Preinvasive adenocarcinoma lesion of the lung

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Preinvasive lesions for lung adenocarcinoma are a category of small non-invasive lung lesions which are closely related to adenocarcinoma of the lung. They may represent a spectrum of premalignant to low-grade malignant lesions.

The category includes two types of lesions:

Terminology

In 2011, the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society introduced a new classification and terminology for adenocarcinoma of the lung.  In addition to retiring the term "bronchoalveolar carcinoma (BAC)", the 2011 update officially recognized "adenocarinoma in situ" as a distinct entity with excellent clinical prognosis.

Pathology

Atypical adenomatous hyperplasia and adenocarcinoma in situ may be considered a spectrum of premalignant disease:

  • atypical adenomatous hyperplasia is typically a small (≤5 mm) lesion with mild-moderate cellular atypia
  • adenocarcinoma in situ lesions are larger, yet still ≤3 cm and demonstrating purely lepidic growth (no invasion)

Between these two, intermediate cases may be difficult to distinguish .

Findings which indicate more profound genetic alteration, such as non-lepidic (e.g. papillary) growth patterns or tumor necrosis, indicate a more advanced grade of disease.

Radiographic features

Preinvasive lesions of adenocarcinoma are generally not evident by x-ray.

On CT, both atypical adenomatous hyperplasia and adenocarcinoma in situ typically manifest as a round, purely ground glass opacity.

  • usually a single opacity
    • multiple lesions more common with AIS
  • "clear" periphery (>85%)
    • lobuation, spiculation, pleural indentation are seen in both AAH and AIS, but less common (<21%)
  • vacuole sign - internal gas-appearing lucency <5 mm
    • specific to AIS in one 2017 radiology/pathology correlative study (n=80 lesions)