Lung adenocarcinoma is the most common type of lung cancer, accounting for approximately 40% of all lung cancers. It is typically peripheral in location and favors the upper lobes. It is the most common histological type in non-smokers, women, and younger patients. It can harbor targetable mutations such as EGFR, ALK, ROS1, and KRAS, offering targeted therapy options. Prognosis depends on subtype and stage — lepidic predominant has the best prognosis while solid predominant has the worst. Five-year survival is approximately 90% in stage IA and less than 5% in stage IV.
Age Range
40-80
Peak Age
65
Gender
Female predominant
Prevalence
Common
Adenocarcinoma originates from type II pneumocytes and Clara cells in the peripheral airways. In the lepidic growth pattern, tumor cells spread along existing alveolar walls — this appears as ground-glass opacity because the alveoli remain air-filled while their walls thicken. As the invasive component develops, alveolar structures are destroyed and a solid nodule forms — causing soft tissue attenuation on CT. The tumor's desmoplastic stromal reaction creates fibrosis in the surrounding parenchyma producing spiculated margins — these fibrotic bands appear as linear opacities on CT. Air bronchograms form when patent bronchi within the tumor are surrounded by solid tumor tissue. Due to intense neovascularization, it shows prominent arterial phase enhancement and demonstrates high FDG uptake on PET-CT.
In a peripheral part-solid nodule, the combination of a solid core (invasive component) surrounded by a ground-glass halo (lepidic component) with spiculation radiating from the solid component is the signature finding of adenocarcinoma. This triple combination (peripheral + part-solid + spiculated) distinguishes adenocarcinoma from other lung cancers with high specificity.
Peripheral, spiculated solid nodule or mass. Typically in upper lobes, subpleural region. Size ranges from 8 mm to >10 cm. Spiculated margin reflects desmoplastic infiltration of tumor into surrounding parenchyma.
Report Sentence
A ___ mm spiculated peripheral solid nodule/mass in the right/left upper lobe is identified, and primary lung adenocarcinoma should be the primary consideration.
Ground-glass opacity (GGO): All or part of the nodule shows ground-glass attenuation. Pure ground-glass nodule suggests lepidic predominant adenocarcinoma (AIS/MIA). In part-solid nodules, the solid component reflects invasive growth while the ground-glass component reflects lepidic growth. Prognosis worsens as the solid component ratio increases.
Report Sentence
The nodule demonstrates a ___ mm solid component with surrounding ground-glass opacity (part-solid nodule) consistent with invasive adenocarcinoma; the solid component ratio has prognostic significance.
Heterogeneous enhancement on contrast-enhanced CT. The solid component enhances markedly (40-80 HU increase) while ground-glass component and necrotic areas do not enhance. Central necrosis is common in large masses. Enhancement pattern reflects tumor vascularity.
Report Sentence
The mass demonstrates heterogeneous enhancement on contrast-enhanced CT with marked enhancement of the solid component and non-enhancing central necrotic areas.
Air bronchograms: Visualization of air-filled bronchi within solid tumor tissue. Particularly prominent in lepidic and mucinous subtypes. Can be distinguishing from pneumonia in consolidation-pattern adenocarcinoma — persistent consolidation + air bronchograms favor malignancy.
Report Sentence
Air bronchograms are identified within the consolidation area, and in the presence of persistent consolidation, adenocarcinoma (particularly mucinous type) should be considered in the differential diagnosis.
Pleural tail sign: Fine linear opacity (1-2 mm thickness) extending from the nodule to the pleural surface. Reflects desmoplastic reaction extending to the pleural surface. Has 70-80% positive predictive value for malignancy but can also be seen in benign lesions.
Report Sentence
A pleural tail sign extending from the nodule to the pleural surface is identified, a finding consistent with peripheral adenocarcinoma.
High FDG uptake: SUVmax in solid adenocarcinoma is typically >2.5, often ranging 5-15. Metabolic activity increases with increasing invasive component. Pure ground-glass nodules (AIS/MIA) may have low or negative FDG uptake — a false-negative pitfall. Critical for mediastinal/hilar lymph node and distant metastasis staging.
Report Sentence
The lung nodule/mass demonstrates intense FDG uptake on PET-CT (SUVmax: ___) consistent with primary lung adenocarcinoma; mediastinal/hilar lymph nodes and distant metastases should be evaluated.
Diffusion restriction on DWI: High signal in solid tumor component (b=800-1000), low signal on ADC map. ADC value is typically <1.2 × 10⁻³ mm²/s. Prominent in invasive component with high cellularity. Necrotic areas do not show diffusion restriction.
Report Sentence
The mass demonstrates diffusion restriction on DWI (ADC: ___ × 10⁻³ mm²/s) consistent with a malignant lesion with high cellularity.
Bubble-like lucencies: Small, round air-density areas within the nodule. Reflect patent small bronchioles or alveolar spaces persisting within tumor tissue. Characteristic of the lepidic growth pattern of adenocarcinoma and a distinguishing feature from squamous cell carcinoma.
Report Sentence
Bubble-like lucencies within the nodule are identified, consistent with adenocarcinoma demonstrating a lepidic growth pattern.
Criteria
Pure ground-glass nodule or minimal solid component (≤5 mm). Tumor cells spread along existing alveolar walls without stromal/vascular/pleural invasion. AIS ≤3 cm, MIA ≤3 cm with ≤5 mm invasion.
Distinct Features
Pure GGN or minimal solid component on CT, very slow growth (volume doubling time >800 days), low/negative FDG uptake on PET-CT, 100% survival after surgery. Sublobar resection sufficient.
Criteria
Most common invasive subtype. Forms glandular/acinar structures. Solid nodule or mass, typically with spiculated margins.
Distinct Features
Solid spiculated nodule on CT, marked enhancement, high FDG uptake on PET-CT (SUVmax 3-10). Intermediate prognosis — 5-year survival 60-70%.
Criteria
Papillary structures (fibrovascular core + tumor cells). Moderately differentiated.
Distinct Features
Solid or part-solid nodule on CT, imaging findings similar to acinar type. May have lepidic component (peripheral GGO). High rate of EGFR mutation.
Criteria
Papillary structures without fibrovascular cores. High invasive potential, early lymphangitic spread.
Distinct Features
Solid nodule on CT, early mediastinal/hilar lymphadenopathy, frequent vascular invasion. High FDG uptake on PET-CT. Poor prognosis — 5-year survival 40-50%.
Criteria
Growth in solid sheets, minimal glandular differentiation. High grade, aggressive.
Distinct Features
Large solid mass on CT, frequent necrosis, rapid growth. Very high FDG uptake on PET-CT (SUVmax >10). Worst prognosis — 5-year survival 30-40%. Can be confused with small cell carcinoma.
Distinguishing Feature
Squamous cell carcinoma is typically central, cavitation is common (30-80%), and shows endobronchial growth pattern. Adenocarcinoma is distinguished by peripheral location, ground-glass component, and spiculated margins. Cavitation is rare in adenocarcinoma (5-10%).
Distinguishing Feature
Mucinous adenocarcinoma shows consolidation pattern (pneumonia mimic), CT angiogram sign is positive (enhancing vessels within consolidation), tends to be multifocal/bilateral. Conventional adenocarcinoma presents as a single nodule/mass.
Distinguishing Feature
Metastases are typically multiple, bilateral, round, smooth-margined nodules. Lower lobe predominant (hematogenous spread). Spiculation, ground-glass component, and air bronchograms are rare. Known extrathoracic malignancy history is distinguishing.
Distinguishing Feature
Hamartoma contains fat (-40 to -120 HU) and/or popcorn calcification — findings not seen in adenocarcinoma. Hamartoma is smooth-margined, round, slow-growing, and has low FDG uptake on PET-CT.
Distinguishing Feature
Granuloma is typically <10 mm, smooth-margined, with central/diffuse/laminar calcification. Stable size (no change on serial CT >2 years). FDG uptake on PET-CT is usually low (except active granulomatous disease). No spiculation or ground-glass component.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
specialist-referralSurgical resection is curative in early-stage (I-II) adenocarcinoma — lobectomy + mediastinal lymph node dissection is standard treatment. Sublobar resection may be sufficient for lepidic predominant type (AIS/MIA). Advanced stage (III-IV) requires chemotherapy, radiation, and targeted therapy (if EGFR/ALK/ROS1 mutation present). Immunotherapy (based on PD-L1 expression) has been added to standard treatment. Multidisciplinary tumor board evaluation is required. EGFR, ALK, ROS1, KRAS, BRAF mutation testing and PD-L1 expression should be performed on tissue samples.
Lung adenocarcinoma is treated with surgery, chemotherapy, targeted therapy, and immunotherapy. Molecular markers such as EGFR, ALK, ROS1 guide treatment selection. Surgical resection is curative in early stages.