title: [The differential diagnosis of malignant soft tissue tumors: pyomyositis].
abstract: The case of a seven-year-old boy with an enlarging woody-hard mass in the upper thigh is described and the related literature is reviewed. In absence of conclusive signs of inflammation on both clinical and radiological findings a malignant soft tissue tumour was initially suspected. On operation the mass was found to contain multiple loculated abscesses, and turned out to be a subacute staphylococcal myositis (pyomyositis). Such lesions are quite common in subtropical and tropical climates, and a review of the literature indicates that the incidence of this formerly rare entity is increasing in temperate climates. A variety of factors play a role in pathogenesis, and a history of previous aseptic trauma can be found in about 50% of all cases. The most frequent location is the proximal lower limb or buttock. The clinical history and physical findings are often non-specific. Plain radiographs are non-diagnostic; ultrasound, CT and/or MRI may in some cases be equivocal and angiography sometimes is even misleading. It is important to keep this differential diagnosis in mind, especially in children.
authors.affiliation: Institut für Radiologische Diagnostik, Universität Köln.
authors.forename: P
authors.initials: P
authors.lastname: Ahrens
authors.forename: W
authors.initials: W
authors.lastname: Gross-Fengels
authors.forename: K
authors.initials: K
authors.lastname: Bovelet
mesh_terms: D015901:Angiography, Digital Subtraction; D002648:Child; D003937:Diagnosis, Differential; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009220:Myositis / Q000175:diagnosis* / Q000000981:diagnostic imaging; D012983:Soft Tissue Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000000981:diagnostic imaging; D013848:Thigh; D014463:Ultrasonography