Atypical adenomatous hyperplasia of the lung
Updates to Article Attributes
Atypical adenomatous hyperplasia (AAH) of the lung is a putative precursor lesion of adenocarcinoma of the lung. This entity replaces part of a spectrum of the former bronchoalveolar carcinoma (BAC).
Pathology
AAHs are represented by localised small cell proliferation, usually measuring ≤0.5 cm, of mildly to moderately atypical type II pneumocytes and/or Clara cells that line along the alveolar walls, alveolar septae, or respiratory bronchiole 3,5,8. Subgrading of those lesions according to the spectrum of cellularity and atypia is not recommended 8.
Radiographic features
Their radiographic appearances can be somewhat variable but have been commonly described as ground-glass nodules measuring less than 5 mm 3-5, opposed to adenocarcinomas in situ, which are also pre-invasive lesions, that tend to be larger.
-<p><strong>Atypical adenomatous hyperplasia (AAH) of the lung</strong> is a putative precursor lesion of <a href="/articles/adenocarcinoma-of-the-lung">adenocarcinoma of the lung</a>. This entity replaces part of a spectrum of the former <a href="/articles/adenocarcinoma-in-situ-minimally-invasive-adenocarcinoma-and-invasive-adenocarcinoma-of-lung">bronchoalveolar carcinoma (BAC)</a>.</p><h4>Pathology</h4><p>AAHs are localised small cell proliferation, usually measuring ≤0.5 cm, of mildly to moderately atypical type II pneumocytes and/or Clara cells that line along the alveolar walls, alveolar septae, or respiratory bronchiole <sup>3,5,8</sup>. Subgrading of those lesions according to the spectrum of cellularity and atypia is not recommended <sup>8</sup>. </p><h4>Radiographic features </h4><p>Their radiographic appearances can be somewhat variable but have been commonly described as <a href="/articles/ground-glass-density-nodule-1">ground-glass nodules</a> measuring less than 5 mm <sup>3-5</sup>, opposed to <a href="/articles/adenocarcinoma-in-situ-of-the-lung">adenocarcinomas in situ</a>, which are also pre-invasive lesions, that tend to be larger. </p>- +<p><strong>Atypical adenomatous hyperplasia (AAH) of the lung</strong> is a putative precursor lesion of <a href="/articles/adenocarcinoma-of-the-lung">adenocarcinoma of the lung</a>. This entity replaces part of a spectrum of the former <a href="/articles/adenocarcinoma-in-situ-minimally-invasive-adenocarcinoma-and-invasive-adenocarcinoma-of-lung">bronchoalveolar carcinoma (BAC)</a>.</p><h4>Pathology</h4><p>AAHs are represented by localised small cell proliferation, usually measuring ≤0.5 cm, of mildly to moderately atypical type II pneumocytes and/or Clara cells that line along the alveolar walls, alveolar septae, or respiratory bronchiole <sup>3,5,8</sup>. Subgrading of those lesions according to the spectrum of cellularity and atypia is not recommended <sup>8</sup>. </p><h4>Radiographic features </h4><p>Their radiographic appearances can be somewhat variable but have been commonly described as <a href="/articles/ground-glass-density-nodule-1">ground-glass nodules</a> measuring less than 5 mm <sup>3-5</sup>, opposed to <a href="/articles/adenocarcinoma-in-situ-of-the-lung">adenocarcinomas in situ</a>, which are also pre-invasive lesions, that tend to be larger. </p>
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