Very Well-differentiated Gastric Carcinoma of Intestinal Type

Tetsuo Ushiku; Thomas Arnason; Shinichi Ban; Tsunekazu Hishima; Michio Shimizu; Masashi Fukayama; Gregory Y Lauwers

Disclosures

Mod Pathol. 2013;26(12):1620-1631. 

In This Article

Materials and Methods

Case Selection

We identified a series of 21 very well-differentiated gastric adenocarcinomas of intestinal metaplasia type obtained from the pathology archives of the authors' institutions and from the consultation files of two of the authors (SB and MF). All cases met the criteria put forward previously.[1,5] In brief, very well-differentiated gastric adenocarcinomas of intestinal type are composed of neoplastic epithelium with low-grade nuclear atypia, differentiating toward metaplastic intestinal type cells, such as absorptive cells, goblet cells, Paneth cells, and of simple tall mucin-producing cells akin to foveolar-type epithelia. Architecturally, glandular structures are commonly seen with tortuousness, branching, or anastomosing, recapitulating the shapes of the letters W, H, Y, or X at low-power view. Characteristically, the neoplastic glands are usually sparsely distributed and lack back-to-back crowding. All 21 cases were reviewed by four pathologists to confirm the diagnosis of very well-differentiated adenocarcinoma of intestinal type.

The study was approved by the Institutional Review Board of the Massachusetts General Hospital.

Clinical Data

Demographic data, endoscopic findings, and clinical follow-up were obtained by review of the medical records. The macroscopic type of tumor was classified according to the criteria in the World Health Organization classification for early gastric cancer and the Borrmann classification for advanced gastric cancer.[7]

Histologic Assessment

Hematoxylin and eosin-stained sections were available in all cases and were evaluated for size of the lesion, depth of invasion, lymphovascular invasion, and lymph node metastasis in the 11 cases surgically resected. The presence or absence of a set of architectural, nuclear, cytomorphologic, and stromal features in each case were systematically recorded according to the consensus opinion of two study pathologists using a multiheaded microscope. Independent reviews of the cases for the diagnostic criteria were not performed and consequently interobserver variability in the assessment of these features was not determined. The architectural features that were assessed included tortuosity, branching, anastomosing, distention, abortive and spiky glandular patterns, glandular outgrowth, and discohesive neoplastic cells. Branching glands were defined as structures dividing downward, and typically demonstrating an inverted Y-shaped pattern, whereas anastomosing glands were laterally connected (H- or X-shaped) or fused downward (W- or Y-shaped). A spiky gland was defined as a glandular structure with sharp edges or sharp projections (Figure 1). Glandular outgrowth was defined as the presence of a very small glandular structure emerging from a larger gland (Figure 1).

Figure 1.

Representative examples of tortuous glands (a), a branching gland (b), anastomosing glands (c), a distended gland (d), spiky glands (e), and glandular outgrowth (f) in very well-differentiated adenocarcinoma of intestinal type.

Cytomorphologic features that were evaluated included the presence of normal and dystrophic goblet cells, foveolar epithelium, absorptive cells, and Paneth cells. We also assessed the presence of altered nuclear features: nuclear enlargement, hyperchromasia, clearing of chromatin, prominent nucleoli, mitotic rate, and presence of atypical mitoses. Finally, stromal features were reviewed, such as quality of the lamina propria, that is, myxoid change, stromal edema, desmoplasia, inflammation, and vascular ectasia. For cases with submucosal or advanced invasion, mucosal and deeper invasive components were evaluated separately.

Each feature was recorded semiquantitatively by evaluating the proportion of the involved area over the entire lesion as follows: absent; 1+ (present in <25% of lesion), 2+ (present in 25–50% of lesion), and 3+ (present in >50% of lesion).

Immunohistochemical Analysis

Formalin-fixed paraffin-embedded tissue blocks were available in all 21 cases. To determine the tumor phenotype, immunohistochemical staining was performed using antibodies for MUC2 (CLH2, 1:500, Novocastra Laboratories, Newcastle, UK), CD10 (56C6, 1:100, Novocastra Laboratories), CDX-2 (CDX-2-88, 1:100, Biogenex, San Ramon, CA), MUC5AC (CLH5, 1:500, Novocastra Laboratories), and MUC6 (Ccp58, 1:500, Novocastra Laboratories). In brief, 5 μm sections were deparaffinized and hydrated through a graded series of alcohol. Following antigen retrieval in 10 mM citrate buffer (pH 6.0) in a microwave oven for 10 min, inhibition of endogenous peroxidase activity was performed by immersion in a 3% H2O2/methanol solution. The sections were then incubated with the primary antibodies, thoroughly washed in phosphate-buffered solution, and incubated with a biotinylated secondary antibody, followed by treatment with the avidin-biotinylated horseradish peroxidase complex (Vectastain Elite ABC kit, Vector Laboratories, Burlingame, CA). The sections were developed using DAB (3,3-diaminobenzidinetetrachloride) as the chromogen. Nuclear counterstaining was accomplished using Mayer's hematoxylin.

Cytoplasmic staining for mucin core proteins and apical membranous staining for CD10 were evaluated. For CDX-2, only nuclear staining was considered positive. The tumor was defined as positive for each marker when >10% of the neoplastic cells were stained. Tumors were categorized into gastric or intestinal phenotypes if they were positive for gastric (MUC5AC or MUC6) or intestinal (MUC2, CD10 or CDX-2) markers, respectively. Tumors were classified as mixed type when both gastric and intestinal markers were positive, and tumors were classified as null type when both markers were negative.[8]

Evaluation of Pre-resection Biopsies

Pretreatment biopsy specimens were available in 18 patients. Whether the very well-differentiated gastric adenocarcinoma was present in each biopsy was evaluated by comparing the biopsies with the corresponding resection specimens. We evaluated each diagnostic biopsy for the cytoarchitectural features described above. The time interval between the initial biopsy and resection, the number of endoscopic procedures performed, the total number of biopsy fragments, and the original diagnosis for each biopsy were also recorded.

Statistical Analysis

Continuous variables were compared using the Student's t-test and categorical variables were compared using Fisher's exact test or χ2- test (Excel Statistics, SSRI, Tokyo, Japan). Differences were considered to be significant if the P-value from the two-tailed test was <0.05.

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