Lung Cancer (Small Cell Lung Carcinoma and Non-Small Cell Lung Carcinoma) for USMLE 2

Lung cancers consists of Small Cell Carcinoma, Sqamous Cell Carcinoma, Adenocarcinoma and Large Cell Carcinoma. We will be reviewing Epidemiology, Pathology Pathophysiology, Clinical Signs and Symptoms, Investigations and Treatment/Management of Lung Cancer.

EPIDEMIOLOGY OF LUNG CANCER
Adenocarcinoma is the most common right now and is the most common. It is the third most common cancer and is the most common cause of cancer death.

RISK FACTORS OF LUNG CANCER
Smoking, Asbestos, Radiation, Arsenic Chromium, Nickel.
Genetics, Scar Formation (Wegeners, Fibrosis, Scleroderma)
Air pollution, HIV.

CLINICAL SIGNS AND SYMPTOMS OF LUNG CANCER
Pulmonary Symptoms, most common is cough, Hemoptysis (which ca lead to asphyxia) Chest Pain (dull achy), Dyspnea (secondary to pneumonia, atelectasis, lymphatic tumor spread, pleural effusion and pneumothorax), hoarsenes (when laryngeal nerve involved), pleural effusion (serous, serosangiounous, bloody) which may be caused by metastasis into pleural fluid. Super Vena Cava Syndrome occurs when central tumor invades SVC which causes red, edematous face, prominent veins throughout the body and this is more common in small cell lung cancer. Pancoast tumor is a lung cancer located in the apex of the lungs. Pancoast tumor may lead to thoracic outlet syndrome (pain weakness in arm and hand). Horner Syndrome causes miosis, anhydrosis and ptosis (MAP) and this is more common in Non Small Cell Lung Cancer.

Paraneoplastic syndromes are due to hypercalcemia (PTHrP) bone mets, calcitriol release, cytokine. SIADH causes increase water absorption leading to dilution hyponatremia, cerebral edema, anorexia, nausea vomiting. Resolves with chemo and treatment. Lambert Eaton Myasthenic Syndrome (LEMS) is a condition with auto-antibodies of the calcium channels in the Neuromuscular Junction. Proximal Muscle weakness and rising and standing. Hematologic derangements such as anemia, leukocytosis, thrombocytosis and hypercoagulability. Hypertrophic osteoarthropathy may lead to digital clubbing, periositis, Arthralgia, Cushings due to release of Ectopic ACTH.

Metastasis symptoms occur when metastasis of lung cancer to liver, adrenal gland, Lung, Spine, Brain. Screen with PET-CT.

INVESTIGATIONS FOR LUNG CANCER
X-Ray may show a coin lesion. First step in management is to look at a previous x-ray and look for a sign of lung cancer on the old x-ray.

Cytology of the sputum, bronchoscopy, and percutaneous.

CT Scan and PET CT

Small Cell Lung Cancer
Oat cells look like small cells with little cytoplasm. All are of neuroendocrine origin (feyrter cells) on bronchus. Small Cell Lung Cancer is found central and has limited stage (Lung and 1 lymph node) Extended stage is spread beyond the lungs. Usually has early metastasis. May release ACTH, SIAD, Lambert eaton myasthenic syndrome.

Adenocarcinoma
Mucin and TTF-1 Positive type of Lung Cancer. Graded from low grade to high grade. Bronchoalverolar carcionma is in situ carcinoma and has better prognosis. Most common in Non-Smokers (BAC)

Squamous Cell Lung Cancer
Irritation of bronchus causing metaplasia, then dysplasia, then carcinoma in situ and finally lung cancer. Also associated with Keratin pearls and cavitation from central necrosis. Goes into hilar nodes and gets late metastasis. Asymptomatic and can be deteetd with sputum cytology.


Large Cell Lung Cancer
Lots of cytoplasm, unknown origin and is a waste basket column. Peripheral and has late metastasis and can use cancer.

TREATMENT OF LUNG CANCER
Small Cell Lung Cancer metastasizes early on and therefore surgery is not an option. Cisplatin, Carboplatin and vincristin is also used. Responds very well to chemotherapy. Prophylactic cranial irradiation (PCI) to prevent brain metastasis. Surgery is possible if the tumor is very small and no metastsis

Non Small Cell Lung Cancer is not responsive to chemotherapy or radiotherapy so surgery is the only option.