Normal

• alveoli
• interstitium
  • airways
  • vessels
• developmental stages
  • embryonic: 3-7 weeks, tubules, pseudostratified lining
  • pseudoglandular: 7-16 weeks, denser tubules (early), simple cuboidal lining with subnuclear vacuoles (late)
  • canalicular: 2nd trimester, branched tubules, cuboidal lining
  • saccular: 3rd trimester, flat lining, losing interstitial mesenchyme
  • alveolar: mid 3rd trimester, back-to-back alveoli (loss of mesenchyme)

medical

neoplasm

Grading

• Grade1: lepidic pattern or well differentiated
• Grade2: acinar, papillary patterns, or moderately differentiated
• Grade3: micropapillary, solid, mucinous, or poorly differentiated
• Grade4: small cell carcinoma, large cell carcinoma, or undifferentiated

TNM (useful for grossing)

• T1: <= 3cm or superficial spreading
• T2
  • > 3cm
  • involves main bronchus, >= 2cm distal to carina
  • invades visceral pleura (disrupts elastic layer, do elastin stain)
  • partial atelectasis or obstructive pneumonitis
• T3
  • involves...
    • chest wall
    • diaphragm
    • mediastinal pleura
    • parietal pericardium
    • main bronchus, < 2cm distal to carina
  • entire lung atelectasis or obstructive pneumonitis
• T4
  • involves...
    • mediastinum
    • heart
    • great vessels
    • trachea
    • esophagus
    • vertebral body
    • carina
  • separate nodules in the same lobe
  • malignant pleural effusion
• superficial spreading: invasion limited to bronchial wall
• Regional nodes: intrathoracic, scalene, supraclavicular
• N1: ipsilateral peribronchial, hilar, or intrapulmonary
• N2: ipsilateral mediastinal or subcarinal
• N3
  • contralateral mediastinal or hilar
  • scalene or supraclavicular
• M1: distant metastasis, including separate nodule in different lobe

Staging

• 0: Tis
• IA: T1
• IB: T2
• IIA: T1N1
• IIB: T2N1 or T3
• IIIA: T3N1 or N2
• IIIB: T4 or N3
• IV: M1