Gastrointestinal Pathology
Lynch syndrome testing—when and how?
Expression of the Intestinal Marker Cdx2 in Secondary
Clinical significance of signet-ring cells in colorectal mucinous adenocarcinoma
Lynch syndrome testing—when and how?
Of the approximately 150,000 people who develop colorectal cancer each year, the vast majority are sporadic cases. But a few percent of colorectal cancer cases occur in people who have a genetic predisposition. Most of those with a genetic predisposition don't know they are carrying a genetic defect that greatly increases their risk of colorectal cancer and a few other selected cancers. "Until recently, there has not been a way, other than family history, to readily identify these individuals," says Stephen N. Thibodeau, PhD. "Now there is." Dr. Thibodeau, who is co-director of the clinical molecular genetics laboratory at the Mayo Clinic and professor of laboratory medicine and pathology at Mayo Medical School, gave a presentation on this procedure, called microsatellite instability, or MSI, testing, at the 2006 Association for Molecular Pathology meeting.
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Expression of the Intestinal Marker Cdx2 in Secondary
Secondary adenocarcinomas of the large bowel can closely mimic primary tumors. The differentiation of secondary from primary adenocarcinomas of the colorectum, however, is important because their clinical management and prognosis are different. Immunostaining with the nuclear transcription factor Cdx2, expressed in normal intestinal epithelia and colorectal adenocarcinomas, could be of potential diagnostic use.
The Cdx2 gene is an intestinal transcription factor involved in the proliferation and differentiation of intestinal epithelial cells. Previous studies showed that Cdx2 is expressed in normal and neoplastic intestinal epithelial cells with a relatively high sensitivity and specificity and that it can be used as an immunohistochemical marker for neoplasms of intestinal origin.5–9 To our knowledge, the reactivity of Cdx2 in adenocarcinomas metastatic to the large bowel has not been yet studied.
Clinical significance of signet-ring cells in colorectal mucinous adenocarcinoma
Mucin occasionally accumulates intracellularly in colorectal mucinous adenocarcinomas, resulting in signet-ring cell morphology. In the current practice of pathology, there is no definitive rule on how to report a minor component of signet-ring cells in colorectal mucinous adenocarcinomas. We hypothesized that the absence of signet-ring cell component might have a favorable effect on survival of mucinous adenocarcinoma patients. To assess the biological characteristics of colorectal mucinous adenocarcinoma, we analyzed its clinicopathological features, microsatellite instability status, and survival outcomes and compared them with those of colorectal signet-ring cell carcinoma. A total of 266 consecutive colorectal mucinous adenocarcinoma patients and 65 signet-ring cell carcinoma patients were included. Mucinous adenocarcinomas, by comparison with signet-ring cell carcinomas, were characterized by development at an older age, less frequent vascular invasion and lymph node metastasis, and lower TNM stage at presentation. A total of 21 (22%) of 95 mucinous adenocarcinomas and 12 (19%) of 63 signet-ring cell carcinomas were high-frequency microsatellite instability.