Pathologic T Descriptor of Nonmucinous Lung Adenocarcinomas Now Based on Invasive Tumor Size: How Should Pathologists...

Area of Science:

• Oncology
• Pathology
• Radiology

Background:

• The American Joint Committee on Cancer staging manual (8th ed.) now uses invasive component size for nonmucinous lung adenocarcinomas (nmLACAs).
• Tumor size is determined by direct gross or microscopic measurement.
• A calculated invasive size based on invasive growth patterns is an alternative proposed method.

Purpose of the Study:

• To compare radiologic and pathologic assessments of invasive tumor size in nmLACAs.
• To evaluate the concordance between direct microscopic and calculated pathologic invasive tumor measurements.
• To assess the accuracy of computed tomography (CT) scan measurements against pathologic assessments.

Main Methods:

• Retrospective review of 112 resected nmLACAs with a part-solid appearance on CT scans.
• Comparison of direct microscopic pathologic invasive measurements with calculated pathologic invasive measurements.
• Comparison of CT scan invasive measurements with direct pathologic measurements.

Main Results:

• Median direct microscopic and calculated pathologic invasive measurements were not significantly different.
• Median CT invasive measurements were 0.26 cm larger than median direct pathologic measurements (P < .001).
• Pathologic calculated invasive tumor measurements are comparable to direct microscopic measurements.

Conclusions:

• Pathologic calculated invasive tumor measurements are a reliable alternative to direct microscopic measurements for nmLACAs.
• The findings support the use of calculated invasive tumor size by pathologists when necessary.
• CT scan measurements may overestimate invasive tumor size compared to direct pathologic assessment.