Ultrasonography is a method of imaging that classically is used in dermatology to study changes in the hypoderma, as nodules and infectious and inflammatory processes. The introduction of high frequency and resolution equipments enabled the observation of superficial structures, allowing differentiation between skin layers and providing details for the analysis of the skin and its appendages. This paper aims to review the basic principles of high frequency ultrasound and its applications in different areas of dermatology.

The present essay is aimed at getting the radiologist familiar with the basic histological skin structure, allowing for a better correlation with sonographic findings. A high-frequency (22 MHz) ultrasonography apparatus was utilized in the present study. The histological analysis was performed after the skin specimens fixation with formalin, inclusion in paraffin blocks and subsequent staining with hematoxylin-eosin. The authors present a literature review showing the relationship between sonographic and histological findings in normal cutaneous tissue, and discuss the technique for a better performance of the sonographic scan. High-frequency ultrasonography is an excellent tool for the diagnosis of different skin conditions. However, as this method is operator-dependent, it is crucial to understand the normal skin structure as well as the correlation between histological and sonographic findings.

The recent development of high-frequency ultrasound, associated with the improved sensitivity in color Doppler, enabled the identification of various skin structures and layers. In basal cell carcinoma, the 22 MHz frequency ultrasound permits the delimitation of tumor margins, while color Doppler, determines its vascularization. We present two cases in which the association of both exams allowed an in vivo analysis of the tumor's morphology, size, thickness and vascularization, thus contributing to a better pre-operative evaluation.

The worldwide incidence of basal cell carcinoma (BCC) has increased significantly in recent decades. [1][2][3] BCC is an epithelial malignancy that accounts for 75%-80% of all skin tumors in fair-skinned adults.It usually affects sun-exposed areas of the skin; the face is the most prevalent site of involvement. 4 Although BCCs grow slowly, they may be locally invasive and destructive.The main goal of primary BCC treatment is to completely eradicate the tumor with maximal preservation of function and cosmesis. 5 Treatment can be medical or surgical. Because of the likelihood of local recurrence, 6,7 surgical treatment is recommended. 5 However, overestimation of tumor size can lead to poor cosmetic outcomes. Conversely, incomplete excision can induce changes in tumor structure, leading to more aggressive tumor behavior. 7,8 In cases that are treated non-surgically, therapeutic success also depends on proper assessment of lesion depth. Thus, determinating the extent of tumor depth may help clinicians to select the optimal approach to treatment and the likelihood of achieving a negative resection margin. 6

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