45 year old female presented with a left breast lump for 3 months.
On ultrasound, there is a small, well defined, anechoic lesion with posterior enhancement, noted located close to the skin surface with through transmission at 7 o'clock, subareolar region. It measures 6mm in diameter. On color Doppler, there is no internal vascularity. Ultrasound findings are suggestive of sebaceous cyst.

Breast sebaceous cyst, also sometimes known as an epidermal inclusion cyst or simply epidermoid cyst, is a benign breast lesion (BIRADS II). 
The two terms, breast sebaceous cyst and epidermal inclusion cyst, are not entirely synonymous as a sebaceous cyst has an epithelial lining as opposed to an epidermal inclusion cyst, which has an epidermal lining. As far as imaging is concerned, the two entities are indistinguishable from each other and the terms are used interchangeably.
These lesions are typically located in the skin or subcutaneous tissue. There may be a predilection towards the inframammary fold.

Acknowledgement: Dr Ashikin Bt Mohamed Adib (Klinik Aman)