Adenocarcinoma of the lung
Updates to Article Attributes
Adenocarcinoma of the lung is onethe most common histologic type oflung cancer. Grouped under the non-small cell carcinomas of the lung and, it is a malignant tumour with glandular differentiation or mucin production. This tumour exhibits various expressing in different patterns and degrees of differentiation.
This article brings a broad view over lung adenocarcinoma, including lepidicfor further details on each subtype, acinarplease refer to the specific articles listed below.
Terminology
In 2011, papillarythe International Association for the Study of Lung Cancer (IASLC), micropapillaryAmerican Thoracic Society (ATS), and European Respiratory Society (ERS) introduced a new classification and terminology for adenocarcinoma of the lung, which is now divided into:
- preinvasive adenocarcinoma lesions
- minimally invasive adenocarcinoma
- invasive adenocarcinoma
-
variants of invasive adenocarcinoma
-
invasive mucinous adenocarcinoma
- formerly mucinous BAC
- colloid
- fetal (low and high grade)
- enteric
-
invasive mucinous adenocarcinoma
Epidemiology
It is now considered the most common histological subtype in terms of prevalence.
Clinical presentation
Early symptoms are fatigue with mild dyspnoea followed by a chronic cough and haemoptysis at a later stage.
ClassificationPathology
Lung adenocarcinoma is primarily categorized on the basis of histopathologic evaluation, although testing for genetic mutations (e.g. EGFR, KRAS) is becoming increasingly important for consideration of therapy 1.
Mucinous adenocarcinoma is recognized as distinct from non-mucinous adenocarinomas, given differences in imaging appearance, genetics, and clinical behaviour.
Next, lung adenocarcinomas are divided into 'preinvasive', 'minimally invasive', and 'invasive' disease on the basis of greatest depth of invasion on resection specimens (this assessment is not possible on limited biopsies) 1:
-
preinvasive adenocarcinoma lesions
-
atypical adenomatous hyperplasia (AAH)
- localised small cell proliferation, usually ≤0.5 cm
- histological pattern: a focal proliferation of mildly to moderately atypical type II pneumocytes and/or Clara cells that line along the alveolar walls, alveolar septae, or respiratory bronchiole
-
adenocarcinoma in situ (AIS)
- localised adenocarcinoma of ≤3 cm
- histological pattern: no growth pattern other than lepidic, with neoplastic cells along the alveolar structures but without stromal, vascular, or pleural invasion, and no features of necrosis
- has a number of subtypes: the most common subtype is non-mucinous and, rarely, mucinous or mixed subtypes
-
atypical adenomatous hyperplasia (AAH)
-
minimally invasive adenocarcinoma
- localised adenocarcinoma of ≤3 cm
- histological pattern: either pure lepidic or predominant lepidic growth pattern, with neoplastic cells along the alveolar structures with ≤5 mm of stromal invasion. These lesions should not show necrosis, lymphatic, vascular, or pleural invasion.
- three histopathological subtypes are recognised:
- invasive adenocarcinoma
:(>5 mm invasion
For invasive adenocarcinoma, further) - further subcategorization is recommended according to the dominant histologic pattern. Both mucinous and non-mucinous adenocarcinomas typically consist of a mixture of histologic patterns (all previously known as "mixed subtype", a now-defunct category), but reporting of the predominant subtype is specifically recommended for non-mucinous lesions 1:
-
lepidic predominant adenocarcinoma of the lung
:- formerly non-mucinous bronchioloalveolar carcinoma (BAC)
pattern, with > 5 mm invasion
- formerly non-mucinous bronchioloalveolar carcinoma (BAC)
- acinar predominant adenocarcinoma of the lung
- papillary predominant adenocarcinoma of the lung
- micropapillary predominant adenocarcinoma of the lung
- solid predominant with mucin
Variants:
-
invasive mucinous adenocarcinoma
(formerly-
formerly mucinous BAC
)
-
formerly mucinous BAC
- colloid
- fetal (low and high grade)
- enteric
Radiographic features
Sometimes it is impossible to radiographically distinguish between other histological lung cancer types.
A lung nodule is a rounded or irregular region of increased attenuation measuring less than 3 cm. The amount of attenuation can further classify the nodules as either ground glass, subsolid or solid 1,2.
Histologically, the ground-glass attenuation corresponds to a lepidic growth pattern and the solid component corresponds to invasive patterns. Hence, the preinvasive category of adenocarcinoma in situ, minimally invasive adenocarcinoma, and the invasive subtype of lepidic-predominant adenocarcinoma are often seen as a ground-glass nodule or a subsolid nodule with a predominant ground-glass component. On the other hand, the remaining invasive subtypes of adenocarcinoma usually manifest as a solid nodule but may also be subsolid and are only occasionally seen as ground glass nodule 1,2.
The invasive mucinous adenocarcinoma subtype (formerly mucinous BAC) can have a variable appearance, including consolidation, air bronchograms, or multifocal subsolid nodules or masses 2.
Nuclear medicine
FDG PET/CT
FDG-PET/CT is nowadays an essential tool for the lung cancer staging, in particular, assessing for the nodal and distant metastatic disease
adenocarcinoma in situ, low-grade adenocarcinomas, and minimally invasive adenocarcinoma are commonly associated with PET false-negative results. Given resolution limitations, FDG PET/CT is recommended when assessing subsolid ground-glass lung lesions that have a solid component measuring more than 8 mm 7
PET/CT definition of the gross tumour volume is commonly smaller than on CT, in ~15% of patients 7, therefore the T component of the TNM staging must be measured on CT or updated by the pathological staging
blooming artifact usually makes PET/CT less reliable to assess chest wall or diaphragmatic invasion 7
Treatment and prognosis
There are society guideline recommendations for the imaging follow-up of both ground glass and solid nodules: Fleischner Society guidelines 3.
-<p><strong>Adenocarcinoma of the lung </strong>is one of the <a href="/articles/non-small-cell-lung-cancer-2">non-small cell carcinomas of the lung</a> and is a malignant tumour with glandular differentiation or mucin production. This tumour exhibits various patterns and degrees of differentiation, including lepidic, acinar, papillary, micropapillary, and solid with mucin formation <sup>1</sup>. </p><h4>Epidemiology</h4><p>It is now considered the most common histological subtype in terms of prevalence.</p><h4>Clinical presentation</h4><p>Early symptoms are fatigue with mild dyspnoea followed by a chronic cough and <a href="/articles/haemoptysis-1">haemoptysis</a> at a later stage.</p><h4>Classification</h4><p>Lung adenocarcinoma is primarily categorized on the basis of histopathologic evaluation, although testing for genetic mutations (e.g. <em>EGFR</em>, <em>KRAS</em>) is becoming increasingly important for consideration of therapy <sup>1</sup>.</p><p><a href="/articles/invasive-mucinous-adenocarcinoma-of-the-lung-1">Mucinous adenocarcinoma</a> is recognized as distinct from non-mucinous adenocarinomas, given differences in imaging appearance, genetics, and clinical behaviour.</p><p>Next, lung adenocarcinomas are divided into 'preinvasive', 'minimally invasive', and 'invasive' disease on the basis of greatest depth of invasion on resection specimens (this assessment is not possible on limited biopsies) <sup>1</sup>:</p><ul>- +<p><strong>Adenocarcinoma of the lung </strong>is the most common histologic type of <a href="/articles/lung-cancer-3">lung cancer</a>. Grouped under the <a href="/articles/non-small-cell-lung-cancer-2">non-small cell carcinomas of the lung</a>, it is a malignant tumour with glandular differentiation or mucin production expressing in different patterns and degrees of differentiation. </p><p>This article brings a broad view over lung adenocarcinoma, for further details on each subtype, please refer to the specific articles listed below. </p><h4>Terminology</h4><p>In 2011, the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS) introduced a new classification and terminology for adenocarcinoma of the lung, which is now divided into:</p><ul>
-<a href="/articles/preinvasive-adenocarcinoma-lesion-of-the-lung">preinvasive adenocarcinoma lesions</a>: no invasion</li>- +<a href="/articles/preinvasive-adenocarcinoma-lesion-of-the-lung">preinvasive adenocarcinoma lesions</a><ul>
-<a href="/articles/minimally-invasive-adenocarcinoma-of-the-lung-1">minimally invasive adenocarcinoma</a>: ≤5 mm invasion</li>- +<a href="/articles/atypical-adenomatous-hyperplasia-of-the-lung">atypical adenomatous hyperplasia (AAH)</a> </li>
- +<li><a href="/articles/adenocarcinoma-in-situ-of-the-lung">adenocarcinoma in situ (AIS)</a></li>
- +</ul>
- +</li>
- +<li><a href="/articles/minimally-invasive-adenocarcinoma-of-the-lung-1">minimally invasive adenocarcinoma</a></li>
- +<li>invasive adenocarcinoma <ul>
-<a href="/articles/adenocarcinoma-of-the-lung">invasive adenocarcinoma</a>: >5 mm invasion</li>-</ul><p>For invasive adenocarcinoma, further subcategorization is recommended according to the dominant histologic pattern. Both mucinous and non-mucinous adenocarcinomas typically consist of a mixture of histologic patterns (all previously known as "mixed subtype", a now-defunct category), but reporting of the predominant subtype is specifically recommended for non-mucinous lesions <sup>1</sup>:</p><ul>- +<a href="/articles/lepidic-predominant-adenocarcinoma-of-the-lung-3">lepidic predominant adenocarcinoma of the lung</a> <ul><li>formerly non-mucinous <a href="/articles/adenocarcinoma-in-situ-minimally-invasive-adenocarcinoma-and-invasive-adenocarcinoma-of-lung">bronchioloalveolar carcinoma (BAC)</a>
- +</li></ul>
- +</li>
- +<li><a href="/articles/acinar-predominant-adenocarcinoma-of-the-lung-3">acinar predominant adenocarcinoma of the lung</a></li>
- +<li><a href="/articles/papillary-predominant-adenocarcinoma-of-the-lung-2">papillary predominant adenocarcinoma of the lung</a></li>
- +<li><a href="/articles/micropapillary-predominant-adenocarcinoma-of-the-lung">micropapillary predominant adenocarcinoma of the lung</a></li>
- +<li><a href="/articles/solid-predominant-with-mucin-adenocarcinoma-of-lung">solid predominant with mucin</a></li>
- +</ul>
- +</li>
- +<li>variants of invasive adenocarcinoma <ul>
- +<li>
- +<a href="/articles/invasive-mucinous-adenocarcinoma-of-the-lung-1">invasive mucinous adenocarcinoma</a> <ul><li>formerly mucinous BAC</li></ul>
- +</li>
- +<li>colloid</li>
- +<li>fetal (low and high grade)</li>
- +<li>enteric</li>
- +</ul>
- +</li>
- +</ul><h4>Epidemiology</h4><p>It is now considered the most common histological subtype in terms of prevalence.</p><h4>Clinical presentation</h4><p>Early symptoms are fatigue with mild dyspnoea followed by a chronic cough and <a href="/articles/haemoptysis-1">haemoptysis</a> at a later stage.</p><h4>Pathology</h4><p>Lung adenocarcinoma is primarily categorized on the basis of histopathologic evaluation, although testing for genetic mutations (e.g. <em>EGFR</em>, <em>KRAS</em>) is becoming increasingly important for consideration of therapy <sup>1</sup>.</p><ul>
- +<li>
- +<a href="/articles/preinvasive-adenocarcinoma-lesion-of-the-lung">preinvasive adenocarcinoma lesions</a> <ul>
- +<li>
- +<a href="/articles/atypical-adenomatous-hyperplasia-of-the-lung">atypical adenomatous hyperplasia (AAH)</a> <ul>
- +<li>localised small cell proliferation, usually ≤0.5 cm</li>
- +<li>histological pattern: a focal proliferation of mildly to moderately atypical type II pneumocytes and/or Clara cells that line along the alveolar walls, alveolar septae, or respiratory bronchiole</li>
- +</ul>
- +</li>
- +<li>
- +<a href="/articles/adenocarcinoma-in-situ-of-the-lung">adenocarcinoma in situ (AIS)</a> <ul>
- +<li>localised adenocarcinoma of ≤3 cm </li>
- +<li>histological pattern: no growth pattern other than lepidic, with neoplastic cells along the alveolar structures but without stromal, vascular, or pleural invasion, and no features of necrosis </li>
- +<li>has a number of subtypes: the most common subtype is non-mucinous and, rarely, mucinous or mixed subtypes</li>
- +</ul>
- +</li>
- +</ul>
- +</li>
- +<li>
- +<a href="/articles/minimally-invasive-adenocarcinoma-of-the-lung-1">minimally invasive adenocarcinoma</a><ul>
- +<li>localised adenocarcinoma of ≤3 cm</li>
- +<li>histological pattern: either pure lepidic or predominant lepidic growth pattern, with neoplastic cells along the alveolar structures with ≤5 mm of stromal invasion. These lesions should not show necrosis, lymphatic, vascular, or pleural invasion. </li>
- +<li>three histopathological subtypes are recognised:<ul>
- +<li>non-mucinous: by far the most common subtype </li>
- +<li>mucinous: goblet cell (mucus-secreting), often multicentric, rare</li>
- +<li>mixed</li>
- +</ul>
- +</li>
- +</ul>
- +</li>
- +<li>invasive adenocarcinoma (>5 mm invasion) - further subcategorization is recommended according to the dominant histologic pattern<ul>
-<a href="/articles/lepidic-predominant-adenocarcinoma-of-the-lung-3">lepidic predominant adenocarcinoma of the lung</a>: formerly non-mucinous <a href="/articles/adenocarcinoma-in-situ-minimally-invasive-adenocarcinoma-and-invasive-adenocarcinoma-of-lung">bronchioloalveolar carcinoma (BAC)</a> pattern, with > 5 mm invasion</li>- +<a href="/articles/lepidic-predominant-adenocarcinoma-of-the-lung-3">lepidic predominant adenocarcinoma of the lung</a> <ul><li>formerly non-mucinous <a href="/articles/adenocarcinoma-in-situ-minimally-invasive-adenocarcinoma-and-invasive-adenocarcinoma-of-lung">bronchioloalveolar carcinoma (BAC)</a>
- +</li></ul>
- +</li>
-<li><a title="Micropapillary predominant adenocarcinoma of the lung" href="/articles/micropapillary-predominant-adenocarcinoma-of-the-lung">micropapillary predominant adenocarcinoma of the lung</a></li>- +<li><a href="/articles/micropapillary-predominant-adenocarcinoma-of-the-lung">micropapillary predominant adenocarcinoma of the lung</a></li>
-</ul><p>Variants of invasive adenocarcinoma:</p><ul>- +</ul>
- +</li>
- +<li>variants of invasive adenocarcinoma <ul>
-<a href="/articles/invasive-mucinous-adenocarcinoma-of-the-lung-1">invasive mucinous adenocarcinoma</a> (formerly mucinous BAC)</li>- +<a href="/articles/invasive-mucinous-adenocarcinoma-of-the-lung-1">invasive mucinous adenocarcinoma</a> <ul><li>formerly mucinous BAC</li></ul>
- +</li>
- +</ul>
- +</li>
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