An overview of practical issues in the diagnosis of gastroenteropancreatic neuroendocrine pathology

CONTEXT

Although somewhat uncommon, neuroendocrine tumors of the gastrointestinal tract and pancreas have come under scrutiny in recent times. With advances in imaging techniques, more of these tumors are being removed and sent for pathologic evaluation. It is important for the diagnostic pathologist to be aware of recent developments in this field.

OBJECTIVE

This overview focuses on nomenclature/terminology, classification, practical issues related to recent developments in immunohistochemical markers that aid diagnosis and may relate to prognosis, and molecular advances.

DATA SOURCES

Currently available literature and personal experience in the field of neuroendocrine pathology.

CONCLUSIONS

The preferred terminology is neuroendocrine/tumor/carcinoma and it is recommended that the World Health Organization classification be used, taking note of the site variations that may occur. A large number of immunohistochemical markers are available but a core panel that is relevant to the site should be used. Cytokeratin 19 positivity is an independent marker of aggressive behavior in pancreatic neuroendocrine tumors. Gastrointestinal neuroendocrine tumors arise via the CpG island methylator phenotype pathway, whereas their pancreatic counterparts arise as a result of chromosomal instability. The MEN1 gene is implicated in both syndromic and sporadic forms of these tumors.

Revision 2: an immunohistochemical approach and evaluation of solid pseudopapillary tumour of the pancreas

Solid pseudopapillary tumours (SPT) of the pancreas are uncommon, but with widespread and increased imaging, several of these lesions are coming to light incidentally and are subject to needle biopsies. On limited material and especially the solid or clear cell, variants of SPT can morphologically mimic most notably pancreatic neuroendocrine tumours and even metastatic renal cell carcinoma or melanoma. In this context, immunohistochemistry is important and useful in helping to reach the correct diagnosis. Several antibodies have been used in the immunohistochemical evaluation of SPT. As with most tumours, no one marker is specific, but rather a core panel is advocated. Recently, both beta-catenin and E-cadherin have been shown to be of value in SPT. Nuclear and cytoplasmic decoration of tumour cells by beta-catenin is seen in almost 100% of cases. This protein relocalisation away from the cell membrane is underscored by mutations of the beta-catenin gene. Mutations of the CDH1 gene are very uncommon in SPT, but the immunohistochemically detected changes to the protein are consistent and present in 100% of cases. Using an E-cadherin antibody to the extracellular domain of the molecule results in complete membrane loss, while the antibody directed to the cytoplasmic fragment produces distinct nuclear staining of the tumour cells. In addition, there is concordance of staining abnormalities between the two antibodies. When combined with CD10 and progesterone receptor positivity, a diagnosis of SPT can be rendered with confidence even in small biopsy samples.

MRI total sagittal abdominal diameter as a predictor of metabolic syndrome compared to visceral fat at L4-L5 level

OBJECTIVE

To compare associations between anteroposterior (AP) diameter or sagittal abdominal diameter - a measure of total central fat, and visceral fat alone with the metabolic syndrome as defined by ATPIII criteria.

RESEARCH DESIGN AND METHODS

Twenty-four Caucasian male with type 2 diabetes and 24 non-diabetic Caucasian male subjects [body mass index (BMI) (+/-SD): 32.23 +/- 7.52 kg/m(2), age (+/-SD): 51.35 +/- 13.80 years] were studied by magnetic resonance imaging (MRI) scan to measure central fat at L4-L5 level. The visceral and total central adipose tissue was calculated in cm(2) and total sagittal MRI diameter and visceral sagittal MRI diameters in cm. Components of the ATPIII definition of the metabolic syndrome and circulating adipocytokine concentrations were also measured.

RESULTS

MRI total sagittal abdominal diameter was positively associated with waist circumference in controls (r=0.62, p=0.007) and in diabetic subjects (r=0.81, p<0.001). Binary logistic regression analysis showed that MRI-calculated total sagittal diameter (r=0.61, p=0.002) was a more significant predictor of the adverse metabolic profile of the metabolic syndrome than MRI-assessed visceral fat. Receiver operating characteristic curves revealed that MRI-calculated total sagittal diameter most effectively identified subjects with the metabolic syndrome.

CONCLUSIONS

MRI-calculated total sagittal abdominal diameter is a non-validated MRI method that predicts the adverse metabolic profile of the ATPIII definition of the metabolic syndrome. Antero-posterior fat is a dimension of central fat that seems to be more closely associated with cardiovascular risk compared to visceral fat.

p120 catenin reduction and cytoplasmic relocalization leads to dysregulation of E-cadherin in solid pseudopapillary tumors of the pancreas

Solid pseudopapillary tumors (SPTs) of the pancreas have characteristic morphologic features and show consistent beta-catenin abnormalities and loss of E-cadherin protein. The loss of cell-to-cell adhesion is thought to contribute to frequent cystic degeneration and pseudopapillae formation. p120 regulates E-cadherin and is responsible for its degradation.A tissue microarray of 20 cases and whole sections from another 9 cases of SPT were stained with p120, beta-catenin, and E-cadherin. All 29 cases showed cytoplasmic and nuclear staining for beta-catenin, loss of E-cadherin, and decrease or loss of p120 membrane localization but cytoplasmic staining instead. Loss of membrane p120 staining with relocalization to the cytoplasm was seen in cystic and solid areas of the tumors. This study indicates that p120 expression in SPTs is abnormal and loss of E-cadherin is probably consequent on p120 loss or decrease. Aberrations and other alterations of the E-cadherin gene are unlikely to be responsible for the loss of E-cadherin in SPTs.

Gastrointestinal stromal tumor with autonomic nerve differentiation and coexistent mantle cell lymphoma involving the appendix

Gastrointestinal stromal tumor (GIST) and mantle cell lymphoma involving the appendix are rare as individual disease entities. Their coexistence has not been previously reported in the literature. We describe a 65-year old female who presented with extensive ileocecal mantle cell lymphoma, which extended to the appendix. The appendix was involved by mantle cell lymphoma and an incidental coexistent GIST was noted in the appendiceal wall. The GIST was CD117 positive but did not harbor mutations in the c-kit and PDGFR genes. In addition, it was unusual in showing S-100 immunoreactivity and ultrastructural evidence of autonomic nerve differentiation. This is the first description of the association of a GIST with autonomic nerve differentiation coexisting with mantle cell lymphoma in the appendix.

Epstein-Barr virus-associated lymphoepithelioma-like gastric carcinoma

This article provides an overview of the pathology of Epstein-Barr virus (EBV)-associated lymphoepithelioma-like gastric carcinoma, highlighting its unique morphology and clinical features. Lymphoepithelioma-like gastric carcinoma is a rare neoplasm of the stomach with a better prognosis than conventional adenocarcinoma. Most lymphoepithelioma-like gastric carcinomas are associated with EBV infection, while a subset is associated with microsatellite instability. Even though there is a very strong association with EBV, its exact role in carcinogenesis still remains to be elucidated in those cancers that harbor EBV. Distinctive histology and demonstration of EBV using in situ hybridization, polymerase chain reaction, or Southern blotting and immunohistochemistry for the DNA mismatch repair genes or polymerase chain reaction analysis of microsatellite loci to assess microsatellite instability helps to make the diagnosis.

Small and microscopically detected gastrointestinal stromal tumours: an overview

Small or microscopic gastrointestinal stromal tumours (GISTs) have been the focus of recent publications. These lesions may accompany clinically overt GISTs or be found incidentally in resection specimens for gastro-oesophageal malignancies. While the majority of cases consist of single lesions, approximately 30% may be multiple (usually two or three such lesions). Several appellations have been employed to describe these small GISTs: minute GISTs, GIST tumourlets, interstitial cell of Cajal (ICC) hyperplasia, microscopic GISTs, minimal GISTs, and sclerosing stromal tumourlets. As such, there has been no uniformity in terms of the size of these small or microscopic lesions with tumours as small as 0.2 mm and those up to 10 mm, all falling within the remit of microscopic or minute GISTs. These lesions have a predilection for the gastro-oesophageal junction and occur slightly more frequently in the proximal stomach. They are typified by spindle-shaped cells set within a hyalinised stroma which also shows calcification. Even the smallest lesion has been shown to harbour mutations of the c-kit gene. They are biologically indolent, and the majority of lesions appear to remain small and/or show evidence of involution. However, it is possible that some are the precursors of clinically significant GISTs.

Membrane loss and aberrant nuclear localization of E-cadherin are consistent features of solid pseudopapillary tumour of the pancreas. An immunohistochemical study using two antibodies recognizing different domains of the E-cadherin molecule

AIM

To examine the expression of E-cadherin in solid pseudopapillary tumours (SPT) of the pancreas using two monoclonal antibodies recognizing two different domains of the E-cadherin molecule.

METHODS AND RESULTS

Twenty cases of SPT were collected and a tissue microarray (TMA) constructed. The TMA was stained with commercially available antibodies to E-cadherin and beta-catenin. All 20 cases displayed nuclear beta-catenin as well as aberrant E-cadherin expression. With the antibody that stains the cytoplasmic domain of E-cadherin (clone 36, BD Transduction Laboratories), all 20 cases demonstrated nuclear E-cadherin reactivity, whereas with use of the antibody that recognizes the extracellular domain (clone 36B5, Vector Laboratories), no reactivity was observed in any of the cases.

CONCLUSION

This study shows that aberrant beta-catenin and E-cadherin protein expression occurs in 100% of SPT, is probably linked mechanistically to beta-catenin nuclear localization, and two distinct patterns of E-cadherin immunoreactivity are seen in SPT: nuclear (with the antibody against the cytoplasmic domain), or immunonegativity (complete loss) when stained with the antibody for the E-cadherin extracellular fragment.

Frequent accumulation of nuclear E-cadherin and alterations in the Wnt signaling pathway in esophageal squamous cell carcinomas

Esophageal squamous cell carcinoma is frequently associated with poor prognosis, as a result of high levels of lymph node metastasis. So far, very few genetic abnormalities have been associated with this disease, and its molecular etiology remains largely unknown. To assess whether the Wnt pathway contributes to esophageal squamous cell carcinoma, we characterized the expression and subcellular localization of the key Wnt signaling components in all 30 cases of esophageal squamous cell carcinomas analyzed. We found abnormal expression and/or localization in glycogen synthase kinase-3 alpha/beta (34%), Axin2 (48%), alpha-catenin (31%), MYC (73%) and cyclin D1 in 46% of cases. Only 13% of tumors showed nuclear accumulation of beta-catenin. By contrast, 60% showed nuclear expression of E-cadherin using an antibody that recognizes the cytoplasmic domain of E-cadherin. When the same tumors were stained with antibody raised against the extracellular domain of E-cadherin, the expression was lost. A direct correlation was found between nuclear E-cadherin and the increased nuclear cyclin D1, one of the AP-1 target genes in these tumors. By transfection experiments, the cytoplasmic portion of E-cadherin was found to activate the AP-1 transcription factor pathway and induced cyclin D1 promoter activity, but beta-catenin/Tcf transcription activity was unaffected. Nuclear expression of E-cadherin was also detected in tumors other than squamous cell carcinoma, including pancreatic and colon cancers, albeit at lower frequency. Nuclear accumulation of a portion of E-cadherin in esophageal squamous cell carcinoma and the other types of tumors indicates that, in addition to the previously implicated tumor suppressor activity of E-cadherin, modified forms of this glycoprotein might also play a role in growth promotion.

The clinical significance of massive intratumoral lymphocytosis in squamous cell carcinoma of the anus

A recent report indicates that patients with squamous cell carcinoma of the anal canal (SCCAC) and intraepithelial lymphocytes have a poor prognosis. Against that background, histological sections from 277 consecutive SCCACs were reviewed searching for cases with massive tumor-infiltrating lymphocytes (TILs; >/= 50 lymphocytes /100 tumor cells). Of the 277 SCCACs, 8 (3%) had massive TILs. These 8 patients (all females) had both more advanced clinical stage than the remaining 269 control SCCAC patients. Follow-up studies revealed that the 8 patients with SCCACs having massive TILs had a much better 15 years survival rate than control SCCAC patients. It is concluded that despite SCCAC patients with massive TILs had a more advanced clinical stage than SCCAC controls, SCCAC with massive TILs patients had a longer survival rate (with no deaths after 5 years) than control cases. The search via proteomic methodology for the lymphocyte-attracting tumor protein might bring forward a novel co-adjuvant therapy, capable to increase prolonged survival time in patients having SCCAC without massive TILs.

Predicting prognosis in gastroentero-pancreatic neuroendocrine tumors: an overview and the value of Ki-67 immunostaining

Gastroenteropancreatic neuroendocrine tumors (GEP-NETS) are unusual and rare neoplasms for which prognostic assessment and the diagnosis of malignancy, on the basis of histology alone, represent considerable challenges for the pathologist. To date, many molecular markers have been identified with a view to providing accurate and timely prediction of response to treatment and long-term survival. Proliferation remains a key feature of tumor progression, which has been widely estimated by the immunohistochemical use of the Ki-67 nuclear antigen. Given the continued difficulties inherent in prediction of malignancy in pancreatic neuroendocrine tumors (PETs) in particular, it has become unclear whether Ki-67 is truly a reliable prognostication marker. This review seeks to better establish what the consensus is on the role of the Ki-67 proliferation index as a prognostic indicator of long-term outcome in pancreatic neuroendocrine tumors. We conclude that most studies favor the utility of the Ki-67 proliferation index despite different critical percentages and in concert with other pathological parameters in the routine work-up of PETs.

Clear cell (glycogen rich) gastric adenocarcinoma: a distinct tubulo-papillary variant with a predilection for the cardia/gastro-oesophageal region

AIMS

To explore the clinicopathological and immunohistochemical profile of clear cell gastric cancers with a tubulo-papillary pattern.

METHODS

Twelve cases of clear cell gastric cancer (containing a minimum of 10% of clear cells) were studied. The cases were stained with: CK7, CK20, CEA, AFP, cyclin D1, E-cadherin and CDX-2.

RESULTS

There were nine males and three females with an age range of 62 to 82 years (mean 71.4 years). Ten cases were located in the gastric cardia with extension into the gastro-oesophageal junction and two were in the pylorus/pre-pyloric area. Tumours ranged from 2 to 9 cm (mean 4.5 cm), nine were polypoid, exophytic grossly and all had a tubulo-papillary histological pattern. Five cases contained intracytoplasmic hyaline globules. Lymph node involvement was present in eight cases. Eight cases were CK7 positive, four were CK20 positive and all 12 were CEA, cyclin D1, E-cadherin and CDX-2 positive. All cases were AFP negative. Five patients had recurrence and/or metastasis within 6 months.

CONCLUSION

Clear cell gastric cancers have a predilection for the gastro-oesophageal junction, are polypoid, have a tubulopapillary pattern, and show over-expression of cyclin D1 but normal E-cadherin.

Oncocytic papillary neoplasms of the biliary tract: a clinicopathological, mucin core and Wnt pathway protein analysis of four cases

AIMS

Oncocytic change in papillary neoplasms of the biliary tract is a very uncommon finding with little known about pathogenesis, immunophenotype and prognosis, especially in comparison to similar lesions in the pancreatic ductal system. We report four cases of oncocytic biliary intraductal papillary neoplasms (IPNs), highlighting the clinicopathological characteristics of these tumours, the immunohistochemical profile with regard to Wnt pathway proteins and mucin core protein (MUC) status, and compare these findings with the oncocytic variant of intraductal papillary mucinous neoplasm (IPMN) of the pancreas.

METHODS

Four cases of oncocytic IPN of the extrapancreatic, biliary tree (two with accompanying invasive carcinomas) were examined for mucin profiles and Wnt signalling proteins. The cases were stained for: beta-catenin, c-myc, glutathione synthase kinase (GSK), E-cadherin, cyclin D1, and adenomatous polyposis coli (APC), and MUC1, MUC2, MUC3, MUC4, MUC5AC, MUC5B and MUC6, using standard immunohistochemistry.

RESULTS

The cases occurred in three males and one female, ranging in age from 59 to 81 years. The lesions caused obstructive symptoms related to the biliary tree as well as non-specific abdominal symptoms. Typically, cystic lesions were noted grossly. All four of the IPNs were composed of distinctive oncocytic cells. The invasive carcinomas accompanying two of the cases were also composed of oncocytes. None of the cases showed aberrant expression of the Wnt signalling proteins, although cyclin D1 was markedly over-expressed in all four cases. Three of four cases showed the following mucin profile: MUC3, MUC4, MUC5AC, MUC5B and MUC6 positive.

CONCLUSIONS

The Wnt pathway proteins (especially beta-catenin and E-cadherin) are expressed normally in oncocytic variants of intraductal papillary neoplasms of the biliary tree, and the mucin profile is similar to their counterparts in the pancreas.

Psammomatous melanotic schwannoma presenting as colonic polyps

Psammomatous melanotic schwannoma is an uncommon neoplasm that usually occurs in the setting of Carney's complex. They can occur in the gastrointestinal tract with preferential location in the stomach. A 43-year-old female presented with two colonic polyps at routine endoscopy. The patient was asymptomatic and did not have features of Carney's complex. Both polyps were composed of melanin-containing epithelioid and spindle cells with several psammoma bodies. There was no evidence of cytological atypia or necrosis. The tumor was diffusely positive for S-100, and focally for HMB-45 and melan-A. The differential diagnosis includes melanoma, GIST, pigmented neuroendocrine tumor, and epithelioid leiomyoma. The lack of malignant features separates this lesion from melanoma while the immunophenotype of the other lesions is characteristic.

Adenosquamous carcinoma of the pancreas with clear cell and rhabdoid components. A case report

CONTEXT

In as much as no such variant of this pancreatic tumour has been previously reported in the literature, we report an unusual case of an adenosquamous carcinoma of the pancreas characterized by clear cells and rhabdoid cells.

CASE REPORT

A 75-year-old man presented with upper abdominal distention, dyspepsia, jaundice, and significant weight loss over a period of 3 months. Imaging of the abdomen showed a solid mass with cystic components in the region of the uncinate process of the pancreas. Endoscopic retrograde pancreatography showed mild to moderate dilatation of the intrapancreatic biliary tract and of the pancreatic duct, and a biliary stent was placed. The patient subsequently underwent a Whipple's procedure with curative intent. Histological evaluation of the pancreatic mass revealed an adenosquamous carcinoma displaying both clear cell and rhabdoid components.

CONCLUSIONS

Assessing the predominant histology of pancreatic adenosquamous carcinoma variants such as those characterized by clear cells and rhabdoid cells may help select and improve upon therapies in this aggressive lesion.

Nuclear expression of E-cadherin in solid pseudopapillary tumors of the pancreas

CONTEXT

Solid pseudopapillary tumors of the pancreas are rare and have recently been shown to harbor mutations of the beta-catenin gene with resultant nuclear localization of beta-catenin protein to the nucleus. Moreover, there is a close relationship between beta-catenin and E-cadherin.

OBJECTIVE

To explore the protein expression of E-cadherin in a series of solid pseudopapillary tumors of the pancreas.

PARTICIPANTS

Eighteen cases of solid pseudopapillary tumors of the pancreas.

DESIGN

The cases were studied using a tissue microarray that was constructed as follows: for each case, 4 to 14 cores measuring 1.0 mm each were drilled from the blocks. Tissue cores from normal pancreas were used as controls and for orientation purposes.

MAIN OUTCOME MEASURES

The slides were stained with the following commercially available antibodies: CD10, CD56, vimentin, alpha-1-antitrypsin, alpha-1-antichymotrypsin, neuron-specific enolase, chromogranin, synaptophysin, beta-catenin and E-cadherin.

RESULTS

All the tumors were CD10, vimentin, alpha-1-antitrypsin and alpha-1-antichymotrypsin diffusely positive (50% or more of the tumor cells staining) and CD56 showed focal positivity in all cases with 5-10% of tumor cells displaying immunolabeling. All cases were negative for chromogranin and synaptophysin. All 18 cases displayed cytoplasmic and nuclear localization of beta-catenin protein. Similarly, E-cadherin protein was localized to the nucleus in all 18 cases, with loss of the characteristic membranous decoration of cells.

CONCLUSION

This study is the first demonstration of aberrant nuclear localization of E-cadherin protein in solid pseudopapillary tumors of the pancreas. Whilst the exact mechanism is not know and nuclear E-cadherin is not related to tumor aggression, this staining pattern may be of diagnostic value in concert with beta-catenin staining.

Primary paratesticular osteosarcoma: case report and a review of the literature

Primary paratesticular osteosarcoma is an extremely rare malignancy and, to date, only a few cases have been reported. To our knowledge, no such case arising directly from paratesticular soft tissue has been described. We describe a 52-year-old man who presented with left scrotal swelling and an excisional biopsy that revealed a sarcomatous lesion. Left inguinal orchiectomy was performed and histologic examination of the extensively sampled lesion revealed a pure paratesticular osteosarcoma. The patient died 6 months after the diagnosis with disseminated disease.

Squamous cell carcinoma with rhabdoid phenotype and osteoclast-like giant cells in a renal-pancreas transplant recipient

Squamous cell carcinoma (SCC) is the commonest non-melanotic malignant skin tumour encountered after solid-organ transplantation. In this setting it is associated with a worse prognosis than sun-damage-induced SCC. Rhabdoid cells and osteoclastic giant cells are infrequently seen in SCC. This case highlights the unusual occurrence of rhabdoid cells and osteoclastic giant cells in a post-transplant SCC.