Preliminary Evaluation of Pocket Oral Echo, a Novel Compact Intraoral Ultrasound System, for Assessing Depth of Invasion in Tongue Squamous Cell Carcinoma: An Ex Vivo Histopathological Correlation Study

Aims This study aimed to preliminarily evaluate the feasibility of pocket oral echo (POE), a newly developed compact intraoral ultrasound system, for visualizing superficial tumor invasion and assessing depth of invasion (DOI) in surgically resected specimens of early tongue squamous cell carcinoma (SCC) with comparison to histopathological findings. Methods Three surgically resected specimens of T1N0 tongue SCC were examined within 10 min after resection using a precommercial version of POE equipped with a toothbrush‐shaped 10‐MHz linear transducer. The US‐derived DOI (US‐DOI) was measured perpendicularly from a reconstructed line corresponding to the epithelial–submucosal interface of the adjacent normal mucosa to the deepest point of the hypoechoic tumor region. Ultrasonographic findings were compared with corresponding histopathological sections. Results POE visualized all three tongue SCCs as hypoechoic abnormalities continuous with the mucosal epithelial layer. The deepest tumor margin was identifiable in all specimens. The US‐DOI measurements were 1.0, 0.7, and 3.0 mm, compared with histopathological DOI values of 0.5, 1.0, and 2.0 mm, respectively. Ultrasonographic tumor morphology showed close correspondence with the histopathological findings. Conclusions The precommercial POE system enabled visualization and measurement of very superficial invasion in resected specimens of early tongue SCC, including lesions with histopathological DOI values of less than 1 mm. These preliminary ex vivo findings support the technical feasibility of POE for DOI assessment and warrant prospective in vivo evaluation in a larger cohort. Trial Registration: Not applicable.