<s>[INST] I was in a fatal car crash 2 weeks ago, my seatbelt left a large bruise almost completely covering my right breast. I wear a d cup and sometimes a dd so that s nothing small. The bruise is almost completely gone but there s now a lump- not a huge one but a lump I did not recognize prior to the accident. Could this be a hematoma? Should I be alarmed? [/INST] Hello and welcome to Chat Doctor, A breast lump formed after trauma is most probably due to organized hematoma. Traumatic fat necrosis is also one of the possibility. However, the history does not point towards any malignancy. A clinical assessment and imaging study of the lesion is required. Imaging will determine the site and probable nature of the lesion. An aspiration cytology will also help. In aspiration cytology, a needle is inserted into the lesion, cells are aspirated, spread on a slide and stained with appropriate stains and examined under microscope. On studying the cells, the probable nature of lesion is known and thus management can be planned. Thanks and take care Chat Doctor.  </s>