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Int J Clin Exp Pathol 2012;5(1):12-22

Original Article
Impact of serosal involvement/extramural growth on the risk of synchronous and
metachronous peritoneal spread in gastrointestinal stromal tumors: Proposal for a
macroscopic classification of GIST

Abbas Agaimy, Nikolaos Vassos, Peter H. Wünsch, Werner Hohenberger, Arndt Hartmann, Roland S. Croner

Institute of Pathology and Department of Surgery, University Hospital, Erlangen, Germany; Institute of Pathology, Nürnberg City Hospital,
Nürnberg, Germany.

Received December 8, 2011; accepted December 20, 2011; Epub January 1, 2011; published January 15, 2012

Abstract: Background: Peritoneal and hepatic metastases are the main routes of spread of gastrointestinal stromal tumors (GIST). However,
criteria to predict the site and pattern of recurrence in individual cases are still lacking. Patients: We retrospectively analyzed 67 consecutive
GISTs with complete gross descriptions to correlate macroscopic patterns with clinical course. Primary endpoint was the appearance of
synchronous or metachronous peritoneal disease. Tumors were classified into type I (luminal/intramural) and type II (extramural) based on the
macroscopic/histologic presence or absence of normal tissue between deeper tumor border and serosa, respectively. Results: Patients were
35 men and 32 women (mean age, 64 yrs) with gastric (n=32), small bowel (n=30) and large bowel (n=5) GISTs. Based on the above proposal,
22 tumors were classified as type I and 45 as type II. Type I tumors were predominantly gastric (18/22; P<0.001) and frequently had very low/low
risk (14/22; P<0.001) whereas type II tumors were predominantly intestinal (31/45; P<0.001) and often of intermediate/high risk (36/45;
P<0.001). Ten patients had synchronous peritoneal spread (n=10) and 6/30 patients with a mean follow-up of 29 months developed
metachronous peritoneal spread at a mean of 27 months. Tumor rupture was seen in 2 patients (3%). Thus, 16/40 patients (40%) had
synchronous or metachronous peritoneal progression. Taken by gross type, peritoneal progression was seen in 15/30 type II compared to 1/10
type I tumors (p=0.032). Conclusion: this study points to extramural growth as a predictor of peritoneal recurrence in GIST, probably as a
consequence of tumor rupture or due to microscopic serosal penetration. This study aimed at alerting surgical pathologists to the importance
of careful gross and microscopic assessment of resection specimen harboring GIST to allow for reliable prospective evaluation of serosal
involvement as an adverse prognostic factor in GIST.

Keywords: Gastrointestinal stromal tumors; GIST; macroscopic classification; serosa penetration; peritoneal spread

Address all correspondence to:
Abbas Agaimy, MD
Pathologisches Institut
Universitätsklinikum Erlangen
Krankenhausstraße 10
91054 Erlangen
Tel: +49-9131-85-22288
Fax: +49-9131-85-24745
E-mail: abbas.agaimy@uk-erlangen.de