 and 58 %)• Complicated by intussuseption, obstruction,

haemorrhage

Stomach met

Hepatobiliary

• Most frequent site of visceral involvement from melanoma

• Hypervascular• Portal venous and unenhanced or arterial

phase scans• Typical MRI melanoma characteristics

(high T1) in 23%. More commonly low T1, iso/high T2

• USS – hypoechoic lesion, fluid in 30%

Hepatobiliary

• Gall bladder involvement in 15 % (post mortem series)

• Occasionally obstructive jaundice• Splenic mets in 35% at autopsy

Hepatic and splenic metastases

Biliary obstruction

Urogenital tract

• 3rd most frequent tumour to metastasize to kidney (after lung and breast)

• Renal parenchyma and perinephric fat• Adrenal mets (only lung camcer and renal

cell carcinoma are more frquent causes)• Reproductive organs occasionally involved• MRI useful in characterising adrenal mets

(chemical shift, in and opposed)

Adrenal and subcutaneous metastases

Renal metastasis

Conclusion

• Malignant melanoma, once disseminated is extremely aggressive

• Typical radiological findings relate to melanin content, hypervascularity, cystic and haemorrhagic change

• CT – hyperdense, can be cystic, haemorrhagic

• MRI typically high on T1 low on T2 • Atypical appearances, all systems affected