Comparison between CT tumor size and pathological tumor size in frozen section examinations of lung adenocarcinoma

Abstract

Objective: We examined the appropriate measurement for pathological tumor size by comparing radiological and pathological tumor size of resected lung adenocarcinoma in FSE.

Materials and methods: We reviewed records of 59 resected specimens of lung adenocarcinoma for FSE from January to December 2008. Specimens were well-inflated with saline by using an injector before cutting into segments. After selecting the tumor segment of maximal diameter, we compared three ways of measuring pathological tumor size by using paired t-test: (I) macroscopic tumor size (MTS), measured with a metal straight ruler, (II) microscopic frozen section tumor size (FSTS), and (III) microscopic paraffin section tumor size (PSTS). We compared each discrepancy rate (DR) [DR=(CT tumor size-pathological tumor size)/CT tumor size×100] (%) between tumors that were air-containing type and solid-density type on CT scans, and also compared the tumors with lepidic component rates (LCR) ≥50% and LCR <50%, by using Mann-Whitney U-tests.

Results: FSE could diagnose malignancy with 100% accuracy. The mean CT tumor size was 18.36mm, and the mean pathological tumor sizes (MTS, FSTS, and PSTS) were 17.81, 14.29, and 14.23mm, respectively. FSTS and PSTS were significantly smaller than CT tumor size (p<0.001). The DR calculated with PSTS was significantly larger in air-containing than in solid-density tumors, and also larger in LCR ≥50% than in LCR <50% tumors.

Conclusion: FSE with the inflation method diagnosed malignancy with 100% accuracy. The lung specimen must be sufficiently inflated to prevent tissue shrinking, and we propose MTS as the definition for pathological tumor size in FSE. The greater discordance observed between CT tumor size and microscopic tumor size was assumed to be due to shrinkage of the lepidic component in the tumor.

Keywords: Adenocarcinoma; CT tumor size; Frozen section examinations; Inflation method; Lepidic; Lung cancer; Pathological tumor size.