Table 1

The 1999 World Health Organization/International Association for the Study of Lung Cancer Histological Classification of Lung and Pleural Tumours

1 Epithelial Tumours
 1.1. Benign
  1.1.1. Papillomas
   1.1.1.1. Squamous cell papilloma
    Exophytic
    Inverted
   1.1.1.2. Glandular papilloma
   1.1.1.3. Mixed squamous cell and glandular papilloma
  1.1.2. Adénomas
   1.1.2.1. Alveolar adenoma
   1.1.2.2. Papillary adenoma
   1.1.2.3. Adenomas of salivary-gland type
    Mucous gland adenoma
    Pleomorphic adenoma
    Others
   1.1.2.4. Mucinous cystadenoma
   1.1.2.5. Others
 1.2. Preinvasive lesions
  1.2.1. Squamous dysplasia/Carcinoma in situ
  1.2.2. Atypical adenomatous hyperplasia
  1.2.3. Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia
 1.3. Malignant
  1.3.1. Squamous cell carcinoma
   Variants
   1.3.1.1. Papillary
   1.3.1.2. Clear cell
   1.3.1.3. Small cell
   1.3.1.4. Basaloid
  1.3.2. Small cell carcinoma
   Variant
   1.3.2.1. Combined small cell carcinoma
  1.3.3. Adénocarcinoma
   1.3.3.1. Acinar
   1.3.3.2. Papillary
   1.3.3.3. Bronchioloalveolar carcinoma
    1.3.3.3.1. Non-mucinous (Clara/pneumocyte type II)
    1.3.3.3.2. Mucinous
    1.3.3.3.3. Mixed mucinous and non-mucinous
     or intermediate cell type
   1.3.3.4. Solid adenocarcinoma with mucin
   1.3.3.5. Adenocarcinoma with mixed subtypes
   1.3.3.6. Variants
    1.3.3.6.1. Well-differentiated fetal adenocarcinoma
    1.3.3.6.2. Mucinous (“colloid”) adenocarcinoma
    1.3.3.6.3. Mucinous cystadenocarcinoma
    1.3.3.6.4. Signet-ring adenocarcinoma
    1.3.3.6.5. Clear cell adernocarcinoma
  1.3.4. Large cell carcinoma
   Variants
   1.3.4.1. Large cell neuroendocrine carcinoma
    1.3.4.1.1. Combined large cell neuroendocrine carcinoma
   1.3.4.2. Basaloid carcinoma
   1.3.4.3. Lymphoepithelioma-like carcinoma
   1.3.4.4. Clear cell carcinoma
   1.3.4.5. Large cell carcinoma with rhabdoid phenotype
  1.3.5. Adenosquamous carcinoma
  1.3.6. Carcinomas with pleomorphic, sarcomatoid or sarcomatous elements
   1.3.6.1. Carcinomas with spindle and/or giant cells
    1.3.6.1.1. Pleomorphic carcinoma
    1.3.6.1.2. Spindle cell carcinoma
    1.3.6.1.3. Giant cell carcinoma
   1.3.6.2. Carcinosarcoma
   1.3.6.3. Pulmonary blastoma
   1.3.6.4. Others
  1.3.7. Carcinoid tumour
   1.3.7.1. Typical carcinoid
   1.3.7.2. Atypical carcinoid
  1.3.8. Carcinomas of salivary-gland type
   1.3.8.1. Mucoepidermoid carcinoma
   1.3.8.2. Adenoid cystic carcinoma
   1.3.8.3. Others
  1.3.9. Unclassified carcinoma
2 Soft Tissue Tumours
 2.1 Localized fibrous tumour
 2.2 Epithelioid hemangioendothelioma
 2.3 Pleuropulmonary blastoma
 2.4 Chondroma
 2.5 Calcifying fibrous pseudotumour of the pleura
 2.6 Congenital peribronchial myofibroblastic tumour
 2.7 Diffuse pulmonary lymphangiomatosis
 2.8 Desmoplastic small round cell tumour
 2.9 Other
3 Mesothelial Tumours
 3.1 Benign
  3.1.1 Adenomatoid tumour
 3.2 Malignant
  3.2.1 Epithelioid mesothelioma
  3.2.2 Sarcomatoid mesothelioma
   3.2.2.1 Desmoplastic mesothelioma
  3.2.3 Biphasic mesothelioma
  3.2.4 Other
4 Miscellaneous Tumours
 4.1 Hamartoma
 4.2 Sclerosing hemangioma
 4.3 Clear cell tumour
 4.4 Germ cell neoplasms
  4.4.1 Teratoma, mature or immature
  4.4.2 Malignant germ cell tumour
 4.5 Thymona
 4.6 Melanoma
 4.7 Others
5 Lymphoproliferative Disease
 5.1 Lymphoid interstitial pneumonia
 5.2 Nodular lymphoid hyperplasia
 5.3 Low-grade marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue
 5.4 Lymphomatoid granulomatosis
6 Secondary Tumours
7 Unclassified Tumours
8 Tumour-like Lesions
 8.1 Tumourlet
 8.2 Multiple meningothelioid nodules
 8.3 Langerhans cell histiocytosis
 8.4 Inflammatory pseudotumour (Inflammatory myofibroblastic tumour)
 8.5 Organizing pneumonia
 8.6 Amyloid tumour
 8.7 Hyalinizing granuloma
 8.8 Lymphangioleiomyomatosis
 8.9 Multifocal micronodular pneumocyte hyperplasia
 8.10 Endometriosis
 8.11 Bronchial inflammatory polyp
 8.12 Others