Clinicopathological features of a kindred with SCG5-GREM1–associated hereditary mixed polyposis syndrome

Publication date: February 2017
Source:Human Pathology, Volume 60
Author(s): Thomas Plesec, Kathryn Brown, Charles Allen, Carol A. Burke, James Church, Matthew Kalady, Lisa LaGuardia, Margaret O'Malley, Brandie Heald
Since first characterized in 1997, patients with hereditary mixed polyposis syndrome (HMPS) have been difficult to identify because of lack of well-established diagnostic criteria. Recently, HMPS was found to be caused by a duplication on chromosome 15 spanning the 3′ end of the SCG5 gene and a region upstream of the GREM1 locus. Clinical testing for the duplication is available; however, the clinical characteristics of hereditary mixed polyposis to support testing are ill defined. The clinicopathological findings of 10 HMPS patients with confirmed germline SCG5-GREM1 duplication were reviewed. Mean age at presentation was 33.3 years. Fifty-one colonoscopies yielded 207 polyp specimens, all of which were reexamined. Adenomas (n = 80) and a fairly unique polyp composed of a mixture of hyperplastic polyp and inflammatory polyp–type changes (n = 74) were the most common findings; however, other polyps, including hyperplastic (n = 28), mixed inflammatory polyp/adenoma (n = 8), inflammatory polyp (n = 7), prolapse-type polyp (n = 6), and lymphoid aggregates (n = 4), were encountered. None of the patients developed colorectal malignancy during surveillance, demonstrated extracolonic manifestations, or underwent colectomy on follow-up (mean, 26.2 years). SCG5-GREM1 duplication–associated polyposis is characterized by a few polyps per endoscopy with a mixture of phenotypes, most commonly adenoma and nondysplastic mixed hyperplastic/inflammatory polyps. Nine of 10 patients had at least 1 mixed hyperplastic-inflammatory polyp, which is the characteristic lesion of SCG5-GREM1 duplication–associated HMPS.



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