Gastric and small intestinal traditional serrated adenomas: a detailed morphologic and immunohistochemical analysis

Abstract

Background/aims: Traditional serrated adenomas (TSAs), despite their low incidence in colorectum, may originate in other parts of the gastrointestinal (GI) tract, including stomach and small intestine. Malignant transformation for upper GI TSAs has recently been reported in the literature. Here, we present a series of gastric and small intestinal TSAs with the aim to characterize their morphologic and immunophenotypic features as well as their neoplastic potential in a compartmental manner using digitalized images.

Materials and methods: The study comprised 12 GI polyps with TSA features-5 gastric and 7 small intestinal. The extent of the characteristic features of TSA, including eosinophilic cells, ectopic crypt foci (ECF), slit-like serration, foveolar epithelium, goblet cells, together with dysplastic-carcinomatous foci were assessed on digitalized H-E images and were used as reference for immunohistochemical analysis.

Results: All polyps in the cohort contained eosinophilic cells as the most extensive morphologic feature followed by ECF and slit-like serration in decreasing order. Serrated dysplasia was more common in gastric polyps, which more frequently showed neoplastic progression compared with the intestinal ones. CK20 was the most widely expressed marker with a preference to eosinophilic cells while ECFs were mostly negative. Ki67 showed the opposite pattern of CK20. MUC6 and MUC2 were selectively expressed in the basal zone and goblet cells, respectively.

Conclusion: Our results showed that the presence of eosinophilic cells with pencillate nuclei commonly accompanied by ECF and slit-like serration are the defining features of gastric and small intestinal TSAs. They frequently harbor neoplastic foci, particularly in gastric location where serrated dysplasia seems to be more common.

Figure 1

A gastric TSA; panaromic view with complex crypt architecture and villous surface (H&E, ×20)

Figure 2

Ectopic crypts (H&E, ×100)

Figure 3

Eosinophilic cells with mid-zonal pencillate nuclei, ectopic crypts and scattered goblet cells (H&E, ×100)

Figure 4

Slit-like serration and gastric foveolar epithelium (H&E, ×200).

Figure 5

Dysplastic area and abrupt transition from eosinophilic cells to HG dysplasia (H&E, ×100).

Figure 6

A small intestinal TSA; panaromic view with complex crypt architecture and villous surface (H&E, ×17)

Figure 7

Eosinophilic cells with mid-zonal pencillate nuclei and numerous ectopic crypts in a small intestinal TSA (H&E, ×130)

Figure 8

Neoplastic cells with severe cytologic atypia in a small intestinal TSA (H&E, ×400).

Figure 9

Ki67 emphasizes the high proliferation rate in ectopic crypts compared with eosinophilic cells, which are scarcely positive (IHC, ×81).

Figure 10

CK20 shows the opposite pattern of Ki67 with a high affinity to the eosinophilic cell compartment (IHC, ×79).

Figure 11

MUC6 is predominantly expressed in basal zone (IHC, ×37).

Figure 12

MUC2 highlights goblet cell compartment (IHC, ×105).

Figure 13

High-grade dysplastic foci harboring intramucosal carcinoma (H&E, ×120).

Figure 14

High expression of p53 in the dysplastic foci (IHC, ×156).

Figure 15

p16 is lost in the neoplastic compartment (IHC, ×129).