From Ultrasound to Histopathology: Agreement Analysis and Depth Correction Model for Basal Cell Carcinoma Using a Portable 20 MHz High-Frequency Ultrasound Device

Background: High-frequency ultrasound (HFUS) represents a valuable non-invasive imaging modality for assessing cutaneous tumors. In basal cell carcinoma (BCC), preoperative estimation of tumor depth may support therapeutic decision-making and surgical planning. However, agreement between HFUS-derived and histopathologic depth measurements remains incompletely characterized, particularly with 20 MHz probes in routine clinical practice. Objectives: To evaluate agreement between 20 MHz HFUS and histopathology for BCC tumor depth using Bland–Altman analysis and to derive a preliminary correction equation to estimate histologic depth from HFUS measurements. Methods: This prospective observational pilot study included 15 patients with 16 histologically confirmed BCC lesions. All lesions underwent preoperative 20 MHz HFUS followed by surgical excision, with HFUS-derived tumor depth compared with histopathologic depth. Agreement was assessed using Bland–Altman analysis, and linear regression was performed to derive a preliminary correction equation. Results: Sixteen BCC lesions were analyzed. The mean difference between HFUS and histopathologic tumor depth was −0.07 mm, with 95% limits of agreement from −1.58 to +1.45 mm. HFUS and histopathologic depth measurements were highly correlated (R2 = 0.99). A correction equation was derived: estimated histopathologic depth (mm) = −0.52 + 1.10 × HFUS depth (mm). Conclusions: Twenty MHz HFUS demonstrated good agreement with histopathology for tumor depth assessment in BCC, with clinically acceptable variability. The proposed correction equation may improve interpretation of HFUS measurements; however, further validation in larger cohorts is required.