Tumors of the lung can either be benign (non-cancerous) or malignant (cancerous). There are certain tumors that are classified as atypical (uncertain or unspecified behavior) meaning that some behave in a benign manner, or some behave in a malignant manner. A majority of the pulmonary tumors diagnosed via lab studies (biopsy) are benign.

The World Health Organization (WHO) is an authoritative body that compiles, prepares, and publishes histological and molecular classification of tumors, via their Blue Books, based on research inputs from experts worldwide. These reference books chiefly aid in global cancer research, provide gold standards for tumor diagnosis, and help in treating cancer patients.

According to the WHO Classification of Thoracic Tumors (2021), 5th Ed., Vol.5, benign and malignant tumors of the lung are classified in the following manner:

Tumors of the lung:

Epithelial tumors

• Papillomas
  • Bronchial papillomas
• Adenomas
  • Sclerosing pneumocytoma
  • Alveolar adenoma: It is a benign tumor of the lung that mostly develops in the lung tissue and not in the airways. These tumors are generally observed in middle-aged and older adults
  • Papillary adenoma of the lung: It is an uncommon benign tumor of the lung that mostly develops in the lung tissue and not in the airways. It is usually observed in children and adults
  • Bronchiolar adenoma / ciliated muconodular papillary tumor
  • Mucinous cystadenoma of the lung: It is a rare benign tumor of the lung, which mostly occurs in the lung tissue. These tumors are generally observed in older adults
  • Mucous gland adenoma of the lung: It is a rare benign tumor of the lung, which occurs predominantly in the lung tissue. It is usually observed in children and adults
• Precursor glandular lesions
  • Atypical adenomatous hyperplasia of the lung: It is a small-sized preinvasive lesion that is characterized by an abnormal growth of cells in the alveolar walls or bronchioles. A majority of these lesions are diagnosed in middle-aged and older adults
  • Adenocarcinoma in situ of the lung: It is a small-sized, localized, premalignant adenocarcinoma. The majority of cases are diagnosed in older adults
• Adenocarcinomas
  • Minimally invasive adenocarcinoma of the lung: It is a small-sized malignant tumor that is diagnosed in older adults
  • Invasive non-mucinous adenocarcinoma of the lung
  • Invasive mucinous adenocarcinoma of the lung: It forms a new category of lung malignancy that is diagnosed in older adults
  • Colloid adenocarcinoma of the lung: It is a histological variant of pulmonary adenocarcinoma. The tumor is generally detected and diagnosed in adults over 65 years’ old
  • Fetal adenocarcinoma of the lung: It is a histological variant of pulmonary adenocarcinoma. The tumor is generally diagnosed in adults
  • Enteric-type adenocarcinoma of the lung: It is a histological variant of pulmonary adenocarcinoma. The tumor is generally detected and diagnosed in adults over 65 years’ old
• Squamous precursor lesions
  • Squamous dysplasia and carcinoma in situ of the lung
• Squamous cell carcinomas
  • Squamous cell carcinoma of the lung: It is a type of lung cancer that mostly affects tobacco smokers; there is a very strong association between this cancer type and smoking. The carcinoma is generally noted in adult men and women
  • Lymphoepithelial carcinoma of the lung
• Large cell carcinomas
  • Large cell carcinoma of the lung: It is a type of lung cancer that is described as an undifferentiated non-small cell carcinoma without having the histological features of adenocarcinoma, small cell carcinoma, and squamous cell carcinoma. The carcinoma is generally noted in adult men and women
• Adenosquamous carcinoma
  • Adenosquamous carcinoma of the lung: It is a rare, malignant tumor of the lungs having malignant squamous cells and malignant glandular cells. The carcinoma is generally noted in adult men and women
• Sarcomatoid carcinomas
  • Pleomorphic carcinoma of the lung: It is a rare type of non-small cell lung carcinoma that is poorly-differentiated. The tumor is generally diagnosed in adults
  • Pulmonary blastoma: It is a rare and aggressive form of lung cancer that contains the presence of two main components - fetal adenocarcinoma and primitive mesenchymal stroma. Middle-aged adults are mostly affected by this tumor type
  • Carcinosarcoma of the lung: It is a very rare type of sarcomatoid carcinoma that can develop anywhere in the peripheral region of the lungs. The tumor is generally diagnosed in adults
• Other epithelial tumors
  • NUT carcinoma of the lung (see NUT carcinoma of the thorax): It is an extremely uncommon and aggressive malignancy that is named due to the presence of an abnormality involving the NUT gene. A wide age range of individuals may be affected
  • Thoracic SMARCA4-deficient undifferentiated tumor
• Salivary gland-type tumors
  • Pleomorphic adenoma of the lung: It is a benign tumor of the lung, which can occur either in the lung tissue or within the bronchial airways. These tumors are observed in both children and adults
  • Adenoid cystic carcinoma of the lung: It is a rare and unusual form of malignancy that is typically observed in middle-aged and older adults. The tumor may be present in the lung tissue or within the bronchial airways
  • Epithelial-myoepithelial carcinoma of the lung: It is an infrequent type of lung cancer that affects both men and women. It is described as a low-grade tumor
  • Mucoepidermoid carcinoma of the lung: It is an uncommon type of lung cancer of the epithelial cells. It has been diagnosed in a wide age range of individuals
  • Hyalinizing clear cell carcinoma of the lung
  • Myoepithelioma and myoepithelial carcinoma of the lung: Myoepithelioma of Lung is a benign tumor of the lung, which can occur either in the lung tissue or within the bronchial airways. Myoepithelial carcinoma of lung is a malignancy that can occur either in the lung tissue or within the bronchial airways. Most of these tumors are observed in adults

Lung neuroendocrine neoplasms

• Lung neuroendocrine neoplasms
• Precursor lesion
  • Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia
• Neuroendocrine tumors
  • Carcinoid/neuroendocrine tumor of the lung: These are uncommon neuroendocrine tumors that constitute of the following two main types - typical carcinoid and atypical carcinoid tumors. The tumors are usually diagnosed in adults under 60 years’ of age
• Neuroendocrine carcinomas
  • Small cell lung carcinoma: It is a high-grade lung cancer that exhibits neuroendocrine features. Almost all individuals affected are heavy to very heavy smokers
  • Large cell neuroendocrine carcinoma of the lung: It is a high-grade lung cancer that exhibits neuroendocrine features. A great majority of the individuals affected are heavy smokers

Tumors of ectopic tissues

• Melanoma of the lung: Primary Melanoma of Lung is an extremely uncommon tumor affecting the lung airways. It is typically observed in older men and women
• Meningioma of the lung

Mesenchymal tumors specific to the lung

• Pulmonary hamartoma: It is a benign lung tumor that can occur either in the lung tissue or within the bronchial airways. These tumors are observed in middle-aged and older adults
• Pulmonary chondroma: It is a rare and benign lung tumor composed of cartilage that mostly affect the lung tissue, or sometimes the bronchus. It is usually observed in adults
• Diffuse pulmonary lymphangiomatosis: It is a rare and aggressive condition of the lungs observed at birth or during childhood
• Pleuropulmonary blastoma: It is an aggressive and rare form of lung cancer that is found in children. It is believed to be related to other childhood tumors such as Wilms tumor, hepatoblastoma, retinoblastoma, and neuroblastoma
• Pulmonary artery intimal sarcoma: It is an extremely rare tumor that may be an undifferentiated tumor or show components of other sarcomas. It may be present in individuals of all age groups
• Congenital peribronchial myofibroblastic tumor: It is a very uncommon tumor affecting the lung airways. The tumor is typically present at birth
• Primary pulmonary myxoid sarcoma with EWSR1-CREB1 fusion: It is an extremely uncommon tumor affecting the lung airways that is usually seen in young women
• PEComatous tumors
  • Lymphangioleiomyomatosis of the lung
  • PEComa of the lung

Hematolymphoid tumors

• Hematolymphoid tumors of the lung
• MALT lymphoma of the lung: It is a non-gastric type of extranodal marginal zone lymphoma of lung. The condition mostly affects older adults. It is also known as marginal zone lymphoma of lung
• Pulmonary diffuse large B-cell lymphoma: It is a rare, B-cell non-Hodgkin’s lymphoma that affects elderly men and women. It is the most common subtype of lymphoma of lung
• Lymphomatoid granulomatosis of the lung
• Intravascular large B-cell lymphoma of the lung: It is a very uncommon, B-cell non-Hodgkin’s lymphoma, generally affecting adults. The condition is usually systemic and can affect the central nervous system
• Pulmonary Langerhans cell histiocytosis
• Pulmonary Erdheim-Chester disease

Additional lung tumor articles (on DoveMed) that are not part of WHO Classification of Thoracic Tumors:

Angiomyolipoma of Lung: It is an extremely uncommon extrarenal angiomyolipoma that may be present in the lung in adult men and women. An angiomyolipoma is a benign tumor that is a mixture of blood vessels, smooth muscles, and fat.

Atypical Adenomatous Hyperplasia of Lung: It is a small-sized preinvasive lesion that is characterized by an abnormal growth of cells in the alveolar walls or bronchioles. Most of these cases are diagnosed in adults.

Atypical Carcinoid Tumors of Lung: It is a less common type of carcinoid lung tumor. It is an intermediate-grade malignancy that is usually diagnosed in adults under 60 years’ of age.

Basaloid Squamous Cell Carcinoma of Lung: It is a rare and poorly-differentiated histological variant of pulmonary squamous cell carcinoma. The carcinoma is generally noted in adult men and women.

Benign Metastasizing Leiomyoma of Lung: A benign metastasizing leiomyoma is a rare tumor generally observed in middle-aged and older women. It may be seen at various body locations, but the most common site is the lung.

Combined Large Cell Neuroendocrine Carcinoma of Lung: It is a type of large cell neuroendocrine carcinoma with additional non-small cell carcinoma histological component of any proportion. The malignancy is diagnosed in adults over the age of 65 years.

Combined Small Cell Carcinoma of Lung: It is a type of small cell lung carcinoma with additional non-small cell carcinoma histological component of any proportion. The malignancy is diagnosed in adults over the age of 65 years.

DICER1-Related Pleuropulmonary Blastoma Cancer Predisposition Syndrome: It is a rare congenital disorder that causes a moderately increased risk for certain cancers and tumors. The presentation of symptoms may occur in childhood or adulthood.

Diffuse Idiopathic Pulmonary Neuroendocrine Hyperplasia: It is a preinvasive condition that is caused by the abnormal growth of neuroendocrine cells of the lung. It is often diagnosed in adults.

Endobronchial Lipoma (EL): It is a very rare and benign lung tumor composed of fat tissues that generally occur within the bronchial airways. These lung tumors are solitary and generally observed in older men.

Epithelioid Hemangioendothelioma of Lung: It is a malignant tumor affecting the lung. Studies indicate that the tumor may be low-to-intermediate grade malignancy. The tumor is observed in individuals (mostly females) of any age category.

Giant Cell Carcinoma of Lung: It is a very rare type of cancer that does not contain any differentiated carcinomatous component, but only pure ‘malignant’ giant cells. The majority of cases are diagnosed in adults over the age of 65 years.

Inflammatory Myofibroblastic Tumor of Lung: It is a rare and mostly benign tumor of the lung. The tumor can grow to large sizes and are observed in middle-aged adults.

Invasive Adenocarcinoma of Lung: It is the most commonly diagnosed type of lung cancer. It is a type of non-small cell lung cancer that usually develops in the peripheral region of the lungs. The majority of cases are detected in adults over the age of 65 years.

Keratinizing Squamous Cell Carcinoma of Lung: It is a histological variant of pulmonary squamous cell carcinoma. The carcinoma is generally noted in adult men and women.

Large Cell Carcinoma of Lung: It is a type of lung cancer described as an undifferentiated non-small cell carcinoma without having the histological features of adenocarcinoma, small cell carcinoma, or squamous cell carcinoma. The average age of individuals with the carcinoma is around 60 years.

Lepidic Adenocarcinoma of Lung: It is a histological subtype of pulmonary adenocarcinoma, a most commonly diagnosed type of lung cancer. It mostly affects individuals over the age of 65 years.

Lymphoepithelioma-like Carcinoma (LELC) of Lung: It is a rare and unusual type of lung carcinoma. The majority of cases are diagnosed in slightly younger adults.

Lymphoma of Lung: It is an uncommon lymphoma that is generally observed in older men and women. The condition may be termed primary or secondary.

Micropapillary Adenocarcinoma of Lung: It is a histological subtype of pulmonary adenocarcinoma, a most commonly diagnosed type of lung cancer. It mostly affects individuals over the age of 65 years.

Myelolipoma of Lung: A myelolipoma is a rare tumor that is seen among a wide age range of adults. It can occur at various locations in the body. The lung is an uncommon site for this tumor.

Non-Keratinizing Squamous Cell Carcinoma of Lung: It is a histological variant of pulmonary squamous cell carcinoma. The carcinoma is generally noted in adult men and women.

Non-Small Cell Lung Cancer: It is a difficult to diagnose malignancy. Some of the non-small cell lung cancer types include adenocarcinoma, squamous cell carcinoma, and large cell carcinoma of the lung. A majority of these tumors are detected in older adults.

Papillary Adenocarcinoma of Lung: It is a histological subtype of pulmonary adenocarcinoma, a most commonly diagnosed type of lung cancer. It mostly affects individuals over the age of 65 years.

Pleuropulmonary blastoma: It is an aggressive and rare form of lung cancer that is found in children.

Primary Benign Teratoma of Lung: A teratoma of lung may be cancerous or benign. A majority of benign teratomas are mature teratomas, while a majority of malignant teratomas are immature teratomas. This benign tumor may be seen in children and young adults.

Primary Malignant Teratoma of Lung: A teratoma of lung may be cancerous or benign. A majority of benign teratomas are mature teratomas, while a majority of malignant teratomas are immature teratomas. The malignancy may be seen in children and young adults.

Pulmonary Glandular Papilloma: It is a rare, benign tumor that can occur either in the lung tissue or within the bronchial airways. It is usually observed in older adults.

Pulmonary Leiomyoma: It is a rare, benign tumor that is generally observed to develop in the lung tissue. A leiomyoma is a benign smooth muscle tumor that can develop anywhere in the body. these tumors are typically observed in young women.

Pulmonary Mixed Squamous Cell and Glandular Papilloma: It is a rare benign tumor that can occur either in the lung tissue or within the bronchial airways. These tumors are generally observed in older adults.

Pulmonary Paraganglioma: It is a very rare and benign tumor of lung that generally affects men and women. The tumors are observed to mostly develop in the lung tissues.

Pulmonary Sclerosing Hemangioma: It is a generally solitary tumor that is often observed in women, who are in their 50s. Hemangiomas are typically benign malformations of blood vessels.

Sarcomatoid Carcinoma of the Lung: It is a type of lung cancer that is a subtype of non-small cell lung cancer. The average age of adults at diagnosis is 65 years.

Small-Cell Lung Cancer: It is a fast-growing type of lung cancer that metastasizes faster than non-small cell types. Small-cell lung cancer types include small cell carcinoma and combined small cell lung carcinoma. A majority of these tumors are detected in older adults.

Solid Adenocarcinoma of Lung: It is a histological subtype of pulmonary adenocarcinoma that mostly affects adults over the age of 65 years.

Solitary Fibrous Tumor of Lung: It is a mostly benign overgrowth arising from the mesenchymal tissue. It may be present in individuals between 20 and 70 years of age.

Spindle Cell Carcinoma of Lung: It is a very rare type of carcinoma that does not contain any differentiated carcinomatous component, but only pure ‘malignant’ spindle cells. The malignancy is diagnosed in older adults.

Squamous Cell Papilloma of Lung: It is a very rare and benign tumor. This tumor is often solitary and generally observed in young and middle-aged adults.

Synovial Sarcoma of Lung: It is a rare malignancy of the lung, even though the lung is the most frequently involved ‘organ’ by a synovial sarcoma. The tumor mostly develops in older adults.

Teratoma of Lung: It is the most common type of germ cell tumor of the lung. It is mostly observed in older children and young adults.

Type I Pleuropulmonary Blastoma: It is an aggressive and rare form of lung cancer that is found in children below the age of 2 years. It is purely cystic in nature.

Type II Pleuropulmonary Blastoma: It is an aggressive and rare form of lung cancer that is found in children at around age 3 years. It is both cystic and solid in nature.

Type III Pleuropulmonary Blastoma: It is an aggressive and rare form of lung cancer that is found in children at around age 3.5 years. It is purely solid in nature.

Typical Carcinoid Tumor of Lung: It is a common type of carcinoid lung tumor. It is a low-grade malignancy that is usually diagnosed in adults under 60 years’ of age.