Chronic Expanding Hematoma

The term chronic expanding hematoma refers to hematomas that increase in size for over a month after initial hemorrhage. Similar lesions in the bones and soft tissues in patients with hemophilia are called hemophilic pseudotumors.

The persistence and growth of these lesions is thought to be due to the irritative properties of blood and its breakdown products, causing repeated capillary injury and episodic bleeding into the main cavity.

It is unclear why most hematomas spontaneously resolve, while some persist and develop vascular ingrowth, and others calcify peripherally.

Chronic expanding hematomas have been reported in the soft tissues of the extremities, body wall musculature, and visceral organs.

Radiographs reveal a soft tissue mass with or without calcifications and adjacent bone destruction or pressure erosion. CT shows a heterogeneous or homogeneous low-attenuation mass that can have peripheral or internal calcifications and adjacent bone destruction or pressure erosion.

On MRI, chronic expanding hematomas have a pseudocapsule that is low signal intensity of T1- and T2-weighted sequences and is composed of fibrous tissue, hemosiderin deposits and iron-laden macrophages. The pseudocapsule can enhance.

Centrally, they have areas of heterogeneous signal intensity on both T1-weighted and T2-weighted sequences that correspond to a mixture of blood breakdown products; loose connective tissue; granulation tissue with capillary ingrowth; inflammatory tissue; and cavitary collections of necrotic debris, fibrin and blood clots.

Contrast enhancement within benign hematomas is rare, but has been reported. It implies the presence of viable tissue, an intact vascular supply, and abnormal capillary permeability within the central portion of the hematoma.

The most important differential consideration is a hemorrhagic soft tissue sarcoma, which can have a similar appearance on non-contrast MRI. The presence of gadolinium enhancement helps point toward neoplasm.

References

• Aoki T, Nakata H, Watanabe H, Maeda H, Toyonaga T, Hashimoto H, Nakamura T. The radiological findings in chronic expanding hematoma. Skeletal Radiol. 1999 Jul;28(7):396-401.
• Batista GR, Rocha Oliveira PC, Alcantara FP, de Teles IG, Senna Najjar YJ, Kalil RK. Chronic diploic hematoma mimicking malignancy on imaging. Skeletal Radiol. 2011 Apr;40(4):475-9.
• Reid JD, Kommareddi S, Lankerani M, Park MC. Chronic expanding hematomas. A clinicopathologic entity. JAMA. 1980 Nov 28;244(21):2441-2.