Extramammary Paget disease (EMPD) is a diagnostic challenge. In vivo reflectance confocal microscopy (RCM) has been reported to be useful for in vivo skin tumor evaluation. It may also assist in the surgical management of EMPD lesions.

We sought to describe confocal features of EMPD and correlate them with histopathologic findings. The potential of RCM to map the lesions for subsequent surgical management was also investigated.

A total of 23 lesions from 14 recruited patients were evaluated by RCM and histopathologic examination. RCM was used to delineate preoperative surgical margins in two patients.

Erythematous, hyperpigmented, and hypopigmented lesions were evaluated by RCM and results were confirmed by histopathologic examination. Paget cells were observed throughout the epidermis. Typical Paget cells on RCM were characterized by a mild bright nucleus and dark cytoplasm, frequently twice the size of keratinocytes or larger. At the dermoepidermal junction, tumor nests were seen as dark glandular structures. A high density of dendritic cells was observed in pigmented lesions and a low density in erythematous lesions. Dilated vessels and inflammatory cells were seen in pigmented and erythematous lesions. Paget cells within the epidermis and nest structures at the dermoepidermal junction were seen in most lesions. These two features were useful for delineating the margins. Histologic examination corroborated the surgical margins found by RCM.

The sensitivity and specificity of these diagnostic features have not been fully studied, and differential diagnostic features require exploration.

Features correlating well to histopathology are observed on the RCM of EMPD lesions. RCM may be used as an auxiliary diagnostic tool for the diagnosis and management of EMPD.