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Pathology & Laboratory Medicine

URMC / Pathology & Laboratory Medicine / Education / Case of the Month / Case 55: Hip Mass / Diagnosis

 

Diagnosis & Discussion

Diagnosis

Intramuscular angioma.

Discussion

Intramuscular angioma (IA) is a proliferation of benign vessels within skeletal muscle, nearly universally associated with a component of mature adipose tissue. IA is thought to be a vascular malformation rather than a bona fide vascular neoplasm. IA has a predilection for the lower limbs, especially the thigh. Other sites of involvement, in order of decreasing frequency, include the head and neck region, the upper limbs, and the trunk. IAs commonly present as a mass lesion or with chronic pain (pain is present in 60% of cases).

Radiographically, magnetic resonance imaging is the imaging modality of choice and may enable distinction from malignant soft tissue tumors sparing the patient a biopsy. Phleboliths are present in 25% of cases and are a helpful imaging clue to the diagnosis of IA when present.

Most IAs are first managed conservatively with clinical follow-up at regular intervals. If conservative management fails, surgical management is considered for IAs with intractable pain, rapid tumor growth, clinical concern for malignancy, risk of skin necrosis, thrombocytopenia, functional impairment, or cosmetic deformity.

Although IA is benign there is a high local recurrence rate (up to 60% of cases). The high recurrence rate is thought to be primarily due to the large size of these tumors and their ill-defined and infiltrative margins.

Histologically, IA is composed of a proliferation of benign vessels infiltrating skeletal muscle. There is virtually always a component of mature adipose tissue within the lesion that can be highly variable in extent. Given this adipocytic component, IA was previously known as “infiltrating angiolipoma.”

The main entity on the histologic differential diagnosis is intramuscular lipoma since both entities contain mature adipose tissue; however, the vascular component of IA is far more prominent than that seen in intramuscular lipoma. The differentiation of these two entities is clinically relevant since the recurrence rate for intramuscular lipoma (approximately 20%) is far less than that of IA.

References

1. Calonje JE. Hemangiomas. In Fletcher CDM, Bridge JA, Hogendoorn P, Mertens F. (2013). WHO Classification of Tumours of Soft Tissue and Bone. Fourth Edition. Lyon, France: IARC.

2. Gleason BC, Hornick JL. Vascular Tumors. In Hornick, JL. (2013). Practical soft tissue pathology: A diagnostic approach. Second Edition. Philadelphia, PA: Elsevier/Saunders.

3. Wierzbicki JM, Henderson JH, Scarborough MT, Bush CH, Reith JD, Clugston JR. Intramuscular hemangiomas. Sports Health. 2013;5:448–454.

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