AKT · Endocrine/Breastlow yield

Fat necrosis

Benign inflammatory response to breast fat injury (trauma/surgery)

Overview

A benign inflammatory reaction to injury of breast fat (trauma, surgery, radiotherapy, often in larger breasts). It produces a firm, sometimes irregular and skin-tethered lump that can clinically and radiologically MIMIC cancer — so it is diagnosed by triple assessment, not assumed from a trauma history.

Recognise

Firm, sometimes irregular lump ± skin tethering/bruising, often after trauma or breast surgery
Can mimic carcinoma clinically and on mammography (may have calcification/spiculation)
Often resolves over weeks–months

Red flags

Any solid lump must complete triple assessment — do not attribute to trauma without excluding cancer

Differentials & how to tell them apart

Breast cancerthe key mimic — imaging/biopsy distinguishes; don't rely on a trauma history alone

Haematomarecent trauma, resolves; ultrasound

Investigations

Triple assessment with imaging and core biopsy to confirm (oil cysts/fat necrosis) and exclude malignancy.

Management

Triple assessment to confirm benign; then reassurance

1Complete triple assessment to confirm fat necrosis and EXCLUDE malignancy. Reassure once benign.Gate: A trauma history does NOT excuse a lump from triple assessment — fat necrosis mimics cancer clinically and radiologically; biopsy is what makes it safe to reassure
2Observation; most resolve. Excision only if symptomatic or diagnostic doubt persists.

Reassurance/observation — after benign triple assessment

Key points

Firm tethered lump after trauma/surgery = could be fat necrosis, but it mimics cancer — triple-assess before reassuring.

Monitor & prognosis

Resolution; re-image if not.

Benign; resolves.

Source: NICE NG101