A 65-year-old never-smoker woman has a lung adenocarcinoma with a lepidic growth pattern on histology and EGFR exon 19 deletion on molecular testing. The lepidic pattern is defined as:
- A Growth of neoplastic cells along pre-existing alveolar walls (alveolar scaffold preserved) without stromal invasion, vascular invasion, or pleural invasion ✓
- B Central bronchogenic carcinoma with endobronchial polypoid growth
- C Diffuse alveolar damage pattern with hyaline membranes containing adenocarcinoma cells
- D Solid nests of cells with mucin production replacing alveolar airspaces
Correct answer: A. Growth of neoplastic cells along pre-existing alveolar walls (alveolar scaffold preserved) without stromal invasion, vascular invasion, or pleural invasion
Explanation
The lepidic pattern (from Greek lepis = scale, referring to butterfly wing growth along structures) in adenocarcinoma describes tumor cells growing along intact alveolar walls in a non-invasive manner, preserving the alveolar framework. Adenocarcinoma in-situ (AIS) is purely lepidic; minimally invasive adenocarcinoma has ≤5 mm invasion. Invasive adenocarcinoma may have a predominant lepidic component. This pattern is more common in EGFR-mutant adenocarcinomas and carries a better prognosis than solid, micropapillary, or acinar patterns.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.