Measuring Histologic Activity in Inflammatory Bowel Disease: Why and How.

Histology is used to confirm the diagnosis of inflammatory bowel disease, exclude superimposed infections, and to evaluate for dysplasia. Histology has rarely been used to measure disease activity and guide therapy despite evidence that histologic measurements have value in predicting important clinical outcomes. More recently, there have been numerous studies supporting a role for histologic disease activity measurements in predicting a variety of outcomes including relapse, hospitalizations, steroid use, and dysplasia. The histologic assessment was superior to endoscopic measurements in many of these studies. This review will summarize the recent literature regarding histologic disease activity measurements in ulcerative colitis and Crohn disease. A detailed description of histologic scoring systems will also be provided to provide pathologists with the necessary tools to accurately measure disease activity.

Loss of SATB2 Expression Is a Biomarker of Inflammatory Bowel Disease-associated Colorectal Dysplasia and Adenocarcinoma.

SATB2 is a sensitive immunohistochemistry marker of colorectal carcinoma and non-neoplastic colorectal epithelium that is complementary to CDX2. However, its expression is affected by molecular alterations. Inflammatory bowel disease-associated neoplasia demonstrates molecular alterations that are different from those in sporadic colorectal neoplasia. Given these differences, we examined SATB2 expression in 73 cases of inflammatory bowel disease-associated neoplasia including 37 dysplasia cases and 36 carcinomas and compared the expression patterns with 50 cases of nondysplastic colorectal mucosa in patients with active inflammatory bowel disease, 40 sporadic colonic polyps (20 conventional adenomas and 20 sessile serrated lesions/polyps), and 343 sporadic colorectal adenocarcinomas to assess SATB2 immunohistochemistry as a biomarker of inflammatory bowel disease-associated neoplasia. Loss of SATB2 expression was only identified in colorectal dysplasia arising in inflammatory bowel disease (15/37, 41%) and was not seen in nondysplastic colorectal mucosa with active inflammatory bowel disease or sporadic colonic polyps (P<0.001). Loss of SATB2 expression was identified in both endoscopically visible dysplasia (11/28, 39%) and invisible (4/9, 44%) dysplasia. Loss of SATB2 expression was identified in 67% (24/36) of inflammatory bowel disease-associated carcinomas and was significantly more frequent compared with sporadic colorectal carcinomas (47/343, 14%, P<0.001). There was no difference in positive CDX2 expression between inflammatory bowel disease-associated colorectal carcinoma and sporadic colorectal carcinoma (89% vs. 85%, P=1.0). In conclusion, loss of SATB2 expression is common in inflammatory bowel disease-associated colorectal dysplasia and adenocarcinoma and may be a helpful ancillary biomarker when evaluating for inflammatory bowel disease-associated dysplasia.

SATB2 Is Superior to CDX2 in Distinguishing Signet Ring Cell Carcinoma of the Upper Gastrointestinal Tract and Lower Gastrointestinal Tract.

Signet ring cell carcinomas of the gastrointestinal (GI) tract are clinically aggressive neoplasms with frequent intra-abdominal metastases at initial presentation. Currently available immunohistochemistry (IHC) markers cannot distinguish signet ring cell carcinomas of the lower GI tract and upper GI tract, suggesting the need for more specific diagnostic markers. SATB2 is a novel, sensitive marker for colorectal carcinoma. We hypothesized that SATB2 IHC can reliably identify primary and metastatic signet ring cell carcinomas of lower GI tract origin. SATB2 and CDX2 IHC was performed on 159 primary (n=93) and metastatic (n=66) signet ring cell carcinomas of GI tract origin and 13 metastatic breast carcinomas with signet ring cell features. Positive SATB2 expression (SATB2) was identified in 82% (27/33) of appendiceal, 88% (43/49) of colorectal, 13% (7/54) of gastric, and 35% (8/23) of esophageal/esophagogastric junction signet ring cell carcinomas. Primary and metastatic signet ring cell carcinomas of lower GI tract origin were more frequently SATB2 than those from upper GI tract (70/82, 85% vs. 15/77, 19%, P<0.01). Compared with CDX2, SATB2 and dual-positive staining for SATB2 and CDX2 both had higher specificities for signet ring cell carcinomas from the lower GI tract (81% vs. 49% and 86% vs. 49%, respectively, P<0.01 for both). Two (15%) metastatic breast carcinoma were SATB2, but all 13 demonstrated negative CDX2 staining. In summary, our results show SATB2 is a relatively specific immunohistochemistry marker for both metastatic and primary signet ring cell carcinomas of lower GI tract origin.

Loss of SATB2 Expression in Colorectal Carcinoma Is Associated With DNA Mismatch Repair Protein Deficiency and BRAF Mutation.

The special AT-rich sequence binding protein (SATB2) has been reported to be a specific immunohistochemical marker for colorectal carcinoma; however, correlation of SATB2 expression with molecular alterations commonly assessed in colorectal carcinoma has not been performed. We examined the immunohistochemical expression of SATB2 in 586 adenocarcinomas of the gastrointestinal (GI) tract and pancreas to assess its utility in diagnosis and analyze the clinicopathologic and molecular characteristics of colorectal carcinoma stratified by SATB2 expression. SATB2 and CDX2 expression were evaluated in 266 adenocarcinomas of lower GI tract origin (246 colorectal and 20 appendiceal mucinous), 208 adenocarcinomas of upper GI tract and small intestinal origin (74 esophagus/esophagogastric junction, 103 stomach, 20 duodenal, and 11 jejunoileal), and 112 pancreatic ductal adenocarcinomas. SATB2 expression was more frequently identified in adenocarcinomas of lower GI tract origin (222/266, 83%) compared with upper GI tract, small intestinal, or pancreatic origin (26/320, 8%) (P<0.001). Compared with CDX2 alone, dual positive expression for SATB2 and CDX2 (SATB2/CDX2) has a significantly higher specificity for adenocarcinoma of lower GI tract origin (94% vs. 57%, P<0.001). In colorectal carcinoma, loss of SATB2 expression was more frequently observed in DNA mismatch repair (MMR) protein deficient tumors (31%) compared with MMR protein proficient tumors (13%) (P<0.01). A BRAF V600E mutation was more frequently identified in colorectal carcinomas with loss of SATB2 expression compared with those with positive SATB2 expression (29% vs. 3%) (P<0.001). In summary, SATB2 expression is a relatively specific marker of lower GI tract origin; however, loss of SATB2 expression is more commonly seen in colorectal carcinoma with MMR protein deficiency and BRAF mutation.

Distinct Histopathologic and Molecular Alterations in Inflammatory Bowel Disease-Associated Intestinal Adenocarcinoma: c-MYC Amplification is Common and Associated with Mucinous/Signet Ring Cell Differentiation.

Background: Chronic idiopathic inflammatory bowel disease (IBD) is a significant risk factor for the development of intestinal adenocarcinoma. The underlying molecular alterations in IBD-associated intestinal adenocarcinoma remain largely unknown. Methods: We compared the clinicopathologic and molecular features of 35 patients with 47 IBD-associated intestinal adenocarcinomas with a consecutive series of 451 patients with sporadic colorectal carcinoma identified at our institution and published data on sporadic colorectal carcinoma. Results: c-MYC amplification was the most frequent molecular alteration identified in 33% of IBD-associated intestinal adenocarcinoma that is a significantly higher frequency than in sporadic colorectal carcinoma (8%) (P = 0.0001). Compared to sporadic colorectal carcinoma, IBD-associated intestinal adenocarcinomas more frequently demonstrated mucinous differentiation (60% vs 25%, P < 0.001) and signet ring cell differentiation (28% vs 4%, P < 0.001). Mucinous and signet ring cell differentiation were significantly associated with the presence of c-MYC amplification (both with P < 0.05). HER2 positivity (11%), KRAS exon 2 or 3 mutation (10%), and IDH1 mutation (7%) were less commonly observed in IBD-associated intestinal adenocarcinoma. There was an association between poor survival and HER2 status with 3 of 4 patients having HER2-positive adenocarcinoma dead of disease at last clinical follow-up; however, no statistically significant survival effect was identified for any of the molecular alterations identified. Conclusions: We demonstrate that IBD-associated intestinal adenocarcinomas have a high frequency of c-MYC amplification that is associated with mucinous and signet ring cell differentiation. Many of the identified molecular alterations have potential therapeutic relevance, including HER2 amplification, IDH1 mutation, and low frequency KRAS mutation.

Histologic Features Do Not Reliably Predict Mismatch Repair Protein Deficiency in Colorectal Carcinoma: The Results of a 5-Year Prospective Evaluation.

Most major professional medical organizations advocate universal screening for Lynch syndrome in colorectal carcinoma; however, some allow for a selective screening approach based on clinicopathologic factors including assessment of histologic features of mismatch repair protein deficiency (MMRD). We performed a prospective evaluation for histopathologic features of MMRD in colorectal carcinomas that underwent universal screening for Lynch syndrome to evaluate the ability of histology to predict MMRD. In total, 947 resected colorectal carcinomas over a 5-year period were prospectively analyzed for histologic features of MMRD and for DNA mismatch repair protein abnormalities. Histologic features of MMRD were reported as present in 281 of 947 (30%) tumors with only 109 (39%) cases demonstrating MMRD by immunohistochemistry. Histologic features of MMRD had a sensitivity of 74% [95% confidence interval (CI), 66%-80%], specificity of 78% (95% CI, 75%-81%), positive predictive value of 39% (95% CI, 32%-44%), and negative predictive value of 94% (95% CI, 92%-96%). Histologic features of MMRD in left colon/rectal tumors had a significantly lower sensitivity of 56% (95% CI, 41%-77%) compared with right colon tumors (P=0.02). Histologic rereview identified that tumor-infiltrating lymphocytes (TILs) were most likely to be incorrectly reported as absent, and 72% of cases incorrectly assessed as lacking TILs demonstrated MMRD by immunohistochemistry. We demonstrate that histologic features of MMRD do not reliably predict the presence of MMRD by immunohistochemistry. Interpretative errors in the assessment of histologic features of MMRD occur, particularly for TILs and in tumors of the left colon/rectum.

Site-specific Differences in Colonic Adenocarcinoma: KRAS Mutations and High Tumor Budding Are More Frequent in Cecal Adenocarcinoma.

Recent literature indicates that adenocarcinomas of the cecum differ with respect to molecular alterations compared with noncecal proximal colon adenocarcinomas and that cecal tumor site may be a prognostically relevant variable. We compared molecular alterations, histopathologic features, and disease-specific survival in a series of 328 colonic adenocarcinomas identified over a 2-year period and stratified by tumor location (cecum, right colon, and left colon). Overall, cecal adenocarcinomas demonstrated the highest frequency of molecular abnormalities with 74% harboring either a KRAS exon 2 or 3 mutation, a BRAF mutation, or DNA mismatch repair protein deficiency. KRAS mutations were more frequently seen in the cecum compared with all other tumor sites (P=0.03). KRAS mutations were identified in 46% of cecal adenocarcinomas compared with only 25% of adenocarcinomas of the right colon (P=0.004). Cecal adenocarcinomas more frequently displayed adverse histopathologic features, in particular high tumor budding (31%), compared with tumors of the right colon (18%; P=0.04) and tumors of the left colon (17%; P=0.02). Overall stage was the most important independent predictor of disease-specific survival in the multivariable analysis; however, cecal tumor site and high tumor budding were also predictive of poor survival, particularly in patients with stage III or IV tumors. In conclusion, cecal adenocarcinomas are characterized by a high frequency of KRAS mutations compared with noncecal right colon tumors, frequently display high tumor budding, and may be a prognostically relevant variable, particularly in patients with stage III or IV disease.

Small Bowel Adenocarcinoma Frequently Exhibits Lynch Syndrome-associated Mismatch Repair Protein Deficiency But Does Not Harbor Sporadic MLH1 Deficiency.

Universal screening for Lynch syndrome has been advocated for colorectal carcinoma but its utility in small bowel adenocarcinoma has not been reported. We analyzed a consecutive series of 71 small bowel adenocarcinomas identified over an 8-year period for DNA mismatch repair (MMR) protein expression to (1) compare the clinicopathologic features of small bowel adenocarcinoma stratified into MMR-deficient (MMRD) and MMR-proficient (MMRP) groups and (2) examine the patterns of MMR protein expression in small bowel adenocarcinoma compared with colorectal carcinoma. Six of 71 (8.5%) small bowel adenocarcinomas and 149 of 1291 (11.5%) colorectal carcinomas demonstrated MMRD. The 6 MMRD small bowel adenocarcinomas had the following expression pattern: 3 with concurrent loss of MSH2 and MSH6, 1 with isolated loss of MSH6, and 2 with concurrent loss of MLH1 and PMS2 in patients with a family history suggestive of genetic cancer susceptibility. Histopathology suggestive of MMR protein deficiency as proposed by the revised Bethesda guidelines was commonly seen in both MMRP (63%) and MMRD (67%) small bowel adenocarcinomas (P>0.05). MMRD small bowel adenocarcinoma more frequently demonstrated abnormalities of MSH2 and/or MSH6 (4/6, 67%) compared with MMRD colorectal carcinoma (23/149, 15%) (P=0.01). None of the MMRD small bowel adenocarcinomas harbored the BRAF V600E mutation, whereas 60% of MMRD colorectal carcinomas were positive for BRAF V600E with concurrent loss of MLH1 and PMS2 expression. Small bowel adenocarcinoma more frequently harbored Lynch syndrome-associated MMRD compared with colorectal carcinoma, providing support for screening of small bowel adenocarcinoma to identify patients at risk for Lynch syndrome. In contrast to colorectal carcinoma, sporadic MLH1 deficiency is not seen in small bowel adenocarcinoma. Clinicopathologic and histologic features do not distinguish between MMRP and MMRD small bowel adenocarcinoma indicating that universal screening in small bowel adenocarcinoma is necessary to detect patients at risk for Lynch syndrome.

MLH1-deficient Colorectal Carcinoma With Wild-type BRAF and MLH1 Promoter Hypermethylation Harbor KRAS Mutations and Arise From Conventional Adenomas.

Between 10% and 15% of colorectal carcinomas demonstrate sporadic DNA mismatch-repair protein deficiency as a result of MLH1 promoter methylation and are thought to arise from sessile serrated adenomas, termed the serrated neoplasia pathway. Although the presence of the BRAF V600E mutation is indicative of a sporadic cancer, up to 30% to 50% of colorectal carcinomas with MLH1 promoter hypermethylation will lack a BRAF mutation. We report the clinicopathologic and molecular features of MLH1-deficient colorectal carcinoma with wild-type BRAF and MLH1 promoter hypermethylation (referred to as MLH1-hypermethylated BRAF wild-type colorectal carcinoma, n=36) in comparison with MLH1-deficient BRAF-mutated colorectal carcinoma (n=113) and Lynch syndrome-associated colorectal carcinoma (n=36). KRAS mutations were identified in 31% of MLH1-hypermethylated BRAF wild-type colorectal carcinomas compared with 0% of MLH1-deficient BRAF-mutated colorectal carcinomas and 37% of Lynch syndrome-associated colorectal carcinomas. When a precursor polyp was identified, MLH1-hypermethylated BRAF wild-type colorectal carcinomas arose from precursor polyps resembling conventional tubular/tubulovillous adenomas in contrast to MLH1-deficient BRAF-mutated colorectal carcinomas, which arose from precursor sessile serrated adenomas (P<0.001). Both MLH1-hypermethylated BRAF wild-type colorectal carcinoma and MLH1-deficient BRAF-mutated colorectal carcinoma had a predilection for the right colon compared with Lynch syndrome-associated colorectal carcinoma (86% vs. 92% vs. 49%, P<0.001). There was no significant difference in mucinous differentiation, tumor-infiltrating lymphocytes, Crohn-like reaction, and medullary differentiation between the 3 tumor groups. Using Kaplan-Meier survival functions, there was no significant difference in disease-specific survival between the 3 patient groups (P>0.05). In conclusion, our results indicate that MLH1-hypermethylated BRAF wild-type colorectal carcinomas can harbor KRAS mutations and arise from precursor polyps resembling conventional tubular/tubulovillous adenomas.

A Practical Approach to the Evaluation of Gastrointestinal Tract Carcinomas for Lynch Syndrome.

Lynch syndrome accounts for roughly 1 of every 35 patients with colorectal carcinoma, making it the most common hereditary form of colorectal carcinoma. Identifying patients at risk for Lynch syndrome is essential, as these patients can develop additional Lynch syndrome-related tumors, and patients and their relatives benefit from genetic counseling. The hallmark of Lynch syndrome-associated neoplasms is DNA mismatch repair protein deficiency. In most instances, the pathologist is the first to identify patients at risk for Lynch syndrome and is tasked with communicating these results to treating clinicians and genetics counselors. This review will attempt to provide the tools for pathologists to identify patients at risk for Lynch syndrome through evaluation of tumors of the gastrointestinal tract and provide up-to-date knowledge on evaluating mismatch repair protein deficiency in tumors of the gastrointestinal tract.

Germline MLH1 Mutations Are Frequently Identified in Lynch Syndrome Patients With Colorectal and Endometrial Carcinoma Demonstrating Isolated Loss of PMS2 Immunohistochemical Expression.

Current guidelines on germline mutation testing for patients suspected of having Lynch syndrome are not entirely clear in patients with tumors demonstrating isolated loss of PMS2 immunohistochemical expression. We analyzed the clinical and pathologic features of patients with tumors demonstrating isolated loss of PMS2 expression in an attempt to (1) determine the frequency of germline MLH1 and PMS2 mutations and (2) correlate mismatch-repair protein immunohistochemistry and tumor histology with germline mutation results. A total of 3213 consecutive colorectal carcinomas and 215 consecutive endometrial carcinomas were prospectively analyzed for DNA mismatch-repair protein expression by immunohistochemistry. In total, 32 tumors from 31 patients demonstrated isolated loss of PMS2 immunohistochemical expression, including 16 colorectal carcinomas and 16 endometrial carcinomas. Microsatellite instability (MSI) polymerase chain reaction was performed in 29 tumors from 28 patients with the following results: 28 tumors demonstrated high-level MSI, and 1 tumor demonstrated low-level MSI. Twenty of 31 (65%) patients in the study group had tumors demonstrating histopathology associated with high-level MSI. Seventeen patients underwent germline mutation analysis with the following results: 24% with MLH1 mutations, 35% with PMS2 mutations, 12% with PMS2 variants of undetermined significance, and 29% with no mutations in either MLH1 or PMS2. Three of the 4 patients with MLH1 germline mutations had a mutation that results in decreased stability and quantity of the MLH1 protein that compromises the MLH1-PMS2 protein complex, helping to explain the presence of immunogenic but functionally inactive MLH1 protein within the tumor. The high frequency of MLH1 germline mutations identified in our study has important implications for testing strategies in patients suspected of having Lynch syndrome and indicates that patients with tumors demonstrating isolated loss of PMS2 expression without a germline PMS2 mutation must have MLH1 mutation analysis performed.

Isocitrate dehydrogenase-1 is mutated in inflammatory bowel disease-associated intestinal adenocarcinoma with low-grade tubuloglandular histology but not in sporadic intestinal adenocarcinoma.

The underlying molecular alterations in chronic idiopathic inflammatory bowel disease-associated intestinal adenocarcinoma remain largely unknown. Somatic IDH mutations are often seen in gliomas and myeloid leukemia but have also been recently reported in a subset of other neoplasms. We analyzed a series of intestinal adenocarcinomas with (n=23) and without (n=39) associated chronic idiopathic inflammatory bowel disease treated at our institution for IDH1 and IDH2 mutations and correlated the clinicopathologic findings with mutation status. Compared with intestinal adenocarcinomas not associated with inflammatory bowel disease, adenocarcinomas associated with inflammatory bowel disease more frequently demonstrated IDH mutations (13% vs. 0%, P=0.047). All IDH mutations were identified in IDH1 and resulted in substitution of arginine by cysteine at position 132 (p.R132C, c.394C>T). IDH1 mutations were frequently (66%) associated with concurrent KRAS mutations (p.G12D, c.35G>A). IDH1-mutated intestinal adenocarcinomas were seen in the setting of both Crohn disease and ulcerative colitis and were located in both the ileum and colon. Compared with IDH1-negative inflammatory bowel disease-associated adenocarcinoma, IDH1-positive adenocarcinomas more frequently demonstrated tubuloglandular histology (100% vs. 25%, P=0.032) and were more frequently associated with precursor lesions exhibiting serrated morphology (66% vs. 6%, P=0.034). IDH1 mutations were also identified in the precursor dysplastic lesions associated with IDH1-positive adenocarcinomas. In conclusion, we demonstrate that IDH1 mutations are occasionally identified in inflammatory bowel disease-associated intestinal adenocarcinoma but not in intestinal adenocarcinoma not associated with inflammatory bowel disease. In addition, IDH1-mutated intestinal adenocarcinoma is associated with a characteristic low-grade tubuloglandular histology and often harbors concurrent KRAS mutations. Identification of patients with IDH1-mutated intestinal adenocarcinoma may become clinically important as new therapies emerge that target tumors that harbor IDH mutations.

GNAS is frequently mutated in both low-grade and high-grade disseminated appendiceal mucinous neoplasms but does not affect survival.

We analyzed a series of 55 disseminated appendiceal mucinous neoplasms treated at our institution for GNAS and KRAS mutations in an attempt to correlate mutation status with clinicopathological findings and patient survival. GNAS mutations (p.R201H, c.602G>A and p.R201C, and c.602C>T) were identified in 17 (31%) of 55 of disseminated mucinous neoplasms and were found in 8 (35%) of 23 low-grade mucinous neoplasms, 7 (37%) of 19 high-grade mucinous adenocarcinomas lacking a signet ring cell component, and 2 (15%) of 13 high-grade mucinous adenocarcinomas with a signet ring cell component. All 7 mucinous adenocarcinomas composed of pure (>95%) signet ring cells harbored wild-type GNAS. There was no significant association between GNAS mutations and sex and age (both with P > .05) or between GNAS mutations and individual adverse histologic features including cytologic grade, destructive invasion, tumor cellularity, angiolymphatic invasion, perineural invasion, and signet ring cells (all with P > .05). KRAS mutations were identified in 22 (40%) of 55 disseminated mucinous neoplasms. GNAS-mutated disseminated appendiceal mucinous neoplasms more frequently harbored concurrent KRAS mutations compared with GNAS wild-type tumors (65% versus 29%, P = .018). GNAS mutations were not significantly associated with overall survival (both with P > .05). Only overall tumor grade was an independent predictor of overall survival in the multivariate analysis (P = .01). Our results indicate that GNAS mutations are frequently identified in both low-grade and high-grade disseminated appendiceal mucinous neoplasms indicating that GNAS mutation status cannot be used to distinguish between low-grade from high-grade appendiceal mucinous neoplasms.

BRAF-mutated microsatellite stable colorectal carcinoma: an aggressive adenocarcinoma with reduced CDX2 and increased cytokeratin 7 immunohistochemical expression.

Reduced CDX2 and cytokeratin 20 (CK20) expression in colorectal carcinoma with BRAF mutation and high-level microsatellite instability (MSI-H) has been well documented. The immunophenotype of BRAF-mutated microsatellite stable (MSS) colorectal carcinoma has not been reported. We analyzed 205 colorectal carcinomas including 28 BRAF-mutated MSS, 53 BRAF-mutated MSI-H, and 124 BRAF wild-type MSS tumors for CDX2, cytokeratin 7 (CK7), and CK20 immunohistochemical expression. CDX2 was scored semiquantitatively for both staining intensity and percent of tumor cells staining and a modified CDX2 H-score was calculated. Patients with BRAF-mutated MSS colorectal carcinomas were more frequently stage IV at presentation compared to patients with BRAF-mutated MSI-H colorectal carcinomas and BRAF wild-type MSS colorectal carcinomas (32% versus 8% versus 15%, P < .001). BRAF-mutated MSS colorectal carcinoma displayed reduced CDX2 expression compared to BRAF wild-type MSS colorectal carcinoma (75% versus 94%; mean CDX2 H-score 98 versus 150, P < .001). CK7 expression was more often identified in BRAF-mutated MSS colorectal carcinoma compared to both BRAF-mutated MSI-H colorectal carcinoma and BRAF wild-type MSS colorectal carcinoma (39% versus 6% versus 6%, P = .0001). BRAF-mutated MSI-H colorectal carcinomas were less often CK20 positive compared to BRAF-mutated MSS and BRAF wild-type MSS tumors (70% versus 93% versus 90%, P = 0.001). In summary, BRAF-mutated MSS colorectal carcinoma often displays reduced CDX2 and increased CK7 expression. Knowledge of this altered immunophenotype is important as patients with BRAF-mutated MSS colorectal carcinoma often present with metastatic disease and the altered tumor immunophenotype may lead to the erroneous assumption that origin from the colon/rectum is unlikely.

Loss of SMAD4 protein expression is associated with high tumor grade and poor prognosis in disseminated appendiceal mucinous neoplasms.

The distinction between low-grade and high-grade disseminated appendiceal mucinous neoplasms is of critical importance in assessing prognosis and guiding patient therapy. SMAD4 encodes a protein that is a central component of the TGFß signal transduction pathway, and loss of SMAD4 expression has been associated with poor prognosis in carcinomas of the gastrointestinal tract. We reviewed the clinicopathologic and molecular features of 109 disseminated appendiceal mucinous neoplasms identified over an 8-year period at our institution in an attempt to: (1) correlate SMAD4 immunohistochemical expression with tumor grade; and (2) assess the prognostic significance of SMAD4 expression in predicting overall survival. Compared with tumors demonstrating preserved SMAD4 expression, tumors with loss of SMAD4 expression more frequently exhibited high cytologic grade (85% vs. 50%, P=0.035), high cellularity (100% vs. 45%, P<0.001), and destructive invasion (100% vs. 55%, P=0.001). SMAD4 expression significantly correlated with overall tumor grade (P=0.003): all 13 tumors with loss of SMAD4 expression were high grade, whereas all 42 low-grade tumors displayed preserved SMAD4 expression. A significantly higher proportion of tumors with loss of SMAD4 immunohistochemical expression demonstrated loss of heterozygosity at chromosome 18q (38%) compared with tumors with preserved SMAD4 expression (11%) (P=0.049), suggesting that loss of SMAD4 expression is due to genomic deletion in a high proportion of cases. Patients with SMAD4-negative tumors had significantly worse overall survival in comparison with patients with preserved SMAD4 expression (log rank P=0.023). However, our multivariable analysis found that SMAD4 expression was not independent of overall tumor grade in predicting overall survival. Our results indicate that loss of SMAD4 immunohistochemical expression is associated with loss of heterozygosity at chromosome 18q and is always associated with aggressive histologic features in disseminated appendiceal mucinous neoplasms. SMAD4 immunohistochemistry may be a useful ancillary study in select cases of disseminated appendiceal neoplasia, in which the distinction between low-grade and high-grade tumors is difficult.

The histopathology of PRSS1 hereditary pancreatitis.

Hereditary pancreatitis is an autosomal dominant disorder with 80% penetrance and variable expressivity. The vast majority of cases have been linked to mutations within the cationic trypsinogen gene, also referred to as serine protease 1 (PRSS1). Other than inheritance, PRSS1 pancreatitis has been considered clinically and pathologically indistinguishable from other etiologies of chronic pancreatitis. However, to date, the histologic findings of PRSS1 pancreatitis have not been well described. We, therefore, collected pancreatic specimens from 10 PRSS1 patients of various ages and examined their clinicopathologic features. Patients at the time of resection ranged in age from 9 to 66 years (median, 29 y), with a slight female predominance (60%). All patients reported a history of intermittent abdominal pain, with an age of onset ranging from infancy to 21 years of age. Examination of the gross and microscopic findings suggested a sequential pattern of changes with increasing patient age. In pediatric patients (n=4), although in most cases the pancreas was grossly normal, there was microscopic variation in lobular size and shape. Although the central portions of the pancreas displayed parenchymal loss accompanied by loose perilobular and interlobular fibrosis, the periphery was remarkable for replacement by mature adipose tissue. These changes were more developed in younger adults (n=2), in whom fatty replacement seemed to extend from the periphery to the central portions of the pancreas. With older patients (n=4), the pancreas showed marked atrophy and extensive replacement by mature adipose tissue with scattered islets of Langerhans and rare acinar epithelium concentrated near the main pancreatic duct. In summary, PRSS1 hereditary pancreatitis is characterized by progressive lipomatous atrophy of the pancreas.