I saw the sign: Go nuts, it's the “acorn cyst” sign

Abstract

The “acorn cyst” sign is an imaging sign encountered on breast ultrasound exams denoting a type of benign complicated cyst. An acorn cyst is comprised of a deep anechoic fluid portion (the “acorn”) and a more superficial echogenic layer of material (the “acorn cap”). Radiologists should attempt to distinguish the acorn cyst from more suspicious complex cystic and solid masses; if unable to do so, aspiration/biopsy can be performed to exclude a malignant lesion.