title: Coexistence of gastrointestinal stromal tumours (GIST) and malignant neoplasms of different origin: prognostic implications.
abstract: BACKGROUND
  Over the past decade, several changes occurred in diagnostics, treatment and understanding of pathogenesis of gastrointestinal stromal tumours (GIST). However, their coexistence with other malignancies of different histogenetic origin remains a challenging issue.
  
  
  METHODS
  Patients diagnosed with GIST in a 10-years period were identified retrospectively and clinical history and findings thoroughly explored for the presence of associated other malignancies. Follow up data were obtained and analysed for prognostic impact of the concurrent malignancy and/or GIST.
  
  
  RESULTS
  Thirty seven (27 males, 10 females) of 86 GIST-patients (43%) had another malignancy. Mean age was 70 years. Associated malignancies were gastrointestinal (n = 29; 69%), renal-/urological (n = 5; 12%), haematological (n = 4; 9.5%), cutaneous (n = 3; 7%) and thyroid (n = 1; 2.5%) in origin. Majority of GISTs occurred in stomach (65%) and small intestine (30.6%) and most (78%) were asymptomatic incidental findings during diagnostic or therapeutic procedures for associated malignancies. GIST size ranged from 0.1 cm to 9 cm (mean, 2.2 cm) and all of them had a low (<5/50 HPFs) or no mitotic activity. Thirty-one tumours (84%) were of no/very low/low risk and 6 were of intermediate risk. During follow-up (range 3-160 months, mean; 60 months), one patient suffered from distant metastases of GIST. Seven patients (19%) died of associated malignancies and three patients (8%) of other non-tumour-associated cause, but none died of GIST.
  
  
  CONCLUSIONS
  Coexistence of GIST with other malignancies is higher than previously reported and should draw attention of clinicians towards these incidental findings. Prognosis in these patients is usually determined by other malignancy and not significantly influenced by GIST. Therefore treatment algorithms should be focused on prognostically relevant malignancy.
authors.affiliation: Department of Surgery, University Hospital, Erlangen, Germany. Electronic address: nikolaos.vassos@uk-erlangen.de.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Vassos
authors.affiliation: Department of Pathology, University Hospital, Erlangen, Germany.
authors.forename: Abbas
authors.initials: A
authors.lastname: Agaimy
authors.affiliation: Department of Surgery, University Hospital, Erlangen, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Hohenberger
authors.affiliation: Department of Surgery, University Hospital, Erlangen, Germany.
authors.forename: Roland S
authors.initials: RS
authors.lastname: Croner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000473:pathology*; D046152:Gastrointestinal Stromal Tumors / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D011379:Prognosis; D012306:Risk
keywords: Coexistence; GIST; Gastrointestinal stromal tumour; Imatinib mesylate; Malignancy