(1999 WHO/IASLC Revision)

Preinvasive lesions

1. •Squamous dysplasia/carcinoma in situ
   

2. •Atypical adenomatous hyperplasia
   

3. •Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia
   

Invasive Malignant Non-small Cell

Squamous cell carcinoma

Variants:

1. •Papillary
   

2. •Clear cell
   

3. •Small cell
   

4. •Basaloid
   

Adenocarcinoma

1. •Acinar
   

2. •Papillary
   

3. •Bronchioloalveolar carcinoma
   

4. •Non-mucinous
   

5. •Mucinous
   

6. •Mixed mucinous and non-mucinous or indeterminate
   

7. •Solid adenocarcinoma with mucin formation
   

8. •Mixed
   

Variants:

1. •Well-differentiated fetal adenocarcinoma
   

2. •Mucinous ("colloid"),
   

3. •Mucinous cystadenocarcinoma
   

4. •Signet ring
   

5. •Clear cell
   

Large cell carcinoma

1. •Large cell neuroendocrine carcinoma
   

2. •Combined large cell neuroendocrine carcinoma
   

3. •Basaloid carcinoma
   

4. •Lymphoepithelioma-like carcinoma
   

5. •Clear cell carcinoma
   

6. •Large cell carcinoma with rhabdoid phenotype
   

Adenosquamous carcinoma

Carcinomas with pleomorphic, sarcomatoid or sarcomatous elements

1. •Carcinomas with spindle and/or giant cells
   

2. •Pleomorphic carcinoma
   

3. •Spindle cell carcinoma
   

4. •Giant cell carcinoma
   

5. •Carcinosarcoma
   

6. •Blastoma (Pulmonary blastoma)
   

Invasive Malignant Small Cell

Small cell carcinoma

Variants:

1. •Combined small cell carcinoma