A 58-year-old man with a 40-year history of smoking presents with chronic cough and hemoptysis. Bronchoscopy reveals a nodular lesion in the left main bronchus. Biopsy shows replacement of normal ciliated pseudostratified columnar epithelium with stratified squamous epithelium. The squamous epithelium shows increased nuclear-to-cytoplasmic ratio, irregular nuclear membranes, and coarse chromatin in scattered cells. What is the most likely diagnosis?
A. Metaplasia of the bronchial epithelium
B. Dysplasia of the bronchial epithelium
C. Anaplastic carcinoma of the lung
D. Squamous cell carcinoma of the lung
Explanation
Clinical Interpretation
The biopsy findings show two distinct pathological processes occurring simultaneously in the bronchial epithelium.
Metaplasia Component
Key Point
The replacement of ciliated pseudostratified columnar epithelium (normal respiratory epithelium) with stratified squamous epithelium is metaplasia — a reversible adaptive change in which one differentiated cell type is replaced by another.
This occurs in response to chronic irritation from smoking
The squamous epithelium is better suited to withstand chemical irritants
This change is potentially reversible if the stimulus (smoking) is removed
Dysplasia Component
Key Point
The presence of increased nuclear-to-cytoplasmic ratio, irregular nuclear membranes, and coarse chromatin represents dysplasia — a pre-malignant change characterized by loss of uniformity and architectural disorganization.
High-YieldNEET PG
Dysplasia is graded as:
Mild: confined to lower third of epithelium
Moderate: extends to middle third
Severe: extends to upper third (carcinoma in situ if full thickness)
Why This Is Dysplasia, Not Carcinoma
Clinical Pearl
The key distinction is that dysplasia remains confined within the epithelium — there is no invasion through the basement membrane. Carcinoma requires invasion into underlying stroma.
Metaplasia vs. Dysplasia Comparison
Table
Feature
Metaplasia
Dysplasia
Definition
Replacement of one differentiated cell type with another
Loss of uniformity and architectural disorganization
Do not confuse metaplasia with dysplasia. Metaplasia alone is an adaptation; dysplasia is a pre-malignant change. The presence of nuclear atypia (irregular membranes, coarse chromatin) is the key feature that elevates this from simple metaplasia to dysplasia.
Clinical Significance
Mnemonic
METAPLASIA = Adaptation; DYSPLASIA = Atypia
Metaplasia in the lung is common in smokers and is initially protective
However, when dysplastic changes appear, this indicates field cancerization and increased risk of malignant transformation
Continued smoking in the presence of dysplasia significantly increases the risk of progression to invasive carcinoma
Why Not Carcinoma?
Carcinoma requires invasion through the basement membrane into the underlying stroma. The question states the changes are in the epithelium — this is dysplasia, not invasive cancer.
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