Do any lung cancers present as ground‑glass opacity on thin‑section CT?

Yes, Several Lung Cancers Present as Ground-Glass Opacity

Adenocarcinoma in situ (AIS, formerly bronchioloalveolar carcinoma), minimally invasive adenocarcinoma (MIA), and invasive adenocarcinoma with lepidic growth pattern all commonly present as ground-glass opacities (GGO) on thin-section CT. 1

Primary Malignancies That Present as GGO

Adenocarcinoma Spectrum

• Adenocarcinoma in situ (AIS) appears radiographically as pure ground-glass opacity without central densities, representing the non-invasive end of the adenocarcinoma spectrum 1
• Minimally invasive adenocarcinoma (MIA) presents as part-solid nodules with a central density (representing the invasive component ≤5 mm) surrounded by ground-glass opacity 1
• Invasive adenocarcinoma with lepidic predominance manifests as larger part-solid nodules where the solid component exceeds 5 mm 1

Histologic Characteristics

• These tumors demonstrate lepidic (surface) growth along alveolar septa, which creates the ground-glass appearance on imaging 1
• The non-mucinous type shows type 2 alveolar pneumocyte or bronchiolar cell differentiation with CK7 and TTF-1 positivity 1
• The mucinous pattern resembles colonic differentiation with CK7-negative, CK20-positive, and TTF-1-negative immunophenotype 1

Size and Morphology Correlations

Pure Ground-Glass Nodules

• Small (<10 mm) pure ground-glass nodules usually represent atypical adenomatous hyperplasia (AAH, a premalignant lesion) or AIS 1
• Pure GGO nodules ≥6 mm warrant surveillance as they carry substantial malignancy risk 1, 2

Part-Solid Nodules

• Part-solid nodules with solid components ≥6 mm have high likelihood of invasive adenocarcinoma 1
• The size of the solid component correlates more strongly with prognosis than overall nodule size 1
• Solid components >5 mm correlate with substantial likelihood of local invasion and potential for nodal metastases 1

Critical Diagnostic Pitfalls

PET Scanning Limitations

• PET scanning has poor sensitivity (47-62%) for detecting malignancy in subsolid nodules and should not be relied upon to exclude cancer 1, 3
• FDG uptake inversely correlates with the extent of lepidic component—the more ground-glass appearance, the less PET avidity 1
• False-negative PET results are common in lepidic-predominant tumors 1

Biopsy Challenges

• CT-guided needle biopsy has only 67% sensitivity for identifying malignancy in subsolid nodules, with lower sensitivity for pure ground-glass nodules 1
• AIS or MIA cannot be reliably diagnosed from needle biopsy alone—entire lesion evaluation is required 1

Prognosis and Clinical Significance

Excellent Outcomes When Treated Appropriately

• Patients with completely excised solitary AIS have nearly 100% 5- and 10-year survival 1, 2
• MIA with ≤5 mm central invasive component shows no lymph node metastases and nearly 100% survival when resected 1
• Even malignant GGOs have 100% overall survival when treated as stage 1 lesions due to their indolent behavior 3, 2

Growth Patterns

• Mean time for detectable growth in subsolid malignant nodules ranges from 425-715 days depending on measurement method 3
• Documented growth in a GGO strongly suggests malignancy and warrants aggressive evaluation 3, 2

Management Implications

Surveillance Requirements

• Pure ground-glass nodules ≥6 mm require initial follow-up at 6-12 months, then continued surveillance for 5 years 1, 2
• Part-solid nodules with solid component ≥6 mm warrant short-term follow-up at 3-6 months to evaluate persistence 1
• Thin-section CT (≤1.5 mm slices) is mandatory for accurate characterization 2

Indications for Intervention

• Development of solid component, documented growth ≥2 mm, or increasing density mandates surgical resection or biopsy 1, 2
• Part-solid nodules with solid component >8 mm, lobulated margins, or cystic components warrant PET/CT, biopsy, or resection 1

Multifocal Disease

• Multiple bilateral ground-glass or part-solid nodules of similar size without mediastinal adenopathy strongly suggest separate primary lung adenocarcinomas rather than metastases 1, 4
• Limited resection of all suspicious lesions is recommended when feasible, given excellent prognosis and need to preserve lung parenchyma 1