{"paper_id":"f08ba22b-9cc6-4f6f-8581-fc1411492681","body_text":"In this edition of the AJTCCM, we are reintroduced to the concept of\n‘scarcinoma’, referring to a carcinoma that originates from peripheral\nscarring of lung tissue. The first real description of this entity was by\nthe histopathologist Friederich [1]  in 1939, but it is not included as a\ndistinct histological subtype in the latest International Association for\nLung Cancer study. [1 , 2]  Brett  et al .\n [3]  reviewed radiological data from\n~900 patients over a 5-year period with a histologically confirmed\ndiagnosis of lung cancer, and describe the presence of scarring within\nthe lungs present on computed tomography (CT) of the chest. [3] \nTheir findings demonstrate a clear association, with one-third of the\npatients reviewed having scar tissue present within the lungs within\nthe same lobe as the diagnosed cancer.\nThis is an important study in that it examines the largest\ncohort to date describing ‘scarcinoma’ in a study population with\na high prevalence of smoking and one of the highest burdens of\npulmonary tuberculosis (TB) universally. [4]  Most of the debate\naround the entity of scar-carcinoma hinges on the premise that\nthe scar in the region of the lung cancer is the host response to\nthe malignancy (desmoplastic reaction). [5 , 6]  However, there is the\npossibility that the inflammatory milieu within the scar actually\npredisposes the host to the development of a neoplastic process.\nPatients with idiopathic pulmonary fibrosis (IPF) and other\nfibrotic lung diseases have increased rates of lung cancer, with a\nreported prevalence as high as 48% in autopsy series of patients\nwith usual interstitial pneumonia. Anatomically, the distribution\nof lung cancers in patients with IPF is predominantly lower lobe\nand peripheral, the same regions in which fibrosis is accentuated\nin IPF. [7]  That this might be a ‘cause and effect’ phenomenon will\nhave to be investigated further. Nonetheless, Brett  et al .\n [3]  have documented a similar finding, with the presence of scarring not\njust in the vicinity of the cancer, but on the CT scan as a whole.\nThey have been able to show that while malignancy and fibrosis are\nmuch more common within the same lobe, there is an association\nwith the presence of lung scarring documented anywhere in the\nlung, and lung cancer.\nHowever, what this study highlights is that in a population with a\nhigh prevalence of lung scarring due to chronic ongoing inflammation\nfrom undiagnosed as well as untreated infections such as TB, as\ntreating physicians, we have to be vigilant to the presence of an occult\nmalignancy. There is a published body of literature confirming the\nindependent risk factor that pulmonary TB poses for the development\nof lung cancer. [5]  This study adds further support to the recently\npublished lung cancer screening guidelines of the South African\nThoracic Society, advocating the use of low-dose CT chest scans as an\nappropriate tool for identifying lung cancer at a stage when a curative\ntherapeutic option could still be offered to patients. In patients with\nlung scarring identified on plain chest X-ray, the morphological\ncharacteristics of a malignancy can often be hidden by the radiological \n‘noise’ associated with fibrosis and anatomical distortion of the lung\nparenchyma. Therefore, a CT scan of the chest may be of value in\nidentifying malignancies hiding with the scar tissue. [8]\nPatients with significant risk factors suggestive of ‘scarcinoma’,\nnamely previously documented lung scarring or old TB scarring, a\nfamily history suggestive of lung malignancies, a smoking history\nor an occupational history in the presence of unexplained weight\nloss and a chronic cough, with or without haemoptysis, need to be\ninvestigated further. The diagnostic tool of choice is debatable, but\nthe use of biological imaging such as a positron emission tomography\nscan has added to our armamentarium in identifying the presence of\na ‘scarcinoma’. Furthermore, this study opens the pathway to further\ninvestigate the neglected entity of ‘scarcinoma’. With the advent of\nmore specific radiological tools such as magnetic resonance imaging of\nthe lung, and better molecular and immunohistochemical diagnostic\nmarkers, we might be able to resolve the debate about whether\n‘scarcinoma’ actually exists as a separate clinical entity with a different\nbehavioural pattern. [9]","source_license":"CC-BY-4.0","license_restricted":false}