Intermuscular and intramuscular lipomas and hibernomas.A clinical, roentgenologic, histologic, and prognostic study of 46 cases

A series of 9 intermuscular and 34 intramuscular lipomas, and 1 intermuscular and 2 intramuscular hibernomas is presented. One intramuscular lipoma infiltrated not only muscle but also fascia and tendon. The shoulder region and the thigh were the most common sites of the lipomas. Clinically the tumor appeared in most cases as a painless, fairly soft mass. Dysfunction of the engaged muscle was apparent in only 4 patients. A characteristic change in consistency and form was shown in 14 cases: the tumor being soft and flat when the muscle was relaxed, and becoming firm and more spherical when the muscle was contracted. Some tumors, having developed in a closed fascial space, were firm on palpation even when the muscle involved was relaxed. Radiography was performed in 36 patients with lipoma. In 31 of these the tumor was clearly visible because of its radiotranslucency. Streaks of higher density caused by muscle fiber bundles were seen within the tumor area in some cases. Angiography was performed in 14 patients with lipoma. Usually the tumor appeared poor in vessels in relation to surrounding muscle, and in no patient was increased vascularity, abnormal vessel formation, or early venous filling observed. Microangiography of 2 of the lipomas demonstrated their poor vascular supply in relation to the surrounding muscle. Angiography in 2 patients with hibernoma showed that the tumor was highly vascular with irregular vessels and early venous filling, findings usually held as contributory signs of malignancy in the diagnosis of soft tissue tumors. Microangiographic studies of these hibernomas, earlier reported, also demonstrated their high vascularity. A followup study has shown the benign course of intermuscular and intramuscular lipoma and hibernoma.