Immunophenotype of sporadic and familial adenomatous polyposis associated fundic gland polyps: a mucin and MIB1 study.
BACKGROUND
Fundic Gland Polyps (FGPs) are small sessile (2-5 mm) usually multiple polyps arising in the gastric, acid-secreting mucosa, described both in a sporadic form, prevalently in middle aged females, and associated with familial adenomatosis coli (FAP)-Gardner's syndrome and their attenuated variants (syndromic form).


OBJECTIVE
We performed an immunohistochemical study on 5 syndromic (4 cases without and 1 case with dysplasia) and 28 sporadic FGPs, using monoclonal antibodies (MoAbs) against normal epitopes of fundic mucosa (Ck20, the surface gastric mucin M1, EMA, ChA), H. pylori and HLA-DR(Ia) antigens, CEA and mucin epitopes, and the Ki67 (MIB1) proliferation antigen, in order to establish the immunophenotype of FGPs; find any possible differences between sporadic and syndromic polyps.


RESULTS
Ck20 and M1 were positive on surface and foveolar epithelium of controls, whereas sporadic and syndromic FGPs showed an enhanced deep positivity below foveolar necks ("foveolar metaplasia"); EMA was strongly positive on parietal cells, highlighting intracytoplasmic canaliculi. Chromogranin-positive cells in FGPs were alike controls, except for a sporadic case with micronodular hyperplasia. Ck7, as expected, was negative in controls, whereas the 5 syndromic FGPs and 25 of 28 sporadic FGPs showed a diffuse superficial and deep expression. H. pylori anti-serum gave negative results on all cases, and only 3 sporadic FGPs showed epithelial expression of HLA-DR(Ia). Syndromic FGPs were CEA negative, whereas 32% of sporadic FGPs expressed it. FGPs showed a neoexpression of the mucin oncofetal epitopes syalil-Tn (3/5 syndromic, 82% sporadic) CA19.9 and CA50 (4/5 syndromic, 14% sporadic). MIB1-labelling index of surface (30.5%) and deep (37.1%) compartments of the 4 syndromic FGPs without dysplasia was enhanced, with high statistical significance (p < 0.0001) both in comparison to controls (16.9% superficial stain only) and sporadic FGPs (15.8% surface, 19.5% deep labeling indexes). Moreover, the MIB1 labeling-index of the syndromic case with dysplasia (60.8% surface, 56.6% deep labeling indexes) was further enhanced in comparison with the other 2 syndromic cases.


CONCLUSIONS
Sporadic and syndromic FGPs showed a neoexpression of Ck7, CEA, and mucin epitopes. As these markers are normal antigens of fetal stomach, FGPs showed a fetal, "immature" immunophenotype. The only difference we found between syndromic and sporadic polyps was a statistically significant enhanced MIB1-labelling index expression by syndromic FGPs, further enhanced in the syndromic FGP with dysplasia.
Declich
Paolo
P
Service of Pathology, Rho Hospital, Italy. paolo.declich@libero.it
Carneiro
Fátima
F
Omazzi
Barbara
B
Tavani
Enrico
E
Grassini
Roberta
R
Ferrara
Aldo
A
Bortoli
Aurora
A
Bellone
Stefano
S
Gozzini
Claudio
C
Prada
Alberto
A
D011125:Adenomatous Polyposis Coli / Q000378:metabolism* / Q000473:pathology; D018256:Adenomatous Polyps / Q000378:metabolism* / Q000473:pathology; D000328:Adult; D005260:Female; D005748:Gastric Fundus / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D016130:Immunophenotyping; D019394:Ki-67 Antigen / Q000378:metabolism*; D008297:Male; D009077:Mucins / Q000378:metabolism*
D019394:Ki-67 Antigen; D009077:Mucins