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Lung Mets 1

Nodules

Are the most common general pattern of malignant infiltration into the chest.
Several specific patterns

Miliary Nodules

  • Thyroid
  • RCC
  • Melanoma

Ground Glass Nodule

  • Choriocarcinoma
  • Melanoma
  • RCC
  • Angiosarcoma
  • HL / NHL

Can be due to:

Focal interstitial infiltration.
Partial airspace filling by tumour.
Haemorrhage which mostly produces a halo.
Mucin-producing tumours (ie CRC). These tend to coalesce to produce consolidation.
Also can get diffuse multifocal lung adenoca (aka BACC) which does lepidic growth around alveolar walls and partial filling of airspaces.

Calcified Nodules

  • Osteo or chondrosarcoma.
  • Mucinous adenoCa.
  • Also Pap Thyroid Ca, Synovial cell sarcoma.
  • And treated metastases.

DD: Granuloma. Amyloid. Hamartoma.

Nodules with Branching Morphology.

Airways

  • Breast
  • Kidney
  • Colon
  • Lymphoma
  • Melanoma

Can be:

i. Trachea to Segmental Airway.
"Arborizing opacity" paralleling the vessels
+/- Collapse distally.

ii. Respiratory to Terminal Bronchiole.
Centrilobular opacity.
Tree-in-bud.

Vessels

  • Soft tissue Sarcoma
  • RCC
  • HCC
  • Melanoma

Tumour in the medium to small arteries

Producing branching lobular enlargement which can be smooth or beaded.
Can lead to peripheral infarction.

Can rarely be Tumour Venous Thrombosis
from either invasion of the LA or of invasion of the venous system.
Lead to Dilated PV with/without filling defects in the LA or venous system.
Mostly due to Squamous Cell Carcinoma or Sarcoma.

Cystic or Cavitating Nodules

  • Squamous Cell Carcinoma (of cervix, H+N)
  • Colorectal Carcinoma
  • Sarcoma
  • Urothelial Carcinoma
  • Lymphoma
    But also consider the non-neoplastics
  • GPA ( Wegeners )
  • Eosinophilic GPA ( Churg-Strauss )
  • Rh A
  • Amyloidosis
  • LCH ( 3-4 mm with thin walls )
  • INFECTION = Fungi, mycobacteria, septic emboli
  • OTHER = Tracheobronchial papillomatosis.

Cavitation and decreasing size suggests treatment response.

Reticular Pattern Disease.

Infiltration of tumour into interstitial components which are:

  1. Perihilar axial interstitium
  2. Centrilobular interstitium
  3. Subpleural interstitium
  4. Interlobular septa

Lymphangititis should leave the rest of the lung normal unlike ILD.

Lymphatic spread can be:

  1. via Pulmonary Arterial Mets:
    1. Breast
    2. GIT
    3. Melanoma
  2. via Direct Extension from hilar lymphadenopathy:
    1. HD
    2. NHL

Reticulonodular Disease

~ Lymphangitic tumour spread can cause a combined nodular and reticular pattern.

  1. Breast
  2. GIT
  3. Melanoma
  4. Lymphoma

Can emulate LIP = though these get parenchymal cysts.

Mixed, Airspace and Interstitial Disease

  1. Lymphoma ~ classic mix of patterns and nodules
  2. Invasive Mucinous AdenoCa & AdenoCa with papillary pattern ~ can mimic lobar pneumonia, though often have other clues such as nodules. Crazy paving and cysts within the consolidation are also described.
  3. Kaposi's Sarcoma. ~ common pattern is mediastinal and hilar lymphadenopathy with flame shaped lesions or nodules arise in thickened interstitium.

Pleural Disease

Metastatic disease can be effusions or thickening or nodularity.
25% of new pleural effusions on CXR = Ca. Though direct relationship to age and size.
50% of bilateral with normal heart size.

Effusions

  1. AdenoCa (80%) ~ Lung or Breast.
  2. Unknown 10%
  3. Lymphoma 15% - both HD and NHL at presentation

Nodules without Effusions

  1. AdenoCa
  2. Lymphoma
  3. Thymoma

Most malignant exudates are non-specific in appearance on CECT.
But some modestly useful features are:

  • Pleural nodules & nodular pleural thickening.
  • Diffuse pleural thickening.
  • Mediastinal pleural involvement.
  • Circumferential Distribution or Parietal thickening >1cm.

But, AdenoCa & malignant mesothelioma are often indistinguishable.

ON MRI. High T2 or increased Gd in relation to intercostal muscle are signs of malignancy.

Treatment Response

Identical lung mets grow at different rates and respond variably to chemo. Thus measure several.
Cavitation and Ca2+ = Sign of response esp in urothelial and CRC.

Radiofrequency Ablation

Causes inflammation, haemorrhage and necrosis of tumour into surrounds.

Phases

  1. Initial -> Increase in size and affected areas on ground glass.
  2. Then, changes to consolidation within a month and reaches maximum size at 1/12.
  3. <=3/12 -> get cavitation and pleural thickening and LN.
  4. 3 - 6/12 -> decrease in size as resorption and fibrosis.

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