Breast for FRCS (Gen Surg)

This is a simple breast cyst, an aberration of normal involution that peaks in the decade before the menopause. When imaging shows a simple cyst, the aspirate is not bloodstained and the lump resolves completely, no further action is needed: cytology of ordinary cyst fluid has a negligible yield of cancer and generates false-positive atypia, so the fluid is discarded. Cytology or biopsy is indicated when the fluid is uniformly bloodstained, a mass persists after aspiration or imaging shows an intracystic or solid component. Scheduled repeat ultrasound is unnecessary, as she can return if a lump recurs, and many cysts refill harmlessly. Excision of a simple cyst is not indicated. Reference: Dixon JM (ed.), Breast Surgery: A Companion to Specialist Surgical Practice, 6th edn; Willett AM et al., Best practice diagnostic guidelines (2010).

This is invasive lobular carcinoma, which infiltrates as single files of discohesive cells with little stromal reaction, so mammography and ultrasound commonly underestimate its size and miss multifocal or contralateral disease. NICE recommends MRI of the breast for invasive lobular cancer when breast-conserving surgery is being considered, and when clinical and imaging size disagree, as here; it lowers the risk of involved margins and re-operation. CT and PET-CT stage distant disease and are not indicated in a clinically early, node-negative cancer. Tomosynthesis adds little to the assessment of extent in lobular disease. The diagnosis is already secure, so a larger-volume biopsy would not change the plan. Reference: NICE NG101, Early and locally advanced breast cancer (2018, updated 2025); Dixon JM (ed.), Breast Surgery: A Companion to Specialist Surgical Practice, 6th edn.