title: Anaplastic lymphoma kinase-negative anaplastic large cell lymphoma with extranodal involvement of the thigh muscle: a case report.
abstract: BACKGROUND
  Anaplastic large cell lymphoma is a rare type of non-Hodgkin lymphoma. The most common extranodal sites of anaplastic large cell lymphoma are skin, subcutaneous tissue, bone, lung, and gastrointestinal organs. The involvement of the skeletal muscle has been described rarely in extranodal anaplastic large cell lymphoma.
  
  
  METHODS
  An 89-year-old Japanese man visited our hospital with a three-month history of swelling of his left thigh and slight fever. The swelling had rapidly enlarged and become painful within the previous three days. Magnetic resonance imaging scans revealed two soft-tissue tumors in the intramuscular layer between the vastus medialis muscle and the adductor muscle. Extensive peritumoral inflammatory edema was obvious. As the results of physical and radiological examinations were highly suggestive of abscess formation, we prescribed antibiotics for two weeks. However, our patient's symptoms did not improve. Therefore, we suspected a soft-tissue sarcoma, and our patient underwent an incision biopsy. Histological analysis revealed that the atypical cells were positive for CD3 and CD30 but negative for anaplastic lymphoma kinase. A computed tomography scan of the thorax revealed mediastinal lymphadenopathy and bilateral pleural effusions, suggestive of extranodal involvement of skeletal muscle in anaplastic lymphoma kinase-negative anaplastic large cell lymphoma. We planned to give our patient systemic chemotherapy. However, rapid systemic dissemination occurred and our patient died of multiple organ failure five weeks after his first visit to our hospital.
  
  
  CONCLUSIONS
  Here, we present a case of anaplastic lymphoma kinase-negative anaplastic large cell lymphoma with extranodal involvement in the thigh muscle. The involvement of such a rare organ may lead to initial misdiagnosis and a delay in the onset of treatment.
authors.affiliation: Department of Orthopedic Surgery, Sapporo Medical University School of Medicine, West 16, South 1, Chuo-ku, Sapporo, Hokkaido 060-8543, Japan. emrmkt@yahoo.co.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Emori
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Kaya
authors.forename: Shigeo
authors.initials: S
authors.lastname: Takahata
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Tobioka
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Minaki
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Yamashita