-Review the ultrasound features that allow typing a lesion as a complex cystic and solid mass. -Analyse the different histological results derived from the anatomopathological study of these lesions through cases presented in our hospital, which includes a wide spectrum of benign, atypical and malignant pathologies.

Cysts are by far the most frequently encountered breast condition and are usually asymptomatic and found accidentally while performing an ultrasound examination. Among the changes found in the 5th edition of the BIRADS system of the American College of Radiology (ACR) is the substitution of the term "complex cyst" for "complex cystic and solid mass” in order to reduce confusion with the complicated cyst.

Ultrasound is the technique of choice in the evaluation of cystic lesions of the breast. In addition, it is a very useful tool as a biopsy guided, providing greater performance in obtaining samples. There are three types of breast cysts: - Simple cysts: Strictly anechoic content with a thin imperceptible wall and posterior acoustic enhancement. By convention, simple cysts may also contain up to a single thin septation. Simple cysts are confidently characterized with virtually 100% accuracy at US. As benign lesions (BI-RADS 2 category),...

1. It is essential to differentiate between a complicated or complex cystic lesion: its proper classification will allow us to quantify the risk of malignancy and will condition the attitude in the management and follow-up. 2. Patient´s mobilization and the use of color Doppler are very useful tools in distinguishing the solid nature of complex cysts from the echogenic content of complicated cysts. 3. Complex cysts and solid masses include a wide spectrum of both benign and malignant pathologies, requiring percutaneous biopsy and/or surgical ablation...

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