Adenocarcinoma of the lung
Adenocarcinoma of the lung is one of the non-small cell carcinomas of the lung and is a malignant tumor with glandular differentiation or mucin production. This tumor exhibits various patterns and degrees of differentiation, including lepidic, acinar, papillary, micropapillary and solid with mucin formation 1.
It is now considered the most common histological subtype in terms of prevalence.
Early symptoms are fatigue with mild dyspnea followed by chronic cough and hemoptysis at a later stage.
Classification of the tumor subtype is based on the estimate of the percentage of histologic patterns and the predominant subtype. The terminology of mixed subtype is to be avoided:
- lepidic predominant (formerly non-mucinous bronchioloalveolar carcinoma (BAC) pattern, with >5 mm invasion)
- acinar predominant
- papillary predominant
- micropapillary predominant
- solid predominant with mucin
Variants of invasive adenocarcinoma
- invasive mucinous adenocarcinoma (formerly mucinous BAC)
- fetal (low and high grade)
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, sub-solid or solid.1,2
Histologically, the ground-glass attenuation corresponds to a lepidic growth pattern and the solid component correspond to invasive patterns. Hence the preinvasive category of AIS, MIA, and the invasive subtype of LPA is often seen as ground glass nodule or sub-solid nodule with a predominant ground-glass component. On the other hand, the remaining invasive subtypes of adenocarcinoma is usually a solid nodule but may also subsolid and only occasionally seen as ground glass nodule 1,2.
Invasive mucinous adenocarcinoma subtype (formerly mucinous BAC) can have a variable appearance ranging from consolidation, air bronchograms or seen as multifocal subsolid nodules or masses 2.
Treatment and prognosis
Recommendation for follow-up of solid nodules is as per Fleischner Society guidelines. Recommendation for ground glass or subsolid nodules has recently been proposed, please consult Naidich et article - Recommendations for the management of sub-solid pulmonary nodules detected at CT: a statement from the Fleischner Society 3.