A diagnosis of lung cancer may be suspected on the basis of typical symptoms, particularly in a person with smoking history. Symptoms such as coughing up blood and unintentional weight loss may prompt further investigation, such as medical imaging. Classification CT scan-<unk>  of the left lung The majority of lung cancers can be characterized as either small cell lung cancer (SCLC) or non-small cell lung cancer (NSCLC). Lung<unk>  is one of the three major subtypes of NSCLC, which also include squamous carcinoma and large cell carcinoma. Historically, there has been much debate in the most accurate method of describing<unk>  and several revisions of classification systems have been published. Most recently, the International Multidisciplinary Classification of Lung<unk>  was published in 2011 and represents the consensus of several organizations to more accurately describe this specific type of lung cancer. The current classification system aims to more reliably predict prognosis and determination of therapeutic management. The tumor size, pattern of cell growth, and depth of cell invasion into normal lung tissue are considered in determining classification. The following names represent a step-wise pathologic progression in the natural course of<unk>  development;<unk>  in situ (AIS), Minimally invasive<unk>  (MIA), and Invasive<unk> . Invasive<unk>  includes a heterogenous mixture of subtypes and variants. The 2011 consensus describes five subtypes of invasive<unk> s based on the cell pattern that is most predominant. These subtypes are described below: Histopathology of lepidic predominant<unk> . * lepidic predominant * acinar predominant * papillary predominant * micropapillary predominant * solid predominant with mucin production Cell patterns identifying subtypes are associated with prognosis, ranging from favorable (lepidic) to intermediate (acinar and papillary) to poor (micropapillary and solid). Four discrete variants of invasive<unk> s not assignable to these five subtypes are also included in the current classification: * invasive mucinous<unk>  * colloid<unk>  * fetal<unk>  * primary pulmonary enteric<unk>  Imaging A chest x-ray (radiograph) is often the first imaging test performed when a person presents with cough or chest pain, particularly in the primary care setting. A chest radiograph may detect a lung nodule/mass that is suggestive of cancer, although sensitivity and specificity are limited. CT imaging provides better evaluation of the lungs, with higher sensitivity and specificity for lung cancer compared to chest radiograph (although still significant false positive rate). Computed tomography (CT) that is specifically aimed at evaluating lung cancer includes the chest and the upper abdomen. This allows for evaluation of other relevant anatomic structures such as nearby lymph nodes, adrenal glands, liver, and bones which may show evidence of metastatic spread of disease. Indeed, the US Preventative Services Task Force recommends annual screening with low-dose CT in adults aged 55 to 80 years who have a 30 pack-year smoking history and currently smoke or have quit within the past 15 years, with certain caveats (see Lung cancer screening). Nuclear medicine imaging, such as PET/CT and bone scan, may also be helpful to diagnose and detect metastatic disease elsewhere in the body. PET/CT uses a metabolically active tracer that allows clinicians to identify areas of the body that are hypermetabolic. Increased uptake of the tracer occurs in malignant cells and areas of inflammation or infection. Integrating the imaging reflective of metabolic activity with normal CT imaging allows for higher sensitivity and specificity compared to PET alone. MRI is reserved for patients with advanced disease where intracranial, or brain, involvement is likely. It is also helpful for evaluating the extent of chest wall, diaphragmatic, brachial plexus (such as in the case of superior sulcus tumors), or spine involvement. Histopathology If possible, a biopsy of any suspected lung tumor is performed in order to make a microscopic evaluation of the cells involved and is ultimately required to confirm diagnosis. Biopsy should be attempted in distant lesions first to establish a histologic diagnosis and to simultaneously confirm metastatic staging. The biopsy material is also used to analyze whether the tumor express any specific mutations suitable for tageted therapy (eg. EGFR mutation or ALK mutation). Biopsy can be accomplished via bronchoscopy, transthoracic needle biopsy, and video-assisted thorascopic surgery (VATS). While sputum cytology has been shown to have limited utility, thoracentesis, or aspiration of pleural fluid with an ultrasound-guided needle, should be performed when pleural effusion is present. When malignant cells are identified in the pleural aspirate of patients highly suspect for lung cancer, a definitive diagnosis and staging (stage IV<unk>  is established.<unk>  tends to stain mucin positive as it is derived from the mucus-producing glands of the lungs. Similar to other<unk> , if this tumor is well differentiated (low grade) it will resemble the normal glandular structure. Poorly differentiated<unk>  will not resemble the normal glands (high grade) and will be detected by seeing that they stain positive for mucin (which the glands produce).<unk>  can also be distinguished by staining for TTF-1, a cell marker for<unk> . As discussed previously, the category of<unk>  includes are range of subtypes, and any one tumor tends to be heterogeneous in composition. Several major subtypes are currently recognized by the World Health Organization (WHO) and the International Association for the Study of Lung Cancer (IASLC) / American Thoracic Society (ATS) / European Respiratory Society (ERS): lepidic predominant<unk> , acinar predominant<unk> , papillary predominant<unk> , micropapillary predominant<unk> , solid predominant<unk> , and solid predominant with mucin production. In as many as 80% of these tumors, components of more than one subtype will be recognized. Surgically resected tumors should be classified by comprehensive histological subtyping, describing patterns of involvement in increments of 5%. The predominant histologic subtype is then used to classify the tumor overall. The predominant subtype is prognostic for survival after complete resection. To reveal the<unk> tous lineage of the solid variant, demonstration of intracellular mucin production may be performed. Foci of squamous metaplasia and dysplasia may be present in the epithelium proximal to<unk> s, but these are not the precursor lesions for this tumor. Rather, the precursor of peripheral<unk> s has been termed atypical adenomatous hyperplasia (AAH). Microscopically, AAH is a well-demarcated focus of epithelial proliferation, containing cuboidal to low-columnar cells resembling club cells or type II pneumocytes. These demonstrate various degrees of cytologic atypia, including hyperchromasia, pleomorphism, prominent nucleoli. However, the atypia is not to the extent as seen in frank<unk> s. Lesions of AAH are monoclonal, and they share many of the molecular aberrations (like KRAS mutations) that are associated with<unk> s. Signet ring and clear cell<unk>  are no longer histological subtypes, but rather cytological features that can occur in tumour cells of multiple histological subtypes, most often solid<unk> .
Adenocarcinoma of the lung
Giant-cell carcinoma of the lung
Sarcomatoid carcinoma of the lung
Acinic cell carcinoma of the lung
Squamous-cell carcinoma of the lung
Non-small-cell lung carcinoma
Pulmonary sclerosing pneumocytoma
Epithelial-myoepithelial carcinoma of the lung