title: Injection site pseudosarcoma in piriformis syndrome.
abstract: OBJECTIVE
  Pseudosarcomatous reactive myofibroblastic proliferations have been described following surgery or trauma at a variety of anatomical sites. These types of reactions have not been previously described at injection sites. Here we evaluated prevalence, morphologic patterns and clinical resolution of such lesions.
  
  
  RESULTS
  We analyzed 266 surgical resection specimens obtained during the definitive treatment of piriformis syndrome. Three cases showed exuberant reactive fibroblastic/myofibroblastic intramuscular proliferations, mimicking a sarcoma. In all three cases the surgeries were found to be preceded by local injections of cortisone and bupivacaine. Clinical follow-up revealed no uncontrolled growth.
  
  
  CONCLUSIONS
  As the clinical history of injections is often not provided, it is important to be aware of this pitfall when reviewing skeletal muscle resections for entrapment syndromes.
authors: Department of Pathology and Laboratory Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.
authors: Dan C
authors: DC
authors: Phan
authors: Briana C
authors: BC
authors: Gleason
authors: Xuemo
authors: X
authors: Fan
authors: Owen T M
authors: OT
authors: Chan
authors: Eric
authors: E
authors: Himmelfarb
authors: Serguei I
authors: SI
authors: Bannykh
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007273:Injections, Intramuscular / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000293:injuries / Q000473:pathology*; D009220:Myositis / Q000209:etiology / Q000473:pathology*; D055958:Piriformis Muscle Syndrome / Q000209:etiology / Q000473:pathology*; D012509:Sarcoma / Q000175:diagnosis*