Microsatellite instability in sporadic colorectal carcinoma is not an indicator of prognosis

Fifty sporadic colorectal carcinomas diagnosed in 1991 were anal, scd for m icrosatellite instability at four loci. Five of 50 (10 per cent) tumours sh owed replication errors (RERs) at two or more loci and were classed as RER- positive (RER+). A further five showed RERs at one locus only. A significan t association (Fisher exact test) was found between RER+ rumours and locati on in the proximal colon, exophytic shape, size >5 cm, histological margin, lymphoid reaction, and near-diploid DNA content, There nas no significant difference for age, ses, grade, mucin production, p53 protein overexpressio n or Duke's stage. There was no significant difference in survival as measu red over a 60-month follow-up period. The findings, though Limited by the s mall case numbers involved, show an association between RER positivity. in sporadic colorectal tumours and certain clinico-pathological features. They do not suggest a better clinical outcome for sporadic RER+ rumours. Copyri ght (C) 1999 John Wiley & Sons, Ltd.