Pulmonary neuroendocrine tumors are neuroendocrine tumors localized to the

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

bronchus A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronchus. ...

or pulmonary parenchyma. Pulmonary neuroendocrine tumors include a spectrum of tumors from the low-grade

typical pulmonary carcinoid tumor Typical pulmonary carcinoid tumour is a subtype of pulmonary carcinoid tumour. It is an uncommon low-grade malignant lung mass that is most often in the central airways of the lung. Signs and symptoms Lung carcinoids typically present with a coug ...

and intermediate-grade atypical pulmonary carcinoid tumor to the high-grade pulmonary large cell neuroendocrine carcinoma (LCNEC) and

pulmonary small cell carcinoma Small-cell carcinoma is a type of highly malignant cancer that most commonly arises within the lung, although it can occasionally arise in other body sites, such as the cervix, prostate, and gastrointestinal tract. Compared to non-small-cell lung ...

(SCLC), with significant clinical, epidemiologic and genetic differences.

Types

Pulmonary neuroendocrine tumor are classified according to tumoral grade: * Low grade pulmonary neuroendocrine tumor: Typical pulmonary carcinoid tumour (TC; low-grade); * Intermediate-grade pulmonary neuroendocrine tumor:

Atypical pulmonary carcinoid tumour Atypical pulmonary carcinoid tumour is a subtype of pulmonary carcinoid tumor. It is an uncommon low-grade malignant lung mass that is most often in the central airways of the lung. It is also known as "atypical lung carcinoid tumour", " atypica ...

(AC; intermediate-grade) * High-grade pulmonary neuroendocrine tumor **

Small cell lung cancer Small-cell carcinoma is a type of highly malignant cancer that most commonly arises within the lung, although it can occasionally arise in other body sites, such as the cervix, prostate, and gastrointestinal tract. Compared to non-small cell ca ...

(SCLC) **

Large cell neuroendocrine carcinoma Large cell neuroendocrine carcinoma of the lung (LCNEC) is a highly malignant neoplasm arising from transformed epithelial cells originating in tissues within the pulmonary tree. It is currently considered to be a subtype of large cell lung carci ...

(LCNEC of the lung) Low-grade nodular neuroendocrine proliferations ≥ 0.5 cm are classified as

carcinoid tumor A carcinoid (also carcinoid tumor) is a slow-growing type of neuroendocrine tumor originating in the cells of the neuroendocrine system. In some cases, metastasis may occur. Carcinoid tumors of the midgut (jejunum, ileum, appendix, and cecum) a ...

s and smaller ones are called pulmonary tumorlets. When neuroendocrine cell hyperplasia and tumorlets are extensive, they represent the rare preinvasive lesion for carcinoids known as " diffuse idiopathic pulmonary neuroendocrine cell hyperplasia". Both LCNEC and SCLC can demonstrate histologic heterogeneity with other major histologic types of lung carcinoma, such as pulmonary adenocarcinoma or pulmonary squamous cell carcinoma, but is not characteristic of TC or AC.

Risk factor

Multiple endocrine neoplasia type I Multiple endocrine neoplasia type 1 (MEN-1) is one of a group of disorders, the multiple endocrine neoplasias, that affect the endocrine system through development of neoplastic lesions in pituitary, parathyroid gland and pancreas. It was first d ...

(

MEN1 Menin is a protein that in humans is encoded by the ''MEN1'' gene. Menin is a putative tumor suppressor associated with multiple endocrine neoplasia type 1 (MEN-1 syndrome). ''In vitro'' studies have shown that menin is localized to the nucleus, ...

)can be found in

patients, but not those with LCNEC and SCLC.

Genetics

Genetic changes are very high in SCLC and LCNEC, but usually low for TC, intermediate for AC.

Diagnosis

The diagnosis of SCLC, TC and AC can be made by light microscopy without the need for special tests in most cases, but for LCNEC it is required to demonstrate NE differentiation by immunohistochemistry or electron microscopy.

References

{{reflist Pulmonary tumour