A 60-year-old smoker has a peripheral lung mass. Biopsy shows gland-forming cells with intracellular mucin positivity and TTF-1 positivity. The most likely histological type is:
- A Adenocarcinoma ✓
- B Squamous cell carcinoma
- C Large cell carcinoma
- D Small cell carcinoma
Correct answer: A. Adenocarcinoma
Explanation
Peripheral location, glandular differentiation with mucin, and TTF-1 (thyroid transcription factor-1) positivity are hallmarks of pulmonary adenocarcinoma. TTF-1 is expressed in type II pneumocytes and Clara cells and is positive in ~75% of lung adenocarcinomas and all small cell carcinomas (but small cell lacks gland formation). Squamous cell carcinoma is central, p40/p63-positive, and TTF-1 negative.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.