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Liver Mets 1

Differential Diagnosis

  • Colon
  • Breast
  • Lung
  • Pancreas
  • Stomach

    Melanin = Melanoma ( high T1 ) Mucin = Mucinous pancreas / colon / ovaries Haemorrhage = rare.

Mets are all BS mostly arterial whilst parenchyma is 25% .

Hypervascular

  • NET ( carcinoid, insulinoma, phaeo )
  • Thyroid
  • Renal (RCC)
  • Breast ( small and odd )
  • Melanoma
  • Sarcoma

Hypovascular

  • Adenocarcinoma ( GI, pancreas and lungs )
  • Breast Ca
  • Squamous Cell Carcinoma ( ENT, Lung, Anus )
  • Lymphoma

Technique

Suggest do initial staging of arterial and portal. - Detect arterial mets
- Differential benign lesions better.

Then suggest single phase if ok.

Primovist can have uptake into mets due to persistent vascular signal but also uptake into fibrous scars.

Treatment and Treatment Effects

Radiofrequency Ablation (RFA)

Can be done for mets generally <3cm, 1-3 in number (<5), NOT next to major bile ducts.

Post - RFA

  1. Non-enhancing area = Coagulation Necrosis
    • should have 0.5cm margin.
    • can have rim enhancement due to phys reaction.
    • this phase is over by approx 1 month.
  2. Usually this lesion will shrink over time.
  3. Concerning features for recurrence
    • Ablation is smaller than initial lesion.
    • Non rim-like enhancement.
    • Increasing size of enhancement.
    • New enhancement after 1 month.

Persistence of lesion and round shape and low attenuation suggests biloma.

Tumour Resection

  • Can get fluid collection +/- gas in bile ducts etc.
  • Expect hypertrophy of the normal structures
  • Tumour recurrence = Solid enhancing mass.

Differential Diagnosis

FNH

  • Central scar = enhances in equilibrium phase (both CT & MR) and ^^T2.
    • but can be seen in breast Ca Mets.
  • Primovist = Signal in delayed phase (mets are low signal)

Haemangioma

  • Higher T2 and usually centripetal enhancement.
  • Small ones are tricky and tend to be hypervascular.
  • Primovist is not helpful as get 'pseudo-washout'.

Splenic Mets

Uncommon (1-3% in PMs). Thought to be due to lack of afferent lymph vessels.
Very rare as the only site of metastatic disease.

Usual splenic diseases

  • NHL/HD.
  • Infection.
  • Storage Disorders.
  • Congestion.
  • Extramedullary haematopoiesis.

Splenic Mets

  • Melanoma
  • Breast
  • Lung
  • Colorectal
  • Ovary
  • Stomach

Splenic Implants

  • Usually Peritoneal carcinomatosis
    • Ovary
    • Pancreas
    • Gastric
    • Colorectal

Splenic lesion Differential

  • Haemangioma
  • Lymphangioma
  • Hamartoma
  • Littoral Cell Angioma
  • Cysts (False, Epidermoid, Parasitic)

Adrenal Mets & Other Stuff.

4th most common but freq asymptomatic esp in elderly.
Hypoadrenalism is rare and usually only with bilateral and large in young people.

Causes

Breast (30-40% will get them)
Lung (30-40% will get them)
Melanoma (50%) GI (10%)
Renal (10%)

90% are carcinomas (Rest are melanomas, NHL, sarcomas)

Differentials

  1. Adenoma / Fat-poor adenoma
    • 10% of normal on CT. 0.2% at 20yo, 7% at 70yo.
    • ~ Obesity, DM, Age, Female
  2. Adrenal Cyst
    • F>M
    • Can look a bit confusing.
  3. Primary Adrenal Carcinoma
    • Rare & very malignant.
    • >6cm, Hetero, Ca2+, necrotic.
  4. Myelolipoma
    • Fat and haematopoietic tissue.
    • Fat should be the same attenuation as the subcutaneous fat.

Radiological Features

Normal limbs <5mm
Mets = Homogeneous if <3cm, but heterogeneous >3cm.
Hypo T1 (vs Liver) and Hyper T2 (can be +++ and thus look like phaeo)

Size
>3cm = 90-95% are malignant.
\<3cm = 85% are benign.

Bilateral Not confirmatory as bilateral adenomas are not uncommon.
And think of phaeo and TB as alternatives.

CT Criteria
Based on 2 concepts:
1) FAT CONTAINING = ADENOMA
though rare mets in an adenoma and fat containing RCC/HCC and liposarcoma

NCCT \<10HU = Adenoma (S/S = 74/96)

Also, HISTOGRAM ANALYSIS TECHNIQUE
- Draw circle over 2/3 of the area.
- See if / proportion of pixels are \< 0HU
- 88% of lipid poor adenoma ( ie standard HU >10HU ) have some negative HU pixels.
- 53% of adenomas on CECT have negative pixels vs 0% of mets.
- On NCCT >= 5% negative pixels S/S = 92/100

2) ENHANCEMENT CHARACTERISTICS
adenomas drain faster than mets

\[ Absolute Percent Washout=\frac{e-d}{e-u}x100 \]

e = attenuation at 60s post iv contrast
d = attenuation at 15mins delay.
u = attenuation on non-contrast.
Absolute 60% washout at 15% = 88/96 for adenoma.

$$ Relative Percent Washout=\frac{e-d}{e}x100 $$ Relative >40% is 96/100 for adenoma!

MR Imaging

Exploit presence of fat.

\[ Signal intensity index = \frac{SI in phase - SI out of phase}{SI in phase}x100 \]

Adenomas tend to be > 5%, whilst mets tend to be <5%. Also compare to the change in signal from the spleen.

  1. Sahdev A and Vinnicombe S. Husband & Resnek Imaging in Oncology. CRC Press 2020. ↩