2. Case presentation
The patient, a 31-year-old male, was found several hemispheric nodules in the skin or subcutaneous of both buttocks, disease course of 5 years, and these nodules were slightly soft. The patient did not feel painful and itching in his buttocks, and the skin of buttocks was intact. The masses of bilateral buttocks had significantly increased in the past 1 month. The case underwent mass resection and pathological examination, and recovered well with no relapse within 5 years after surgery.
Physical examination : By palpation, we found all masses with poor mobility, moderate texture and no fluctuation.
Laboratory examination : Through laboratory tests, we found that serum triglyceride was 1.62 mmol/L (normal value 0.29-1.83mmol/L), low-density lipoprotein was 11.2 mmol/L (normal value < 4.0mmol/L), high-density lipoprotein was 1.51 mmol/L (normal value > 0.9 mmol/L), and cholesterol was 16.7 mmol/L (normal value 2.8-5.7 mmol/L).
Ultrasonic findings : We found that multiple hyper echoic masses were in the skin layer of bilateral buttocks, and the biggest mass of left buttock was about 69×14×44 millimeter in size, with clear boundary and irregular morphology (Fig. 1). Abundant blood flow signals were seen within the masses, and low-velocity, low-obstruction artery and low-velocity venous blood flow spectrum were detected (Fig. 2).
Postoperative pathological specimens : Two masses were about 31×15×30 millimeter and 30×25×30 millimeter in size on right buttock respectively, and a lump was about 69×14×44 millimeter in size on left buttock. The sizes of above masses were all consistent with that measured by ultrasound.
Pathological findings : Histopathologic lesions of masses on left and right buttocks were analyzed by immunohistochemical and histochemical staining. The masses were mainly composed of a large number of focal-like foam cells, which were nodular in distribution(Fig. 3A). Inflammatory cell infiltration, fibroblast hyperplasia with a small amount of cholesterol deposition and hyaline degeneration were seen in some areas(Fig. 3A). Immunohistochemic: S-100 (-), Leu-7 (-), Desmin (-), SMA (-), inhibin (-), CD68 (+), which supported the pathological diagnosis with xanthomas (Fig. 3B).