Growth pattern-based grading of pulmonary adenocarcinoma-Analysis of 534 cases with comparison between observers and survival analysis.
OBJECTIVES
The 2015 WHO classification of pulmonary adenocarcinoma recommends recording observed architectural growth patterns in 5% increments for resected tumors, and determining the predominant growth pattern, which seems to be prognostic. There is debate over the best way to implement pattern-based grading, and whether such systems are reproducible.


MATERIALS AND METHODS
534 resected adenocarcinomas were reviewed by 2 pulmonary pathologists to determine predominant pattern and percentages of all observed patterns. Three different grading schemes were applied based on predicted prognosis scores: score 1 (lepidic), score 2 (acinar/papillary), and score 3 (solid/micropapillary/cribriform). Mucinous tumors were separately evaluated as both scores 2 and 3 since their prognosis is more ambiguous. The first grading scheme used the score of the predominant pattern; the second used the worst observed pattern score; and the third scored tumors with ≥80% lepidic growth as 1, tumors with ≥20% of any score 3 pattern(s) as 3, and all remaining as 2.


RESULTS
The predominant pattern assigned by each observer was an exact match in 51.7% of cases, a "close match" in 27.3% (same prognosis score), and a mismatch in 21%. Predominant pattern determined by both observers showed significant stratification of overall and progression-free survival (OS and PFS, respectively). All 3 grading schemes showed a significant difference in OS and PFS determined by both observers; but the worst score scheme provided suboptimal results, likely due to a very small score 1 group, and this scheme did not maintain significance on multivariable analysis. Survival differences for all grading schemes maintained significance whether mucinous was considered score 2 or 3, but mucinous tumors trended towards poor survival.


CONCLUSION
Pattern-based grading has prognostic significance in pulmonary adenocarcinoma. Interobserver variation is present, but two observers were able to predict significant differences in OS and PFS using various pattern-based grading schemes.
['Boland|J M|JM|', 'Wampfler|J A|JA|', 'Yang|P|P|', 'Yi|E S|ES|']
D000230:Adenocarcinoma D000328:Adult D000368:Aged D000369:Aged, 80 and over D063646:Carcinogenesis D048708:Cell Growth Processes D015331:Cohort Studies D005260:Female D005500:Follow-Up Studies D006801:Humans D008175:Lung Neoplasms D008297:Male D008875:Middle Aged D009367:Neoplasm Staging D015588:Observer Variation D011237:Predictive Value of Tests D011379:Prognosis D016019:Survival Analysis
Grading Pulmonary adenocarcinoma Predominant pattern