What are the signs and symptoms of pulmonary carcinoid tumors?
Figure 1: Bronchoscopic appearance of Bronchial carcinoid
The behavior of these tumors depends upon their location within the lungs, whether they secrete hormones, or if they have spread or metastasized. Most of these tumors are located closer to the trachea or main windpipe. These tumors can block free flow in the branches or bronchi (Figure 1) that carry the gases we breathe to and from the segments of the lung. This blockage leads to the most common presentation of recurrent pneumonia or pneumonia that does not completely resolve despite antibiotic treatment. It may also cause wheezing on just one side. Even though these tumors may be quite small (less than 2cm or approximately 3/4 of an inch) they may have a very rich blood supply and can bleed spontaneously or when they are biopsied. Sometimes patients will have a cough or cough up blood. Other common symptoms include fever, chest discomfort and chest pain, and shortness of breath. Chest x-rays or CT scans done to evaluate something completely unrelated to the carcinoid frequently result in the discovery of an asymptomatic carcinoid.
Figure 2: Typical carcinoid 40x magnification H&E
Figure 3: Atypical carcinoid 40x magnification H&E
When the tumor is located more peripherally or further out in the lung, it may become much larger (5cm or 2 inches) before it is detected. Such tumors are more likely to be atypical carcinoids and are more likely to have metastasized to lymph nodes by the time they are diagnosed. Thymic carcinoids behave similarly to the more peripherally located atypical lung carcinoids and occur in the familial tumor syndrome MEN1. These tumors arise in the thymus gland, which is directly behind the breastbone above the heart. Carcinoid tumors are also distinguished by how they grow or behave at a cellular level. Typical carcinoids are more benign appearing histologically (when examined under the microscope) (Figure 2) and behave less aggressively (metastasize less often) than atypical carcinoids. (Figure 3) Both grow very slowly and spread to lymph nodes much less often compared to neuroendocrine small cell and large cell lung carcinoma. The atypical tumors are more likely to be seen in patients age 50-60 while typical carcinoids occur in patients 10 years younger.