A soft tissue swelling is a common clinical presentation, and although the majority of causes are benign, an intermediate or malignant diagnoses must be ruled out. A thorough history and examination are key to highlight any red flags such as rapid growth, a large tumour size (>5 cm), a deep location, pain or recurrence. These flags should be investigated thoroughly, and if there is any diagnostic uncertainty patients should be discussed with a sarcoma multidisciplinary team (MDT) prior to treatment, and biopsy considered. The inadvertent resection of a malignant soft tissue sarcoma (termed a ‘whoops’ procedure) must be avoided at all costs. Ultrasound is a cheap and easily accessible first-line imaging modality that in specialist hands can identify or rule out aggressive features accurately. Magnetic resonance imaging is the gold standard cross-sectional imaging modality for soft tissue tumours, and allows a detailed anatomical assessment key for surgical planning. Most benign lesions can be managed conservatively or with active surveillance, although symptomatic patients may benefit from a surgical excision. Intermediate tumours should be managed in conjunction with a sarcoma MDT given their rarity and complexity, and will usually require an excision.