Unifocal Invasive Lobular Carcinoma: Tumor Size Concordance Between Preoperative Ultrasound Imaging and Postoperative Pathology

Preoperative ultrasound imaging can provide tumor size measurements. In invasive lobular carcinoma (ILC), it is unclear whether the concordance in tumor size stage (T stage) between the ultrasound and pathologic findings is dependent on the tumor T stage itself. From a cohort of 128 cases of ILC, 66 unifocal ILC cases were analyzed. The concordance between the clinical tumor size stage from ultrasound (cT) and the pathology tumor size stage (pT) varied with pT stage (P =.0003, Fisher's exact test), with the greatest concordance rate of 95.7% (95% confidence limit, 85.2%-99.5%) observed for pT1 tumors. Caution is warranted when using ultrasonography to stage ILCs larger than pT1. Background: We systematically analyzed the extent of disease in unifocal invasive lobular carcinoma (ILC) using ultrasonography, with the histopathologic findings as the reference standard. Patients and Methods: In the present single-institution retrospective study, 128 cases of ILC were identified during a 5-year period. After exclusions, the analyzed cohort included 66 cases. Ultrasound measurements of the tumor extent along 3 axes were obtained. The tumor size was determined as the largest extent among the 3 axes and the tumor volume by ellipsoidal approximation. Pathology review provided the tumor size and volume. Correlation and regression analyses of tumor size and volume from the ultrasound and pathologic examinations were performed. The tumor stage from the ultrasound and pathologic examinations were used for the concordance analyses. Results: The median and quartiles (Q1, Q3) of tumor size from ultrasonography and pathology were 12.5 mm (Q1, 9 mm; Q3, 19 mm) and 17 mm (Q1, 12 mm; Q3, 25 mm), respectively. The corresponding data for tumor volume were 0.52 cm ³ (Q1, 0.18 cm ³ ; Q3, 1.92 cm ³ ) and 1.04 cm ³ (Q1, 0.45 cm ³ ; Q3, 2.49 cm ³ ). The ultrasound measurements correlated with the pathology-reported tumor size (Spearman ρ = 0.678; P <.0001) and volume (Spearman ρ = 0.699; P <.0001). The ultrasound-measured size and volume differed from the pathology-reported size and volume (P <.0001; Wilcoxon signed ranks test). Concordance between the clinical tumor size stage from ultrasound (cT) and pathology tumor size stage (pT) varied with the pT stage (P =.0003, Fisher's exact test), with the greatest concordance rate of 95.7% (95% confidence limit, 85.2%-99.5%) observed for pT1 tumors. Conclusion: Ultrasonography underestimates the tumor size and volume, with the underestimation increasing for larger tumors. Hence, the concordance rate in tumor size stage between ultrasonography and pathology is tumor size dependent, with the greatest concordance rate observed for pT1 tumors.