Primary Mixed Adenocarcinoma and Small Cell Carcinoma of the Appendix

Appendiceal collision tumors: case reports, management and literature review

Appendiceal tumors are incidentally detected in 0.5% cases of appendectomy for acute appendicitis and occur in approximately 1% of all appendectomies. Here, we report two cases of appendiceal collision tumors in two asymptomatic women. In both cases, imaging revealed right-lower-quadrant abdominal masses, which were laparoscopically resected. In both cases, histological examinations revealed an appendiceal collision tumor comprising a low-grade appendiceal mucinous neoplasm and well-differentiated neuroendocrine neoplasm (NEN). For complete oncological control, right hemicolectomy was performed in one patient for the aggressive behavior of NEN; however, histology revealed no metastasis. The other patient only underwent appendectomy. No further treatment was recommended. According to the latest guidelines, exact pathology needs to be defined. Proper management indicated by a multidisciplinary team is fundamental.

Ipilimumab and nivolumab for recurrent neuroendocrine cervical carcinoma

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Neuroendocrine carcinoma of the cervix is a rare and aggressive HPV-mediated malignancy with a high recurrence rate.

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Combination ipilimumab and nivolumab has been shown to effect disease response in pulmonary neuroendocrine carcinoma.

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We present three patients with recurrent neuroendocrine cervical carcinoma who experienced response to ipilimumab/nivolumab.

Neuroendocrine carcinoma of the cervix is a rare subtype of cervical cancer with a poor prognosis. Primary treatment of this disease involves a combination of surgery, chemotherapy, and radiation. The majority of patients will experience disease recurrence, for which there exist no treatment guidelines. Because of histologic similarities, small cell lung cancer has often informed management of extrapulmonary neuroendocrine carcinomas. Immunotherapy regimens, including a combination of ipilimumab and nivolumab, have been shown to have activity in small cell lung cancer. In this report, we present the cases of 3 patients with recurrent neuroendocrine carcinoma of the cervix who experienced durable response to a combination of ipilimumab and nivolumab.

Primary Small Cell Carcinoma of the Kidney: Disease Characteristics and Treatment Outcomes

Background: Primary small cell carcinoma of the kidney (PSCCK) is exceedingly rare and data on disease characteristics and outcomes are sparse. This study examines a nationally-representative cancer registry to better characterize PSCCK. Methods: We queried the National Cancer Database to identify patients with histology-confirmed PSCCK from 2004 to 2015. Adjusted Cox proportional hazards regression and Kaplan–Meier analyses were employed to assess predictors of mortality and estimate median survival time, respectively. Results: A total of 110 patients were included (47:53% female:male, 77% ≥60 years of age, 86% Caucasian). Significant predictors of mortality included female sex, age 60–69 years, treatment at an Integrated Network Cancer Program, stage cM1, and lack of surgical and chemoradiotherapy treatment. Independent protective factors were high socioeconomic status and treatment at an Academic Research Program. The estimated median overall survival time was 9.31 (95% CI 7.28–10.98) months for all patients. No differences in estimated survival time were observed across individual treatment modalities among those patients who underwent treatment (p = 0.214). Conclusions: PSCCK is an aggressive malignancy with a median survival time of less than one year. Future studies that correlate clinical tumor staging with specific treatment modalities are needed to optimize and individualize management.

Management and outcome of an appendiceal collision tumour composed of neuroendocrine and mucinous neoplasms

We report an appendiceal collision tumour in a 23-year-old woman who presented with constipation and abdominal fullness. Imaging revealed a right lower quadrant abdominal mass that was laparoscopically resected. Histology revealed an appendiceal collision tumour composed of a low-grade mucinous neoplasm and well-differentiated neuroendocrine neoplasm. A right hemicolectomy for complete oncological control was performed revealing metastatic spread of the neuroendocrine component to the lymph nodes. No further treatment was recommended and the patient was followed with expectant management. At 2-year follow-up, no evidence of disease was found on surveillance imaging. Appendiceal collision tumours can arise in young adults; treatment should be guided by oncological principles of the component tumours.

Primary mixed adenocarcinoma and small-cell carcinoma of appendix: A case report (CARE-compliant)

RATIONALE

Primary extrapulmonary small-cell carcinoma (SCC) of appendix is reported very rarely. We report herein a case of mixed SCC and adenocarcinoma of appendix.

PATIENT'S CONCERN

A 70-year-old female was consulted to our Emergency Department with the right lower abdominal pain and low-grade fever for 2 days.

DIAGNOSIS

Abdominal ultrasonography revealed the perforated appendicitis with periappendiceal abscess. Postoperative histology confirmed the diagnosis of mixed SCC and adenocarcinoma.

INTERVENTIONS

After laparoscopic appendectomy, she underwent right hemicolectomy for radical surgery.

OUTCOMES

Laparoscopic appendectomy was performed and histological examination showed mixed SCC and adenocarcinoma. After confirming that there was no other organ metastasis, right hemicolectomy was performed for radical surgery. Five months after surgery, the patient expired due to multiple organ metastases.

LESSONS

Further studies are required for better understanding of disease entities, and clinical trials are needed to define adequate treatment strategies for extrapulmonary SCC.

Whole-Exome Sequencing of Sinonasal Small Cell Carcinoma Arising within a Papillary Schneiderian Carcinoma In Situ

OBJECTIVE

The pathogenetic underpinnings of extrapulmonary small cell carcinomas (EPSCCs) of the head and neck are poorly understood. We sought to describe the clinical case and whole-exome DNA sequencing data of a patient with sinonasal Schneiderian carcinoma in situ whose tumor progressed to small cell carcinoma (SCC).

STUDY DESIGN

Case report and whole-exome sequencing of tumor DNA.

SETTING

Academic medical center.

SUBJECTS AND METHODS

A 52-year-old man with sinonasal Schneiderian carcinoma in situ whose tumor progressed to small cell carcinoma. We performed whole-exome genetic sequencing and copy-number variation (CNV) analysis of tumor and normal DNA extracted from flash-frozen, paraffin-embedded (FFPE) samples.

RESULTS

A total of 93 high-confidence, nonsynonymous somatic mutation events were identified in sinonasal SCC, including loss-of-function mutations in TP53, MAML3, a transcriptional coactivator of the Notch pathway, and GAS6, an activating ligand of the TAM family of tyrosine kinase receptors. Focal amplifications of chromosomal regions 6p25-11.1, containing SOX4 and VEGFA, and 14q32.1-32.3, containing AKT1 and the Notch inhibitory ligand DLK1, were also seen. Further CNV analysis revealed deletions in the critical cell cycle regulators CDKN2A, RB1, RBL1, and RBL2 and the chromatin modifier EP300.

CONCLUSIONS

Small cell carcinoma may rarely arise from sinonasal Schneiderian carcinoma in situ and exhibits similar genomic aberrations (eg, SOX amplification, Notch pathway inactivation) to pulmonary small cell carcinoma.

Two rare cases of appendiceal collision tumours involving an appendiceal mucinous neoplasm and carcinoid

We report two rare cases of appendiceal collision tumours, each involving an appendiceal mucinous neoplasm with a concomitant appendiceal carcinoid. The first case presented with acute appendicitis while the second presented with an incidental radiological finding of an enlarged appendix as part of evaluation for raised serum carcinoembryonic antigen. Diagnosis in both cases was made postoperatively on histological assessment following appendicectomy. Clinical and histological features of both tumour types in each case did not necessitate further surgical resection or adjuvant treatment. Both patients did well postoperatively and had no evidence of disease recurrence on follow-up.

Distinct genetic alterations in small cell carcinoma from different anatomic sites

Small cell carcinoma (SmCC) is a distinct clinicopathological entity first described in the lung. It represents approximately 15% of all bronchogenic carcinoma. Extrapulmonary small cell carcinoma (EPSmCC) morphologically indistinguishable from small cell lung cancer (SCLC) was first reported in 1930. Since its first description, EPSmCC has been reported in virtually all anatomical sites, including: gynecologic organs (ovary and cervix); genitourinary organs (urinary bladder and prostate); the gastrointestinal tract (esophagus); skin (Merkel cell carcinoma) and head and neck region. Regardless of the anatomic sites, all SmCCs have similar, if not identical, histo-pathology features and immunohistochemical profile. SmCC is one of the most aggressive malignancies. The molecular mechanisms underlying its development and progression remain poorly understood. Herein, we reviewed the literature in SmCC in respect to its site of occurrence, clinical features, immunohistochemical characteristics. SmCCs have heterogeneous molecular mutations. Dinstinct genetic alterations associated with SmCC from different body sites were reviewed. Some genetic alterations such as RB1, TP53 are commonly seen in different origins of SmCC. Other genes with site specificity were also summarized, such as bladder SmCC with TERT promoter mutations; prostate SmCC with ERG translocations; ovarian SmCC with SMARCA4 mutations; Merkel cell carcinoma (skin) and cervical SmCC with Merkel cell polyomavirus (MCV or MCPyV) and human papillomavirus (HPV). Further studies are needed to employ a genetically oriented approach for the diagnosis and therapy of SmCC.

DNA damage response and its clinicopathological relationship in appendiceal tumors

BACKGROUND

Appendiceal tumors are rare, and their pathogenesis is not well known. DNA damage response (DDR) is a sequence from the detection of damaged DNA to the repair, and its impairment is implicated in the progression of cancers. The aim of the current study is to explore the expression and phosphorylation of checkpoint kinase 2 (Chk2) and TP53, which are key molecules in DDR, and their clinicopathological correlation in the appendiceal tumors.

METHODS

Chk2, phosphorylated Chk2 (pChk2), and TP53 were immunostained in 4 cases of adenoma (AD), 5 non-mucinous adenocarcinomas (AC), 29 low-grade appendiceal mucinous neoplasms (LAMN), and 7 mucinous adenocarcinomas (MAC). Ki-67 labeling index was also evaluated by immunostaining.

RESULTS

Chk2 was highly expressed in the nuclei of all the appendiceal tumors. While pChk2 was high in AD, LAMN, and MAC, it was reduced in AC. Nuclear positive reaction of TP53 was lower in LAMN compared with those of other tumors. The Ki-67 labeling index was slightly lower in LAMN than those in other tumors. The recurrence and death in LAMN is infrequent compared with those in AC and MAC.

CONCLUSIONS

The current study suggested the impairment of DDR in AC and MAC. DDR appeared to be preserved in LAMN, and it may account for low proliferating activity and a favorable clinical course in LAMN.

High-level microsatellite instability in appendiceal carcinomas

High-level microsatellite instability (MSI-high) is found in approximately 15% of all colorectal adenocarcinomas (CRCs) and in at least 20% of right-sided cancers. It is most commonly due to somatic hypermethylation of the MLH1 gene promoter region, with familial cases (Lynch syndrome) representing only 2% to 3% of CRCs overall. In contrast to CRC, MSI-high in appendiceal adenocarcinomas is rare. Only 4 MSI-high appendiceal carcinomas and 1 MSI-high appendiceal serrated adenoma have been previously reported, and the prevalence of MSI in the appendix is unknown. We identified 108 appendiceal carcinomas from MD Anderson Cancer Center in which MSI status had been assessed by immunohistochemistry for the DNA mismatch-repair proteins MLH1, MSH2, MSH6, and PMS2 (n=83), polymerase chain reaction (n=7), or both (n=18). Three cases (2.8%) were MSI-high, and 1 was MSI-low. The 3 MSI-high cases included: (1) a poorly differentiated nonmucinous adenocarcinoma with loss of MLH1/PMS2 expression, lack of MLH1 promoter methylation, and lack of BRAF gene mutation, but no detected germline mutation in MLH1 from a 39-year-old man; (2) an undifferentiated carcinoma with loss of MSH2/MSH6, but no detected germline mutation in MSH2 or TACSTD1, from a 59-year-old woman; and (3) a moderately differentiated mucinous adenocarcinoma arising in a villous adenoma with loss of MSH2/MSH6 expression, in a 38-year-old man with a strong family history of CRC who declined germline testing. When the overall group of appendiceal carcinomas was classified according to histologic features and precursor lesions, the frequencies of MSI-high were: 3 of 108 (2.8%) invasive carcinomas, 3 of 96 (3.1%) invasive carcinomas that did not arise from a background of goblet cell carcinoid tumors, and 0 of 12 (0%) signet ring and mucinous carcinomas arising in goblet cell carcinoid tumors. These findings, in conjunction with the previously reported MSI-high appendiceal carcinomas, highlight the low prevalence of MSI in the appendix as compared with the right colon and suggest that MLH1 promoter methylation is not a mechanism for MSI in this location.

[Gastrointestinal mixed adenoneuroendocrine carcinomas. An attempt at classification of mixed cancers]

Mixed adenoneuroendocrine carcinomas (MANECs) are a challenge for the diagnostics and the concept of a histogenetic tumor typing. They are classified into three malignant subgroups: high grade malignant MANECs combine an adenoma or adenocarcinoma with a small cell or large cell neuroendocrine carcinoma, intermediate grade malignant MANECs consist of a neuroendocrine tumor (NET grade 1 or 2), often a globlet cell carcinoid and a poorly differentiated adenocarcinoma or diffuse carcinoma of signet ring cell type. The prototype of a low grade malignant MANEC is the globlet cell carcinoid. Molecular analysis indicates a common clonal origin of the different components in MANECs. The prognosis is determined by the most aggressive tumor component. The pathogenesis of MANECs is apparently a sequence of increasing malignant transformation which leads either from an adenoma/adenocarcinoma to a small or large cell neuroendocrine carcinoma or from a neuroendocrine tumor (NET), often a globlet cell carcinoid to a poorly differentiated adenocarcinoma or a diffuse carcinoma of signet ring cell type.

Extrapulmonary small cell carcinoma: a clinicopathological study with identification of potential diagnostic mimics

AIMS

To evaluate the clinicopathological features of small cell carcinoma arising outside the lung.

METHODS AND RESULTS

Thirty-seven cases with a pathology diagnosis of extrapulmonary small cell carcinoma (EPSCC) were selected. The clinical notes were reviewed and tumour blocks were selected for a fresh haematoxylin and eosin (H&E) section and immunohistochemical stains. The most common tumour locations were cervix and bladder. Twenty-five cases (68%) were finally diagnosed as EPSCC, nine of which were found with coexisting non small cell carcinoma. Two cases (5%) were diagnosed as large cell neuroendocrine carcinoma (LCNEC) of the cervix. The remainder was classified as 10 poorly differentiated carcinomas (PDCs) (27%). Positive staining for thyroid transcription factor 1 (TTF-1) was noted in nine cases of EPSCC and in none of the cases of PDC (P = 0.034). Synaptophysin immunoreactivity was found in 20 cases of EPSCC and two cases of PDC with neuroendocrine differentiation (P = 0.002), as well as two cases of LCNEC. 34βE12 was positive in eight cases of SCC and two cases of PDC.

CONCLUSIONS

Based on this series, EPSCC may be overdiagnosed. Immunohistochemistry for TTF-1, used in combination with synaptophysin, may help to discriminate EPSCC from PDC.

[Neuroendocrine neoplasms of the appendix and colorectum]

Appropriate diagnosis and treatment of neuroendocrine neoplasms (NENs) of the appendix and colorectum requires a detailed knowledge of their proper classification according to the updated WHO and TNM systems. The WHO classification distinguishes well differentiated NEN, the neuroendocrine tumors (G1 and G2 NETs), from the poorly differentiated carcinomas (G3 NECs). While NETs are common in the appendix and rectum, NECs occur predominantly in the colon. G1 appendiceal and rectal NETs of 1 cm in size or below that do not invade either the muscular wall or vessels bear almost no metastatic risk and can be treated by appendectomy or endoscopic resection. G2 appendiceal and rectal NETs larger than 1 cm in size in combination with other risk factors have an increased risk of metastasis and need to be treated more aggressively. NECs of the colon usually require chemotherapy in addition to resection. Today, most patients with NETs of the appendix and rectum have an excellent prognosis when these diagnostic and therapeutic guidelines are borne in mind.

Classification and pathology of gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are composed of cells with a neuroendocrine phenotype. The old and the new WHO classifications distinguish between well-differentiated and poorly differentiated neoplasms. All well-differentiated neoplasms, regardless of whether they behave benignly or develop metastases, will be called neuroendocrine tumours (NETs), and graded G1 (Ki67 <2%) or G2 (Ki67 2-20%). All poorly differentiated neoplasms will be termed neuroendocrine carcinomas (NECs) and graded G3 (Ki67 >20%). To stratify the GEP-NETs and GEP-NECs regarding their prognosis, they are now further classified according to TNM-stage systems that were recently proposed by the European Neuroendocrine Tumour Society (ENETS) and the AJCC/UICC. In the light of these criteria the pathology and biology of the various NETs and NECs of the gastrointestinal tract (including the oesophagus) and the pancreas are reviewed.

Mixed adenocarcinoma-carcinoid (collision tumor) of the appendix

OBJECTIVE

To report a case of mixed adenocarcinoma and carcinoid in the gastrointestinal tract.

CLINICAL PRESENTATION AND INTERVENTION

A 52-year-old man presented with a mass at the base of the appendix. On microscopic examination of the tumor, mixed adenocarcinoma and carcinoid was identified. The carcinoid component was insular/trabecular in morphology, and the epithelial component revealed mucinous adenocarcinoma. Morphologically and immunohistochemically the 2 components showed a clear-cut distinction, without any intervening intermediate cell population. The adenocarcinomatous component displayed omental deposit and metastasis to the regional lymph nodes. One year later, the patient developed multiple metastatic deposits of adenocarcinoma in the liver, rectus muscle, ileum and sigmoid colon.

CONCLUSION

This tumor had an aggressive clinical course and behaved more like adenocarcinoma than carcinoid.

Pathology of gastrointestinal disorders

Nonneoplastic and neoplastic proliferative lesions of endocrine cells of the gastrointestinal tract are detailed. A multistep continuum from hyperplasia, dysplasia to neoplasia is identified for histamine-producing enterochromaffin-like (ECL) cells of the gastric corpus. Most gastric neuroendocrine tumors (NETs) are silent and composed by ECL cells, the second most frequent neuroendocrine neoplasms being the high-grade neuroendocrine carcinoma (NEC). In the duodenum, preneoplastic lesions are similarly described for gastrin (G) and somatostatin (D) cells. G-cell NETs are the most frequent neuroendocrine tumors of the duodenum, either functioning or nonfunctioning, followed by D-cell NETs and gangliocytic paraganglioma (GCP). No systematic definition of nonneoplastic lesions exists for endocrine cells of the ileum, appendix, and colon-rectum. The most frequent ileal NETs are serotonin-producing enterochromaffin (EC)-cell NETs (classic carcinoid), associating with functional syndrome only in presence of liver metastases. Neoplasms are usually larger in the colon as compared with the small lesions observed in the rectum. High-grade NECs are observed in the colon and rectum-sigmoid, often associate with nonendocrine neoplastic components, and fare an aggressive course with poor outcome and short survival.

Pathologic research update of colorectal neuroendocrine tumors

Colorectal neuroendocrine tumors (NETs) originate from neuroendocrine cells in the intestinal tract, and represent a small area within oncology, but one which has provided increasing new data during the past years. Although the World Health Organization has determined clinical and histological features to predict prognosis for such tumors, they may not be valid on an individual basis. We aim to give an overview of the recent findings with regard to pathology, molecular genetics and diagnosis of NETs.

Extrapulmonary small cell carcinoma localized in lymph nodes: is it a different clinical entity?

BACKGROUND

Extrapulmonary small cell carcinomas (EPSCC) can clinically progress differently depending on the primary site of disease involvement. This review is focused on patients with small cell carcinoma (SmCC) exclusively localized in a lymph node or in multiple lymph nodes without any evidence of a primary tumor in any other organ.

METHODS

We searched the period 1980 to 2007 in the PubMed database and identified 11 publications in the English language presenting at least one case of SmCC. In total 28 individual patients were included in the present study. They were scrutinized in terms of epidemiology, clinical presentation, staging, pathology, etiology, treatment and prognosis.

RESULTS

Characteristics such as age, gender and smoking were similar to those seen in other EPSCCs. Median survival was not reached (42+, range, 9.1 to 100 months). The survival rate was found to be 79% at 3 years. Seventy-seven percent of the patients had limited stage disease. These patients completely responded to surgical therapy, chemotherapy, radiotherapy or to a combination of these treatments. Seventy-one percent of the patients with limited stage SmCC localized in lymph nodes were recurrence-free during the study periods.

DISCUSSION

Our review patient group with SmCC localized in lymph nodes exhibited an excellent clinical behavior and survival results when compared to other patients with pulmonary and non-pulmonary SmCCs. SmCCs localized in lymph nodes may be a separate clinical entity.

A case of uterine cervical adenocarcinoma associated with small cell carcinoma

Extrapulmonary small cell carcinomas are often associated with carcinomas of other cell types. Although a hypothesis that extrapulmonary small cell carcinomas arise from a multipotential stem cell could explain this mixed feature, recent molecular evidence supports another possibility that the small cell component may arise as a late-stage phenomenon in the progression of more organ-typical carcinomas. Here, we report a case of uterine cervical adenocarcinoma containing 30% of small cell carcinoma. Adenocarcinoma was located in the endometrial side of the tumor that was adjacent to the normal cervical region, while small cell carcinoma was located in the periphery of the tumor. The transition from adenocarcinoma to small cell carcinoma was observed in the boundary area. These findings suggest that cervical small cell carcinoma can be differentiated from pre-existing adenocarcinoma and offer further support to the hypothesis that the small cell component arises as a late-stage phenomenon in the progression of more organ-typical carcinomas.

High-grade neuroendocrine carcinoma presenting as an abscess: diagnosis by fine needle aspiration and review of the literature

Neuroendocrine carcinomas (NEC) comprise about 2% of all carcinomas. Review of the literature indicates only a few cases of NEC presenting as an abscess, all having been diagnosed by tissue biopsy. Here, we report the FNA diagnosis of a high-grade neuroendocrine carcinoma presenting as an abscess of the axilla/chest wall in a 68-year-old man and review the pertinent literature.

Small cell carcinoma of the appendix

Background

An extrapulmonary small cell carcinoma is a rare condition. It has similar histological features to pulmonary small cell carcinoma and is equally aggressive.

Case presentation

We present the case of a 60-year-old woman who presented with right upper quadrant pain. Computerised tomography revealed an appendiceal lesion and multiple liver metastases. Exploratory laparotomy and right hemicolectomy was performed with histopathological analysis confirming a primary small cell carcinoma of her appendix.

Conclusion

This is the first reported case of a pure extrapulmonary carcinoma arising from the appendix.

Site-specific biology and pathology of gastroenteropancreatic neuroendocrine tumors

The gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are composed of cells with a neuroendocrine phenotype. Well-differentiated tumors, well-differentiated carcinomas, poorly differentiated carcinomas, functioning tumors (with a hormonal syndrome), and nonfunctioning tumors are identified. To predict their clinical behavior, these neuroendocrine tumors are classified on the basis of their clinicopathological features, including size, local invasion, angioinvasion, proliferative activity, histological differentiation, and metastases, into neoplasms with benign, uncertain, low-grade malignant and high-grade malignant behavior. In addition, a tumor/nodes/metastases classification and a grading system are presented. In the light of these criteria, the various GEP-NET entities are reviewed.

Goblet cell carcinoids and other mixed neuroendocrine/nonneuroendocrine neoplasms

Within the spectrum of neuroendocrine tumors arising in different organs, intermediate and controversial entities exist displaying a coexistence of neuroendocrine and nonneuroendocrine cell populations, and that are grouped under terms such as "goblet cell carcinoid", "mixed endocrine-exocrine carcinoma", "combined carcinomas", or "adenocarcinoma with neuroendocrine differentiation". These tumors may display variable amounts of the two components, potentially ranging from 1 to 99%, and variable structural patterns, ranging from single scattered neuroendocrine cells to a well-defined neuroendocrine tumor cell component organized in typical organoid, trabecular, or solid growth patterns. Although variably included in the site-specific World Health Organization classification schemes, clear definitions and diagnostic features are still missing, as well as a definite knowledge of their biological properties and histogenesis. In the present report, the main characteristics of tumors showing mixed neuroendocrine and nonneuroendocrine features will be described, using morphological patterns and site of origin as schematic guidelines. Moreover, molecular and clinical aspects, which might help to understand their possible histogenesis and biological behavior, will be reviewed.

The pathology of extrapulmonary small cell carcinoma

Extrapulmonary small cell carcinomas (EPSCCs) are uncommon malignant neoplasms with a reported incidence of 0.1% to 0.4% in the United States. Since their first description in 1930, they have been seen in nearly every organ system. Like their more common pulmonary counterparts, EPSCCs are thought to arise from a multipotential stem cell. However, there is recent molecular evidence that small cell elements may arise as a late-stage phenomenon in the genetic progression of more organ-typical carcinomas. The morphologic, immunohistochemical, and ultrastructural features are similar to those described in pulmonary small cell carcinomas (PSCCs). The differential diagnosis of EPSCC includes PSCC, other neuroendocrine tumors, small round blue cell tumors, metastatic melanoma, lymphoma, and poorly differentiated non-small cell carcinomas. Molecular alterations reported to occur in EPSCCs include abnormalities described in PSCC and changes found in carcinomas more typically encountered in the organ from which they arise. In this article we discuss the pathology of EPSCC with a review of theories of histogenesis, sites of occurrence, diagnostic features, differential diagnosis, molecular alterations, and clinical behavior.

Molecular genetic events in gastrointestinal and pancreatic neuroendocrine tumors

Gastrointestinal and pancreatic neuroendocrine tumors originate from the cells of the diffuse endocrine system. Their molecular genetic mechanism of development and progression is complex and remains largely unknown, and they are different in genetic composition from the gastrointestinal epithelial tumors. The current literature suggests that multiple genes are involved in their tumorigenesis with significant differences for tumors of different embryological derivatives: foregut, midgut and hindgut. The MEN1 gene is involved in initiation of 33% of foregut gastrointestinal neuroendocrine tumors. 18q defects are present almost exclusively in mid/hindgut neuroendocrine tumors. X-chromosome markers are associated with malignant behavior in foregut tumors only. Analysis of poorly differentiated neuroendocrine carcinomas of any site demonstrates high chromosomal instability and frequent p53 alterations similar to other poorly differentiated carcinomas. Several factors played a limiting role in the molecular studies published to date: the tumors are rare and heterogeneous, it is difficult to predict their behavior and prognosis, and several different tumor classifications are used by the investigators in the studies. Future studies need to evaluate molecular genetic composition of large series of gastrointestinal and pancreatic neuroendocrine tumors of each specific tumor type. Understanding of specific genetic alterations characteristic for gastrointestinal and pancreatic neuroendocrine tumors might lead to their improved diagnosis, morphologic and molecular characterization and treatment.

[Mixed endocrine tumors]

Mixed endocrine tumors are tumors composed of at least two distinct tumor populations, one of which is endocrine. Because of their rarity and unusual presentation, endocrine mixed tumors raise many problems of diagnosis, management and therapy. Three main types of endocrine mixed tumors are recognized: The existence of these various types has been confirmed by recent molecular studies, even if the same studies have also shown that the histogenesis of a mixed endocrine tumor cannot be predicted from its histological features. Composite tumors are the less rare mixed tumors. The recent WHO classification recommends to restrict the term of composite endocrine tumor to the epithelial tumors containing at least 30% of obviously tumoral endocrine cells; some authors recommend to use higher thresholds, of at least 50%, in order to avoid overdiagnosis. The endocrine component is usually well differentiated, easily identified by its suggestive histological features; the endocrine nature of tumor cells is confirmed by the immunodetection of specific endocrine and neuro-endocrine markers (such as chromogranin A and synaptophysin). In some cases, the endocrine component is poorly differentiated: the demonstration of neuro-endocrine markers is necessary to confirm the diagnosis. Mixed tumors can occur in every anatomical site; they are more frequent in organs containing endocrine cells in the normal state (especially the digestive tract and the pancreas), but they can also be observed in organs devoid of endocrine cells (such as the mammary gland). The management of mixed endocrine tumors must take into account the more aggressive component. Mixed tumors containing a well differentiated endocrine component and an adenocarcinomatous component are to be treated like adenocarcinomas. Mixed tumors containing a poorly differentiated endocrine component must be considered as poorly differentiated endocrine carcinomas.

Évaluation de la malignité dans les tumeurs endocrines digestives : recommandations pratiques

For a long time, the assessment of malignancy risk and patient outcome in digestive endocrine tumors had to rely on sparse and mostly unconfirmed data. The 2000 WHO classification with its standardized scheme of pathologic report constitutes a framework facilitating the assessment of tumor malignancy and has been regarded to be useful for clinical purposes, providing the basis for proper patient management and for designing treatment protocols. The classification is based on a combination of pathological and clinical features with parameters specific for each organ in which the endocrine tumors originate. Three main categories are considered: 1) well differentiated endocrine tumors, further subdivided into tumors with benign and with uncertain behavior; 2) well differentiated endocrine carcinomas, low grade; and 3) poorly differentiated endocrine carcinomas, high grade. In this review the differential tumor characteristics between the above categories are summarized. The relevance of additional features as for tumor prognostication, chiefly the Ki67 proliferation index and malignancy associated genetic changes, is discussed with emphasis on the discrepancies emerging between tumors of foregut and midgut origin.

Epidemiology, tumour biology and histopathological classification of neuroendocrine tumours of the gastrointestinal tract

The diffuse neuroendocrine cell gives rise to a heterogeneous population of tumours which differ in their morphological and functional features. The term 'carcinoid', although well established in medical terminology, is therefore no longer adequate to cover the entire spectrum of neuroendocrine neoplasms. Here we use the term neuroendocrine tumours (NET), which was suggested in the WHO classification of 2000, and review the most important NET entities that are currently recognised in the gastrointestinal tract, highlighting their distinguishing features.

Endocrine tumours of the gastrointestinal tract: aetiology, molecular pathogenesis and genetics

Endocrine tumours of the gut and pancreas originate from cells of the diffuse endocrine system and are characterised by the production of a wide variety of bioactive substances including growth factors. Two major tumour categories are distinguished-well-differentiated and poorly differentiated neoplasms-with distinct phenotypes and significantly diverse clinical behaviour. Here, genetic background data are summarised on an anatomical basis for tumours of foregut, midgut and hindgut derivatives. For well-differentiated tumours, independent techniques identified the abnormality of multiple chromosomal sites and genes, pointing to a complex genetic background. Differences in foregut tumours compared with midgut and hindgut tumours are, however, outlined. The multiple endocrine neoplasia syndrome type 1 (MEN1) gene is reported to be involved in about one-third of sporadic foregut endocrine tumours and exceptionally in midgut and hindgut tumours. Similarly, X chromosome markers are associated with malignant behaviour in foregut tumours only. For poorly differentiated carcinomas, a high degree of chromosomal instability is the common genetic trait independent of tumour site and frequently involving the p53 gene.

Primary epithelial neoplasms and other epithelial lesions of the appendix (excluding carcinoid tumors)

Epithelial tumors of the appendix range from low-grade mucosal-based tumors which, when confined to the appendix, have an excellent prognosis but, once outside the appendix, have a fair prognosis and often a prolonged disease course, to high grade invasive carcinomas that are rapidly fatal. Low grade mucinous neoplasms may rupture and spread to the peritoneum as pseudomyxoma peritonei, and the nomenclature of these tumors has been the subject of considerable disagreement among pathologists; the designation "low grade appendiceal mucinous neoplasm" has recently been proposed for reasons discussed herein. Demonstrating rupture of these neoplasms may require particularly diligent gross and microscopic evaluation as the rupture site often heals over leaving only subtle evidence of its presence. Invasive adenocarcinomas are often mucinous and may also spread to the peritoneum. Against this backdrop, the clinical and pathologic features of low grade appendiceal mucinous neoplasms and mucinous adenocarcinomas, as well as other types such as typical colorectal type and signet-ring cell type, are reviewed. In addition, emerging entities, serrated polyps and serrated adenomas, whose significance is only beginning to be understood, are considered. Retention cysts, hyperplastic polyps, and diffuse mucosal hyperplasia, although not necessarily neoplastic, are reviewed here as they may enter into the differential diagnosis of appendiceal mucinous neoplasms.