title: Alveolar rhabdomyosarcoma confined to the bone marrow with no identifiable primary tumour using FDG-PET/CT.
abstract: BACKGROUND
  Rhabdomyosarcoma (RMS), a malignant tumour of mesenchymal origin which can occur at various sites in the body, is one of the most common soft tissue sarcomas in both children and adolescents, but is rare in adults with a prevalence of less than 1 %. The alveolar subtype of rhabdomyosarcoma (ARMS) is typically characterized by a specific reciprocal chromosomal translocation involving the PAX3 and FKHR or PAX7 and FKHR genes, respectively. ARMS is most frequently seen in childhood, and typically affects the sinuses and soft tissue of the extremities, with approximately 23 % exhibiting metastasis to the marrow. Non-invasive F-18-fluorodeoxyglucose positron-emission tomography (FDG-PET) scans have a high ability to detect lymph nodes, bone, and bone marrow involvement in patients with metastatic RMS, often with higher sensitivity and specificity compared with conventional modalities.
  
  
  METHODS
  Here, we report an unusual case of ARMS confined to the bone marrow in an older adult that lacked an identifiable primary tumour using FDG-PET/CT and mimicked a haematological disease with pancytopenia but without abnormal findings by FDG-PET/CT. The patient was initially treated with topotecan/cyclophosphamide and subsequently switched to vinorelbine. Due to severe toxicity the treatment was discontinued, however after 7-months follow-up, the patient is still alive with an improved general state of health and only a mild pancytopenia with no need for blood transfusions.
  
  
  CONCLUSIONS
  Rhabdomyosarcoma can be limited to the bone marrow with no identifiable primary tumour. This case shows that the use of a bone marrow biopsy in suspected malignancies affecting the bone marrow is irreplaceable.
authors.affiliation: Department of Oncology, Haematology and Stem Cell transplantation, University Hospital of Hamburg Eppendorf, Hamburg, Germany.|NIHR Biomedical Research Centre at Guy's and St. Thomas's Hospitals and King's College London, London, United Kingdom.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Karagiannis
authors.affiliation: Department of Oncology, Haematology and Stem Cell transplantation, University Hospital of Hamburg Eppendorf, Hamburg, Germany.
authors.forename: Nina
authors.initials: N
authors.lastname: Guth
authors.affiliation: Department of Oncology, Haematology and Stem Cell transplantation, University Hospital of Hamburg Eppendorf, Hamburg, Germany.
authors.forename: Gabriela B
authors.initials: GB
authors.lastname: Thoennissen
authors.affiliation: Department of Radiology and Nuclear Medicine, University Hospital of Hamburg Eppendorf, Hamburg, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Bern
authors.affiliation: Gerhard-Domagk-Institute of Pathology, University Hospital of Muenster, Muenster, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Sperveslage
authors.affiliation: Institute of Pathology, University Hospital of Schleswig- Holstein, Kiel, Germany.
authors.forename: Ilske
authors.initials: I
authors.lastname: Oschlies
authors.affiliation: Department of Oncology, Haematology and Stem Cell transplantation, University Hospital of Hamburg Eppendorf, Hamburg, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Bokemeyer
authors.affiliation: Institute of Pathology, University Hospital of Schleswig- Holstein, Kiel, Germany.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Klapper
authors.affiliation: Gerhard-Domagk-Institute of Pathology, University Hospital of Muenster, Muenster, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Wardelmann
authors.affiliation: Department of Oncology, Haematology and Stem Cell transplantation, University Hospital of Hamburg Eppendorf, Hamburg, Germany.
authors.forename: Nils H
authors.initials: NH
authors.lastname: Thoennissen
keywords: Alveolar rhabdomyosarcoma; Bone marrow; FDG-PET; Rhabdomyosarcoma; Topotecan/cyclophosphamide; Vinorelbine