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.
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 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.
['Agaimy|Abbas|A|', 'Vassos|Nikolaos|N|', 'Wunsch|Peter H|PH|', 'Hohenberger|Werner|W|', 'Hartmann|Arndt|A|', 'Croner|Roland S|RS|']
D000328:Adult D000368:Aged D000369:Aged, 80 and over D005260:Female D005770:Gastrointestinal Neoplasms D046152:Gastrointestinal Stromal Tumors D006801:Humans D008297:Male D008875:Middle Aged D009362:Neoplasm Metastasis D010534:Peritoneal Neoplasms D012189:Retrospective Studies D012307:Risk Factors D012704:Serous Membrane D055815:Young Adult
peritoneal spread Gastrointestinal stromal tumors macroscopic classification GIST serosa penetration