title: Presacral extramedullary haematopoiesis: A diagnostic update and case report of a late diagnosis.
abstract: BACKGROUND
  We report a rare case of presacral extramedullary haematopoiesis, which manifested as a tumoural mass on a routine ultrasonography in a patient presenting with symptoms of cholecystitis. Since Ask-Upmark in 1945 reported 3 cases of pelvic extramedullary haematopoiesis, we are aware of only published 14 additional cases.
  
  
  METHODS
  A 73-year-old female patient presented with abdominal pain in the right hypochondrium. An abdominal ultrasonography revealed cholecystitis with cholecystolithiasis and a coincidental hyperreflective mass of 9.5cm was visualised behind the bladder. A clinical examination identified a mass in the pelvis that could be palpated vaginally. A computerised tomography scan showed a large presacral, inhomogeneous, multilobular and nodular tumour. The patient was admitted for laparoscopic resection of the gall bladder and laparoscopic exploration of the presacral mass. An anatomopathological examination of the tissue revealed the presence of extramedullary haematopoietic tissue. A postoperative haematological investigation indicated that the extramedullary haematopoiesis was idiopathic.
  
  
  CONCLUSIONS
  Presacral EMH may occasionally present with symptoms of nerve compression. Symptoms of haematologic disorders may accompany EMH. Barium enema, abdominal ultrasound, CT scan, MRI and radionuclide bone marrow imaging have all been used by previous authors in establishing the diagnosis. Tissue samples may be misdiagnosed when atypical megakaryocytes are misinterpreted as malignant cells, which occurred in this case. Misdiagnosis can occur even more often when EMH is not considered in the differential diagnosis due to its rare occurrence. In this case, the final diagnosis was made tissue sampling after surgery. Treatment of EMH is only necessary when it is symptomatic.
  
  
  CONCLUSIONS
  This case report shows that extramedullary haematopoiesis is very rare and that it is a difficult diagnostic challenge when its location is unusual and when it is not associated with a haematologic disorder. Together with this case report, we present an update of the available diagnostic methods.
authors: Department of Surgery and Anatomopathology, AZ KLINA, Augustijnslei 100, 2930 Brasschaat, Belgium.
authors: Erwin
authors: E
authors: Denies
authors: Valerie
authors: V
authors: Duwel
authors: Peter
authors: P
authors: Delvaux