[630] Microsatellite Unstable Barrett's Esophagus-Associated Adenocarcinomas Are Rare, but Clinicopathologically Similar to the Colonic Counterpart

EG Demicco, AB Farris, AJ Iafrate, HA Gaissert, J Fukuoka, C Cohen, LR Zukerberg, GY Lauwers, M Mino-Kenudson. Massachusetts General Hospital, Boston; Emory University, Atlanta; Toyama Medical University, Toyama, Japan

Background: The frequency of microsatellite instability (MSI) has been reported inconsistently in Barrett's esophagus-associated adenocarcinoma (BEAd), and little is known about the clinicopathologic features of MSI high BEAds.
Design: Seventy-nine BEAds consecutively resected between 2000 and 2007 with available tissue blocks were evaluated by immunohistochemistry for MLH1, MSH2, MSH6 and PMS2 (MSI IHC). No cases underwent neoadjuvant therapy. Complete negative expression in any of the markers was considered to be positive. Several clinicopathologic features were examined in MSI IHC positive cases, and compared with those of MSI IHC negative cases.
Results: The study cases consisted of 69 males and 10 females with a mean age of 65 years. AJCC tumor and lymph node stages were pT1/2/3/4 = 35/10/33/1 and pN0/1/2/x = 45/31/2/1; the mean tumor size was 3.6 cm (4.7 cm for non-T1 tumors). Of those, 5 (6%) cases showed MLH1 and PMS2 loss. 3 of the 5 cases were further examined by PCR and were confirmed to have high-level MSI. Table 1 summarizes the clinicopathologic features of the 5 cases.

Table 1
Age (yrs)GenderTumor size (cm)pTpNHistologyFollow-up (mo)Status
80F8.042heterogeneous with medullary14.8dead of disease
79M5.531heterogeneous with mucinous and signet ring cells22.7dead of disease
75M7.531medullary0.5dead of complication
67M2.820poorly differentiated with signet ring cells10.7dead of unknown cause
78F6.030medullary3.0lost to follow-up

Compared to MSI IHC negative cases, the MSI IHC positive BEAds were associated with older age (p < 0.005), larger tumor size (p = 0.15 for non-T1 tumors) and more advanced T stage (p = 0.15). The morphology of the MSI IHC positive tumors was heterogeneous with medullary, mucinous and/or signet ring cell features recapitulating the colonic counterpart.
Conclusions: Microsatellite instability is rare in BEAds, but is associated with clinicopathologic features similar to the colonic counterpart such as mucinous, medullary, or signet ring cell features. Because of its scarcity, the survival impact of MSI is yet undetermined. Additional larger scale studies are warranted.
Category: Gastrointestinal

Wednesday, March 24, 2010 9:30 AM

Poster Session V # 69, Wednesday Morning


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