title: Extranodal lymphoma originating in the gluteal muscle with adjacent bone involvement and mimicking a soft tissue sarcoma.
abstract: BACKGROUND
  Extranodal lymphoma (ENL) in the muscles is a rare manifestation of non-Hodgkin lymphoma (NHL). The aim of this case report is to describe and evaluate the clinical presentation and important radiologic features of ENL affecting the musculoskeletal system.
  
  
  METHODS
  We present a 52-year-old female with a 3-week history of left gluteal pain. Computed tomography (CT) showed a non-uniformly early enhancing mass in the left gluteal muscle, the tumor demonstrating central necrosis and adjacent bone involvement. Fluorine-18 fluorodeoxyglucose positron emission tomography ((18)F-FDG PET)/CT showed areas of increased (18)F-FDG uptake in the left gluteal musculature, pelvic bones, para-aortic and mediastinal lymph nodes and both lungs. Histopathological examination showed a diffuse large B cell lymphoma (DLBCL). After 8 cycles of R-CHOP chemotherapy, the mass in the left gluteal muscle has completely disappeared
  
  
  CONCLUSIONS
  Although destructive tumor originating in the gluteal muscle with adjacent bone involvement is more common in soft tissue sarcoma, lymphoma should be regularly included in the differential diagnosis. While CT is a useful modality for assessing soft tissue masses, disruption and injury of the surrounding tissues, PET/CT fusion is superior for the detection of unexpected extranodal sites of disease, or for exclusion of disease in the presence of nonspecific extranodal CT findings.
  
  
  CONCLUSIONS
  A rapid growth pattern and destructive masses that invade adjacent structures on CT are key findings of DLBCL, and (18)F-FDG PET/CT is a useful imaging modality to accurately determine the disease stage and disease aggressiveness of NHL.
authors.affiliation: Department of Surgery, Okinawa Prefectural Hokubu Hospital, Okinawa, Japan. Electronic address: morihiro@bj8.so-net.ne.jp.
authors.forename: Morihiro
authors.initials: M
authors.lastname: Katsura
authors.affiliation: Department of Internal Medicine, Okinawa Prefectural Hokubu Hospital, Okinawa, Japan. Electronic address: carrot_and_whip_hiro@yahoo.co.jp.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Nishina
authors.affiliation: Department of Radiology, Okinawa Prefectural Hokubu Hospital, Okinawa, Japan. Electronic address: shigemori-sin@umin.ac.jp.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shigemori
authors.affiliation: Department of Pathology and Cell Biology, University of the Ryukyus, Graduate School of Medicine, Okinawa, Japan. Electronic address: h097509@med.u-ryukyu.ac.jp.
authors.forename: Takaya
authors.initials: T
authors.lastname: Nakanishi
keywords: Diffuse large B cell lymphoma; Extranodal lymphoma; Gluteal mass; PET