Multicentricity in Lung Cancer
Multicentricity is characteristic of bronchoalveolar carcinoma (option c), now reclassified as a subtype of lung adenocarcinoma with lepidic growth pattern.
Understanding Multicentricity in Lung Cancer
Multicentricity refers to the presence of multiple tumor foci arising simultaneously in different locations within the lungs. This characteristic is strongly associated with what was formerly known as bronchioloalveolar carcinoma (BAC), which has been reclassified in current terminology.
Historical Context and Current Classification
The term bronchioloalveolar carcinoma (BAC) has been abandoned in newer classification systems due to inconsistent usage 1. However, the entity it described still exists and is now recognized under different terminology:
- What was formerly known as BAC is now classified as:
- Adenocarcinoma in situ (AIS)
- Minimally invasive adenocarcinoma (MIA)
- Lepidic predominant adenocarcinoma (LPA) 1
Distinctive Features of Multifocal Lung Adenocarcinoma
Multifocal lung adenocarcinomas (formerly BAC) present with several distinctive characteristics:
- Multiple ground-glass opacities (GGOs) or part-solid nodules on CT imaging 1
- May develop solid components over time
- Can present as few or numerous lesions
- May show an infiltrative pattern confined to a segment/lobe or diffusely in the lung parenchyma (pneumonic type) 1
- Decreased propensity for nodal or systemic spread compared to other lung cancers 1
- Increased propensity to develop additional pulmonary foci 1
Epidemiology and Risk Factors
These multifocal adenocarcinomas have distinctive epidemiological features:
- More common in women
- Higher prevalence in non-smokers compared to other lung cancer types 1
- Patients with multifocal adenocarcinoma have a higher chance of developing subsequent lesions 1
Staging and Classification
The American College of Chest Physicians (ACCP) panel recommends:
- Using the T(m) designation for patients with multifocal lung cancer
- Classifying by the highest T stage of one focus with the number of tumors in parentheses
- Example: Four GGO lesions all measuring <2 cm would be classified as T1a(4) 1
- The N and M designations apply to all multiple tumor foci collectively 1
Differentiating from Other Lung Cancer Types
Multicentricity is not a typical feature of the other options listed:
- Squamous cell carcinoma typically presents as a central, endobronchial mass
- Small cell lung cancer usually presents as a central mass with early metastasis
- Bronchial adenocarcinoma (conventional type) typically presents as a solitary peripheral nodule
- Bronchial carcinoid tumors are usually solitary, well-defined nodules 1
Clinical Implications
The multifocal nature of these adenocarcinomas has important clinical implications:
- Better prognosis compared to other lung cancers with less lymph node involvement and systemic spread 1
- Patients with solitary, small, peripheral lesions meeting strict BAC criteria have been reported to have 100% 5-year survival rates 2
- Different therapeutic approach may be needed compared to other lung cancers
- May be more responsive to EGFR-targeted therapies 3
Pathophysiology of Multicentricity
Research suggests that multicentricity in these adenocarcinomas may be due to:
- Multiclonal origin (multiple primary tumors arising independently) rather than intrapulmonary spread 4
- This explains why these tumors can present in multiple lobes simultaneously without following typical metastatic patterns
This multiclonal origin distinguishes these tumors from other lung cancers and explains their unique clinical behavior and better prognosis despite multifocal presentation.