title: Skeletal Muscle Metastasis from Renal Cell Carcinoma: 21 cases and review of the literature.
abstract: OBJECTIVE
  This study aimed to raise radiologists' awareness of skeletal muscle metastases (SMM) in renal cell carcinoma (RCC) cases and to clarify their imaging appearance.
  
  
  METHODS
  A retrospective analysis was undertaken of 21 patients between 44-75 years old with 72 SMM treated from January 1990 to May 2009 at the MD Anderson Cancer Center in Houston, Texas, USA. Additionally, 37 patients with 44 SMM from a literature review were analysed.
  
  
  RESULTS
  Among the 21 patients, the majority of SMM were asymptomatic and detected via computed tomography (CT). Mean metastasis size was 18.3 mm and the most common site was the trunk muscles (83.3%). The interval between discovery of the primary tumour and metastasis detection ranged up to 234 months. Peripheral enhancement (47.1%) was the most common post-contrast CT pattern and non-contrasted CT lesions were often isodense. Magnetic resonance imaging (MRI) characteristics were varied. Five lesions with available T1-weighted pre-contrast images were hyperintense to the surrounding muscle. Other organ metastases were present in 20 patients. Of the 44 SMM reported in the literature, the majority were symptomatic. Average metastasis size was 53.4 mm and only 20.5% of SMM were in trunk muscles. The average interval between tumour discovery and metastasis detection was 101 months. Other organ metastases were recorded in 17 out of 29 patients.
  
  
  CONCLUSIONS
  SMM should always be considered in patients with RCC, even well after primary treatment. SMM from RCC may be invisible on CT without intravenous contrast; contrast-enhanced studies are therefore recommended. SMM are often hyperintense to the surrounding muscle on T1-weighted MRI scans.
authors.affiliation: Department of Diagnostic Radiology, MD Anderson Cancer Center, Houston, Texas, USA;
authors.forename: Tamara Miner
authors.initials: TM
authors.lastname: Haygood
authors.affiliation: Department of Diagnostic Radiology, University of Michigan Health System, University of Michigan, Ann Arbor, USA;
authors.forename: Mohamed
authors.initials: M
authors.lastname: Sayyouh
authors.affiliation: British Columbia Centre for Disease Control, Vancouver, British Columbia, Canada; ; School of Population & Public Health, University of British Columbia, Vancouver, British Columbia, Canada;
authors.forename: Jason
authors.initials: J
authors.lastname: Wong
authors.affiliation: Radiology Medical Group, Santa Cruz, California, USA.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Lin
authors.affiliation: Department of Diagnostic Radiology, MD Anderson Cancer Center, Houston, Texas, USA;
authors.forename: Aurelio
authors.initials: A
authors.lastname: Matamoros
authors.affiliation: Department of Diagnostic Radiology, MD Anderson Cancer Center, Houston, Texas, USA;
authors.forename: Carl
authors.initials: C
authors.lastname: Sandler
authors.affiliation: Department of Diagnostic Radiology, MD Anderson Cancer Center, Houston, Texas, USA;
authors.forename: John E
authors.initials: JE
authors.lastname: Madewell
keywords: Metastasis; Renal Cell Carcinoma; Skeletal Muscle; United States