Clear cell endocrine tumor of the pancreas which is not associated with von Hippel-Lindau disease: report of a case

Synchronous Periampullary Tumors in a Patient With Pancreas Divisum and Neurofibromatosis Type 1

INTRODUCTION

In this study, we describe for the first time a Neurofibromatosis type 1 patient with pancreas divisum, multiple periampullary tumors and germline pathogenic variants in NF1 and CFTR genes.

CASE REPORT

A 62-year-old female NF1 patient presented with weakness, choluria, nausea, and diffuse abdominal pain to an emergency room service. Magnetic resonance imaging revealed an abdominal mass involving the periampullary region and pancreas divisum. After surgical resection, three synchronous neoplasms were detected including two ampullary tumors (adenocarcinoma of the major ampulla and a neuroendocrine tumor of the minor ampulla) and a gastrointestinal stromal tumor (GIST). Germline multigene panel testing (MGPT) identified two pathogenic heterozygous germline variants: NF1 c.838del and CFTR c.1210-34TG[12]T[5].

CONCLUSION

This is the first report of a Neurofibromatosis type 1 patient with pancreas divisum and multiple periampullary tumors harboring pathogenic germline variants in NF1 and CFTR genes. The identification of two germline variants and a developmental anomaly in this patient may explain the unusual and more severe findings and underscores the importance of comprehensive molecular analyses in patients with complex phenotypes.

Synchronous pancreatic tumors in a patient with history of Wilms tumor: A case of pancreatic adenocarcinoma and lipid-rich neuroendocrine tumor diagnosed by cytopathology

Synchronous tumors represent a very small portion of pancreatic tumors. Although there is a higher incidence of secondary malignant neoplasms (SMN) in patients with history of Wilms tumor (WT), pancreatic tumors are very infrequent SMNs in this population. We report the first case of synchronous pancreatic tumors in a patient with history of WT. Two separated pancreatic lesions were identified by abdominal computerized tomography (CT) scan. Fine-needle aspiration of both lesions was performed for cytopathology examination. A pancreatic adenocarcinoma was diagnosed in the head of pancreas, and the pancreatic body lesion was found to be a neuroendocrine tumor (NET). The NET had characteristic vacuolated lipid-rich cytoplasm. Further molecular testing was done on both tumors, but no common cancer-associated mutation was found.

Recent updates on grading and classification of neuroendocrine tumors

Neuroendocrine tumors (NETs) are originating from neuroendocrine cells in diffuse endocrine systems. NETs are diagnosed by characteristic histologic features and immunoprofiles. Recent 2010 WHO classification for gastroenteropancreatic NETs introduced grading system based on mitotic count and Ki-67 proliferation index. Gastroenteropancreatic NETs are classified as NET grade 1, NET grade 2, and neuroendocrine carcinoma (NET grade 3). However, the carcinoid is still used in classification of NETs of the lung and uterine cervix. Some issues with grading system such as methodologies for evaluation of Ki-67 index and subclassification of neuroendocrine carcinoma (NET grade 3) are arising. The importance of Ki-67 labeling index is emerging in differential diagnosis of lung carcinoids. In this review, we focus on recent grading and classification of NETs and related issues in various organs, including gastrointestinal tract, pancreas, lung, and female reproductive organs.

Recent Updates on Neuroendocrine Tumors From the Gastrointestinal and Pancreatobiliary Tracts

CONTEXT

-Gastrointestinal (GI) and pancreatobiliary tracts contain a variety of neuroendocrine cells that constitute a diffuse endocrine system. Neuroendocrine tumors (NETs) from these organs are heterogeneous tumors with diverse clinical behaviors. Recent improvements in the understanding of NETs from the GI and pancreatobiliary tracts have led to more-refined definitions of the clinicopathologic characteristics of these tumors. Under the 2010 World Health Organization classification scheme, NETs are classified as grade (G) 1 NETs, G2 NETs, neuroendocrine carcinomas, and mixed adenoneuroendocrine carcinomas. Histologic grades are dependent on mitotic counts and the Ki-67 labeling index. Several new issues arose after implementation of the 2010 World Health Organization classification scheme, such as issues with well-differentiated NETs with G3 Ki-67 labeling index and the evaluation of mitotic counts and Ki-67 labeling. Hereditary syndromes, including multiple endocrine neoplasia type 1 syndrome, von Hippel-Lindau syndrome, neurofibromatosis 1, and tuberous sclerosis, are related to NETs of the GI and pancreatobiliary tracts. Several prognostic markers of GI and pancreatobiliary tract NETs have been introduced, but many of them require further validation.

OBJECTIVE

-To understand clinicopathologic characteristics of NETs from the GI and pancreatobiliary tracts.

DATA SOURCES

-PubMed (US National Library of Medicine) reports were reviewed.

CONCLUSIONS

-In this review, we briefly summarize recent developments and issues related to NETs of the GI and pancreatobiliary tracts.

Pancreatic Neuroendocrine Tumors

Pancreatic neuroendocrine neoplasms include well-differentiated pancreatic neuroendocrine tumors (PanNETs) and neuroendocrine carcinomas (NECs) with well-differentiated PanNETs accounting for most cases. Other pancreatic primaries and metastatic carcinomas from other sites can mimic pancreatic neuroendocrine neoplasms. Immunohistochemical studies can be used to aid in the differential diagnosis. However, no specific markers are available to differentiate PanNETs from NETs of other sites. Although NECs are uniformly deadly, PanNETs have variable prognosis. Morphology alone cannot predict the tumor behavior. Although some pathologic features are associated with an aggressive course, Ki67 is the only prognostic molecular marker routinely used in clinical practice.

Pancreatic neuroendocrine tumors: pathologic and molecular characteristics

Pancreatic neuroendocrine neoplasms include mainly well-differentiated neuroendocrine tumors but also rare poorly differentiated neuroendocrine carcinomas. Molecular mechanisms underlying pancreatic neuroendocrine tumorigenesis have recently been elucidated. While alterations in the chromatin remodeling and PI3K/Akt/mTOR pathways are present in most well-differentiated pancreatic neuroendocrine tumors, mutations in TP53 and RB may contribute to the development of pancreatic poorly differentiated neuroendocrine carcinomas. With these discoveries, new molecular targeted therapies have become available and show promise in some patients with pancreatic well-differentiated neuroendocrine tumor.

Lipid-rich ("clear cell") neuroendocrine tumors of the pancreas in MEN I patients

The presence of "clear" or lipid-rich cells within pancreatic neuroendocrine tumors is thought to be pathognomonic of von Hippel-Lindau (VHL) disease, especially in the context of multiple tumors. However, we encountered the presence of lipid-rich cells in six of 16 patients (eight microadenomas/adenomas) who had multiple endocrine neoplasia type I (MEN I). Three of the lesions (two microadenomas and one adenoma) were composed entirely of lipid-rich cells while the remaining five lesions had a component of lipid-rich cells. All lesions containing lipid-rich cells were negative for α-inhibin, but positive for chromogranin and synaptophysin. In addition, four of the eight lesions were glucagon positive. None of the patients had clinical symptoms related to hormone production. We suggest that lipid-rich cells are not reflexly indicative of VHL, and that they may be encountered in a proportion of cases of MEN I either focally or constituting the entire neuroendocrine lesion.

Clear cell neuroendocrine tumor G1 of the gallbladder without von Hippel-Lindau disease

Clear cell neuroendocrine tumor (NET) is a rare but distinct histopathological variant of NET most often observed in patients with von Hippel-Lindau disease (VHL). Clear cell NET in non-VHL patients is extremely rare and this report is only the second to describe a case of clear cell NET G1 (carcinoid tumor) of the gallbladder without VHL. A 71-year-old male without past or family history of VHL presented with a polypoid lesion in the fundus of the gallbladder and laparoscopic cholecystectomy was performed. Histopathological study revealed that the polypoid lesion was comprised of nests or trabecular growths of clear cells without atypia. Immunohistochemically, the neoplastic cells were diffusely positive for endocrine markers, but negative for α-inhibin. Clinicopathological review of cases with clear cell NET G1 of the gallbladder revealed that this disease occurs in patients with or without VHL, but that gallbladder stones and cholecystitis were present in non-VHL cases. We hypothesized that the occurrence of clear cell NET of the gallbladder (particularly non-VHL cases) may be associated with chronic cholecystitis induced by gallbladder stones. Moreover, α-inhibin was detected in clear cell NET tumor cells in one VHL case, but not in two non-VHL cases. These findings suggest that α-inhibin expression is a useful determinant of an association between clear cell NET and VHL.

Pancreatic Endocrine Tumors are a Rare Manifestation of the Neurofibromatosis Type 1 Phenotype

The tumorigenesis of sporadic endocrine tumors is still not fully understood. It is well known that patients with von Recklinghausen syndrome (NF-1) (OMIM 162200) carrying NF1 germline mutations are predisposed to endocrine tumors including pheochromocytomas and duodenal somatostatinomas. It is unclear, however, whether the rarely reported occurrence of pancreatic insulinomas in NF-1 patients represents a coincidental finding or whether insulinomas are a rare manifestation of the NF-1 syndrome. To determine the potential association between the NF-1 syndrome and pancreatic endocrine tumors, we analyzed a NF-1 patient with a well-differentiated pancreatic endocrine carcinoma for NF1 mutation, allelic loss of the NF1 gene and its expression in peripheral blood and tumor cells. The germline mutation c. 499 del TGTT known in the family was confirmed by polymerase chain reaction (PCR) and direct sequencing of exon 4 in DNA extracted from peripheral blood. Loss of heterozygosity (LOH) analysis of the NF1 gene was carried out using 3 intragenic microsatellite markers on 17q11.2. RNA expression was examined by reverse transcription and a consecutive PCR spanning intron 3 of the NF1 gene including the mutated site in exon 4. Immunohistochemistry was used to analyze NF-1 protein expression. Mutation analysis of peripheral blood leukocytes confirmed the 4 base pair deletion in exon 4 starting at codon 167 (499 del TGTT). LOH analysis of tumor tissue revealed retention of both NF1 alleles. While reverse transcriptase-PCR of peripheral blood showed bi-allelic expression of both the wild-type NF1 and the mutated form, reverse transcriptase-PCR of tumor extracts demonstrated expression of the mutated but not the wild-type NF1 allele. Additionally, neurofibromin, the NF1 gene product, was absent in the tumor tissue of the NF-1 patient. These results show that the wild-type NF1 transcrips and protein are reduced, in the reported insulinoma, supposedly by epigenetic mechanisms. This provides strong evidence that there is a relationship between von Recklinghausen disease and the patient's insulinoma. In this line, insulinomas may be viewed as a rare manifestation of the NF-1 syndrome. Furthermore, the NF1 gene must be considered as a candidate tumor suppressor gene for sporadic insulinomas and probably other pancreatic endocrine tumors.

Lipid-Rich Variant of Pancreatic Endocrine Neoplasms

Most pancreatic endocrine neoplasms (PENs) show characteristic and well-recognized endocrine morphology; however, a lipid-rich pattern, which can present a diagnostic problem in biopsies, has been reported, mostly as individual cases. Some have been included in descriptions of the rare clear-cell variant associated with von Hippel-Lindau (VHL) syndrome. The histogenesis, clinicopathologic characteristics, and significance of this lipid-rich pattern have not been unraveled. In this study, 11 PENs exhibiting foamy, microvesicular cytoplasm were analyzed. In some cases, the nuclei were distorted by the vesicles, and the usual endocrine chromatin pattern was not evident. The growth pattern was relatively diffuse, with vague compartmentalization of the cells by a delicate vasculature; prominent nesting was noted in only 4 cases. Pathology reports indicated substantial diagnostic challenge in these cases; on biopsies, 1 case was originally diagnosed as adrenal cortical carcinoma, another as renal cell carcinoma, a third as solid-pseudopapillary tumor, and a fourth had a fine needle aspiration cytologic diagnosis of adenocarcinoma. All cases were chromogranin and synaptophysin positive. Electron microscopy in 3 cases confirmed the cytoplasmic vesicles to be lipid vacuoles. Neurosecretory granules were also evident. Clinically, as in conventional PENs, there appeared to be two distinct subsets: Two cases were familial or functional/syndromic (1 with VHL and the other with MEN-1 and glucagonoma syndrome) and occurred in younger adults (ages 41 and 47 years); the majority (n = 9) were nonfunctional/nonsyndromic and nonfamilial. The latter group was mostly represented by elderly males (mean age: 65 vs. 58 years in conventional sporadic PENs). Immunohistochemically, markers implicated in VHL-associated neoplasia, including HIF-1alpha, inhibin, and Melan-A (in clear-cell PENs) and MUC6 (in serous cystadenomas) were mostly negative in lipid-rich PENs (1 of 10, 1 of 10, 0 of 10 and 0 of 10, respectively). In conclusion, the lipid-rich pattern, reminiscent of adrenal cortical cells, represents a distinct subset of PENs. It presents a diagnostic challenge for surgical pathologists, especially in biopsies. EM supports the name lipid-rich for this variant. The findings suggest that the pathogenesis of lipid-rich tumors may be different from the VHL-associated clear-cell variants of PENs.