Value of pseudopod sign on high‐frequency ultrasound in predicting the pathological invasion of extramammary Paget's disease lesions
Dan-Dan Shan, Nanhui Wu, Q. Wang, Weiwei Ren, Aibin Zhu, Lei Wang, Ying Liu, Liping Sun, Le‐Hang Guo, Hui‐Xiong Xu
Abstract
BACKGROUND: Vertical invasion of extramammary Paget's disease (EMPD) is associated with poor prognosis. The usual vertical invasion route is directly downward or along the skin appendages. High-frequency ultrasound (HFUS) can be used to measure the EMPD lesion thickness, and visualize the pseudopod extensions due to skin appendage involvement. It is a non-invasive method for evaluating the extent of vertical invasion in EMPD. OBJECTIVE: To investigate the value of HFUS in predicting the extent of vertical invasion in EMPD. METHODS: In this retrospective study, 85 patients with EMPD were divided into two groups based on the pathology: invasive EMPD (iEMPD) group (n = 13) and in situ EMPD group (n = 72). The clinical and HFUS features of both the groups were analysed. The different types of pseudopodia morphology on HFUS were as follows: no pseudopodia, irregular bottom, small sphere, short strip, long strip, vase shape and nodular convex. These were further stratified into low-risk and high-risk levels. RESULTS: The clinical features were comparable between the two groups (P > 0.05). There were significant differences between the two groups in the HFUS features (lesion thickness, lesion shape, bottom shape, layer involvement, pseudopodia morphology and colour Doppler blood flow signal; all P < 0.05). The distribution of the pseudopodia morphology types in the in situ EMPD and iEMPD groups was as follows: no pseudopodia, 30/72 and 0/13; irregular bottom, 5/72 and 0/13; small sphere, 5/72 and 0/13; short strip, 21/72 and 0/13; long strip, 8/72 and 3/13; vase shape, 3/72 and 3/13; and nodular convex, 0/72 and 7/13 (P < 0.05 for all). The sensitivity and specificity of high-risk pseudopodia in identifying iEMPD were 100% and 84.7%, respectively. CONCLUSIONS: High-frequency ultrasound provides morphological information regarding EMPD lesions. Risk stratification for pseudopodia can help to distinguish between iEMPD and in situ EMPD lesions.