Abstract
A chronic expanding hematoma （CEH） is a hematoma with long-term, continuous growth which is often clinically mistaken for soft-tissue neoplasm. In the majority of cases, hematomas appear acutely and resolve spontaneously, but sometimes, they become encapsulated by a fibrous wall, leading to chronic swelling that slowly expands and increases progressively with time. A 31-year-old female presented with a knee CEH five years after trauma. The differential diagnosis between a CEH and soft-tissue neoplasm could not be confirmed, even after imaging findings and a biopsy were completed. The tumor was completely excised and histologically diagnosed as a CEH. CEH should be considered when making differential diagnoses of soft-tissue neoplasms.
