Diagnosis of Small cell lung cancer

Small cell lung cancer diagnosis depends on identifying the specific symptoms, analyzing the patients’ detailed history and also conducting specialized tests. It is a type of aggressive cancer that spreads rapidly. Small cell lung cancer is histologically the malignant epithelial tumor. It consists of small cells with scant cytoplasm and absent or inconspicuous nucleoli ^​1​. The typical type of small cell lung cancer involves small cells and comprises approximately 90% of the total cases. The rest of the issues categorizes into a combined disease where the tumor consists of significant cell components. Some of the diagnostic tests for small cell lung cancer are:

Imaging diagnosis

The samples of biopsy determine the imaging test. The chest x-rays and scan results in addition to the individual’s medical history and other physical examinations, blood tests, and information from the biopsy are in use to get complete details regarding the beginning of the cancer development and its level of spread within the body. Some of the imaging tests are :

CT scan

In this scanning technique, x-rays produce three-dimensional, cross-sectional images of the lungs and surrounding tissues on a computer monitor. This technique detects the cell’s suspicious growth, and the diagnosis of the larger size of the lymph nodes. It also focuses on trapping of the foreign invaders such as viruses and bacteria through small immune system glands. Hence, it results in the confirmation of the lymph nodes containing the cancerous cells. The patients get contrast solutions before the scan in liquid or injection into the vein to enhance the images. 

Positron emission tomography (PET) scan

They doctors conduct it if they find the growth of the cell to be suspicious to cancer. The CT portion of this scan utilizes the x-rays for generating detailed, cross-sectional images of the body. The PET scan uses the specialized camera for determining the rapid growth of the cells. The scan does this through injecting a small amount of radioactive glucose into the vein, which collects within cancer tissues. The PET scan also helps the doctors determine the cancerous growth of the cells and its aggressiveness within the lungs. Also, it also checks the metastasis of cancerous cells throughout the body. 

Magnetic resonance imaging (MRI) scan

It utilizes a magnetic field and radio waves to produce cross-sectional images of particular organs and body tissues. The brain’s MRI is to determine the spread of cancer to the brain. 

Bone scan

It utilizes a radioactive tracer to determine the inside features of the bones. The radiation emitted from the tracer is very low to cause any harm to the individuals. Doctors inject this tracer into the suspect’s vein and it then collects in regions of bones detected through the camera. The special camera can see the dye within the bones, which generates the skeleton images for determining whether small cell lung cancer to the other regions of the body. The diagnosis starts by the identification of healthy and unhealthy bones. The healthy bones appear lighter to the camera, while the cancerous region within the bones stands out in the image. 

Clinical diagnosis

Tissue collection protocols and suggesting appropriate treatment is in use for the clinical diagnosis for small cell lung cancer. The doctors need to check the suspicious cells that may develop into lung cancer, for which they need to study the tissue or fluid from and around the lungs. The utilization of different protocols has allowed the doctors to remove cells or use biopsy from the body and determine them under the microscope for cancer determination. Some of the tests are:

Biopsy

As the imaging test can indicate the occurrence of lung cancer, the biopsy gives the confirmation. In a biopsy, the tissue examination under the microscope determines the cell size and shape and whether they show resemblance to small cell lung cancer. Hence, the experts use many techniques for performing biopsies to diagnose small cell lung cancer.

CT-guided biopsy

The doctors are using CT-guided biopsy for removing the tumor tissues when the abnormal cell growth is capable of reaching outside the body quickly rather than from within the passageways of the lungs like other biopsy protocols. The doctors numb the skin with local anesthesia, and later insert a tiny needle between the ribs and into the lung tumor to withdraw a small tissue sample. The CT scans produce images for guiding the hand during the process.

 Bronchoscopy

The surgeon or pulmonologist views or remove the tumor tissue in the airways using a thin, flexible tube with a light towards the end. They insert it into the mouth or nose that goes down through the main windpipe and then into the breathing passages of the lungs. The pulmonologist is an expert in the diagnosis and treatment of lung disease. This test helps visualize the inside features of the lungs and later helps examine the presence of tumors in the lungs. As they detect the tumor, experts use surgical instruments such as small forceps or needles to take tissue or liquid samples through the bronchoscope. Also, fluoroscopy, an imaging technique, is in use for guiding bronchoscopy using two-dimensional X-rays. 

Endobronchial ultrasound (EBUS)

Doctors insert small tools through the mouth or nose and later passed out into the windpipe and chest region. This helps take up the fluid or tissue samples for further examining the specimens. The doctors mostly discuss the lymph nodes, and take the biopsies through ultrasound to guide the bronchoscopy. This is endobronchial ultrasound (EBUS). The patients are also provided with mild doses of anesthesia and sedation.

Needle aspiration/core biopsy

Interventional radiologists are the main people who do it with evolving numbness to the skin as the sample of the lung cancer cells. The doctors initiate this test with smaller sized needles or large-sized needles, whose size varies as per the sample size. The radiologists utilize a chest CT scan or a particular x-ray machine called a fluoroscope to guide needles in removing pieces. Hence, the use of core biopsy helps prove large tissue samples. 

Thoracentesis

They mainly do it by numbing the skin on the chest region and then inserting a needle through the space between the chest wall and the lung consisting of a fluid collection region. This fluid is later in use for cancer cell detection.

Thoracoscopy

It is the testing performed in the operating room while providing local anesthesia to the patient. A small cut is made in the chest wall region, and a unique instrument with a video camera is inserted to examine the inside part of the chest. The recovery time among the patients tends to be shorter while using thoracoscopy due to the smaller incisions being used in the testing. Hence, this type of testing is further referred to as video-assisted thoracoscopic surgery or VATS. Robotic-assisted surgery is another type of invasive surgery which has replaced thoracoscopy.

Mediastinoscopy

It is another type of diagnostic test in an operating room which involves a surgical procedure where the patient is under sedation. The expertise is generally responsible for taking up the lymph node samples from beneath the center of the chest region towards the breastbone by making a small insertion at the top of the breastbone. 

Thoracotomy

This diagnostic test takes place in an operating room which involves a surgical procedure where the patient is under sedation. The patient’s chest has an incision to examine the lung directly and later take tissue samples for testing. It majorly contributed to removing lung tumors.

Sputum cytology

The doctors collect the mucus sample from the patient’s cough, known as sputum or phlegm and later examine it under a microscope for diagnosis. It will further help check the presence of tumor cells within the lungs.

Electromagnetic Navigation Bronchoscopy

It resembles the global positioning system (GPS) in cars, which helps detect lung tumors among patients. The protocol involves the involvement of sensors being used on the chest and back, producing an electromagnetic field. A probe or catheter threading with another sensor on its end is done into the lungs through a bronchoscope. The doctors are using an electromagnetic field for tracking the probe position and bronchoscope on a detailed, three-dimensional CT scan image of the chest as they move through the lungs.

The guidance system is used for performing the biopsies within distant regions of the lungs, which cannot be reached using conventional bronchoscopy. The doctors use this technique for marking small lung tumors with blue color dye for quickly locating during the surgery. The electromagnetic navigation bronchoscopy has been used for placing small fiducial markers and tiny wires, which is detected with imaging scans. These markers are responsible for guiding the targeted radiation therapy or stereotactic body radiation therapy, in which energy beams are used to destroy the cancer cells. 

Pathological diagnosis

The pathological diagnosis is integrated as per the classification of the World health organization (WHO) using the morphology of the small cell lung cancer, including the small cells ranging in shape from uniform to spindle-shaped, sparse cytoplasm, high mitotic index, necrotic areas. Immunohistochemistry is used to identify the markers involving synaptophysin, chromogranin A, CD56, thyroid transcription factor 1, and MIB-1 that helps in the appropriate confirmation of the diagnosis. Depending upon the tumor’s location within the chest regions, the biopsies are usually done by bronchoscopy, mediastinoscopy, endobronchial ultrasound (EBUS), transthoracic needle aspiration, and thoracoscopy. The preferred approach is the biopsy from a metastatic lesion involving the liver, lymph nodes, and subcutaneous nodules during the extensive-stage disease. It will stage the patients pathologically simultaneously ^​2​.  

Clinical research diagnosis

The research on the biomarkers substances in the blood or tissue is in use for the diagnosis of small cell lung cancer ^​3​. The biomarkers have shown efficacy in determining the aggressive condition of tumor cells and integrating appropriate treatment for the same.

References