Abstract
Pyomyositis in immunocompromised patients may present only minimal inflammatory changes and thus clinically mimic soft tissue tumour. We report two patients with pyomyositis which was initially suspected to be a soft tissue tumour. Patient 1 was a 64–year–old woman who had pyomyositis at the distal part of the left thigh. She had uncontrolled diabetes mellitus. Causative organism was gram positive rods. Patient 2 was a 54–year–old man who had pyomyositis at the medial head of the gastrocnemius. He had ill–controlled diabetes mellitus. Causative organism was Staphylococcus aureus. Both of them were immunocompromised hosts. They showed minimal inflammatory findings and the swelling of the muscles took the appearance of a soft tissue tumour rather than pyomyositis. The inflammation prevailed beyond the muscle compartment and fluid collection representing abscess were seen on MR images. Patient 1 was treated conservatively and Patient 2 was treated surgically. When needle biopsy is performed for soft tissue tumour–like lesions even with minimal inflammatory changes, not only histological examination but also bacteriological examination should be performed.
