Pulmonary carcinoid tumors are uncommon neuroendocrine epithelial malignancies accounting for less than 1% of all lung cancers. They divide into two subcategories: typical carcinoids and atypical carcinoids. Typical carcinoids and atypical carcinoids are, respectively, low- and intermediate-grade neuroendocrine tumors. Approximately 80% of pulmonary carcinoids occur centrally, and 20% are peripheral

Continuing Education Activity

Pulmonary carcinoid tumors are uncommon neuroendocrine epithelial malignancies accounting for less than 1% of all lung cancers. They divide into two subcategories: typical carcinoids and atypical carcinoids. Typical carcinoids and atypical carcinoids are, respectively, low- and intermediate-grade neuroendocrine tumors. Approximately 80% of pulmonary carcinoids occur centrally, and 20% are peripheral. All bronchial carcinoids are malignant and have the potential to metastasize. This activity reviews the cause and pathophysiology of lung carcinoids and highlights the role of the interprofessional team in its management.

Objectives:

  • Describe the histopathology of lung carcinoids.
  • Review the presentation of lung carcinoid.
  • Summarize the treatment options for lung carcinoid.
  • Outline the importance of improving care coordination among interprofessional team members to improve outcomes for patients affected by lung carcinoid.

Access free multiple choice questions on this topic.Go to:

NPF Broncial Carcinoid Tumours V5 Introduction

Pulmonary carcinoid tumors are uncommon neuroendocrine epithelial malignancies accounting for less than 1% of all lung cancers. They divide into two subcategories: typical carcinoids and atypical carcinoids. Typical carcinoids and atypical carcinoids are, respectively, low- and intermediate-grade neuroendocrine tumors. Approximately 80% of pulmonary carcinoids occur centrally, and 20% are peripheral.[1] All bronchial carcinoids are malignant and have the potential to metastasize.[2]Go to:

NPF Broncial Carcinoid Tumours V5 Etiology

The mechanisms of carcinoid tumor development and progression are not clear, but some cases are postulated to develop in the setting of proliferating pulmonary neuroendocrine cells via diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) and tumorlets.[3]

Some studies also showed a relationship of this tumor to smoking but the causation relationship is still not concrete. Air pollutants and certain chemicals have also shown a few risk factors among other studies. Some data shows a high incidence among whites and women as compared to men.[4]Go to:

NPF Broncial Carcinoid Tumours V5 Epidemiology

Carcinoid tumors comprise less than 1% of primary lung cancers.[5] The mean age at presentation is about 50 years, but they can occur at any age from 5 to 90 years. Atypical carcinoids present approximately one decade later than typical carcinoids. About 8% develop in the second decade, making them the most common primary pulmonary tumor of childhood. Typical carcinoids are not correlated to tobacco smoking, although reports of atypical carcinoids are more frequent in smokers.[6] Risk factors of carcinoids include having a family history of carcinoid tumors and carrying multiple endocrine neoplasia type 1 (MEN1) genes.[7] This shows an inherited pattern of the tumor too.Go to:

NPF Broncial Carcinoid Tumours V5 Pathophysiology

Lung carcinoids are a part of the neuroendocrine tumors (NETs) that arise in the lungs. These NETs could show either a typical low-grade, well-differentiated, slow-growing tumor or they may present as atypical high-grade, poorly differentiated carcinomas. However, the NETs share the capacity to synthesize neuropeptides and the presence of submicroscopic cytoplasmic dense-core.[8]Go to:

NPF Broncial Carcinoid Tumours V5 Histopathology

Macroscopic Findings

Central carcinoid tumors are well-circumscribed, round to ovoid, and sessile or pedunculated. There is salt and pepper chromatin and moderate to abundant eosinophilic cytoplasm. They often fill the bronchial lumen.[9] The tumors may grow between the cartilaginous plates into adjacent tissues. Carcinoids range in size from 0.5 to 9.5 cm. Atypical carcinoids are on average larger than typical carcinoids.[9] 

Histopathology

The growth patterns of carcinoid tumors suggest neuroendocrine differentiation. Organoid and trabecular patterns are most common; however, rosette formation, papillary growth, pseudo-glandular growth, and follicular growth may also be present. The tumor cells are usually uniform in appearance, with finely granular nuclear chromatin, inconspicuous nucleoli, and moderate to abundant eosinophilic cytoplasm.[10] The stroma is classically highly vascularized, but extensive hyalinization, cartilage, or bone formation may be encountered.  There are reports of stromal amyloid as well as the prominent mucinous stroma. Typical carcinoids are carcinoid tumors with less than 2 mitoses per 2mm2 and lacking necrosis. Atypical carcinoid generally shows the same range of histological features as typical carcinoid. The defining features are 2 to 10 mitoses per 2mm2 and/or necrosis.[11] Necrosis is usually punctate. Mitoses counting should be in the area of highest mitotic activity in the fields filled with many viable tumor cells as possible and should also be per 2mm2 rather than ten high-power fields.[10]

Immunohistochemistry

Immunohistochemistry may be a necessity for diagnosis, particularly on small biopsies. An antibody panel including chromogranin A, synaptophysin (both with cytoplasmic labeling), and CD56 (mostly decorating cell membranes) is the recommendation. However, none of these markers distinguish typical carcinoids from atypical carcinoids. Most carcinoids are also reactive for pan-cytokeratin antibodies. Some peripheral tumors also stain with TTF1, which is less specific. The Ki67 labeling index is valuable in biopsy or cytology samples, particularly with crush artifacts where the mitotic index is difficult to assess, to avoid misdiagnosing carcinoid tumors as high neuroendocrine carcinomas.[10]Go to:

NPF Broncial Carcinoid Tumours V5 History and Physical

Almost 25 percent of the people with lung carcinoid tumors may not present with any symptoms of the disease. They may be diagnosed incidentally while being tested for another condition.

The most common presenting symptoms of bronchopulmonary carcinoid tumors are:

  • Coughing or wheezing
  • Hemoptysis
  • Symptoms referable to the consequences of collapse or pneumonia distal to airway obstruction.[1] Sometimes the patients present with stridor.

Since this tumor is primarily a carcinoid tumor, the patient’s may present with symptoms of carcinoid syndrome:

  • Facial flushing
  • Shortness of breath
  • High blood pressure
  • Weight gain
  • Hirsutism
  • Asthma-like symptoms

Small carcinoids may be asymptomatic and only discovered, incidentally.

Most cases are endocrinologically silent at the clinical level. Clinical syndromes secondary to peptide production are uncommon, they include carcinoid syndrome, Cushing syndrome, and acromegaly.[1]

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