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Open access

Seong Keat Cheah, David Halsall, Peter Barker, John Grant, Abraham Mathews, Shyam Seshadri and Singhan Krishnan

Summary

A frail 79-year-old lady with dementia presented with a 2-year history of frequent falls. Recurrent hypoglycaemic episodes were diagnosed and treated with continuous glucose infusion in multiple hospital admissions. Hypoadrenalism and hypothyroidism were ruled out. Whilst hypoglycaemic (blood glucose 1.6 mmol/L), both plasma C-peptide and proinsulin concentrations, were inappropriately elevated at 4210 pmol/L (174–960) and >200 pmol/L (0–7) respectively with plasma insulin suppressed at 12 pmol/L (0–180). Whilst reported cases of proinsulinoma are typically pancreatic in origin, radiological investigations of the pancreas in this patient did not identify abnormalities. Unexpectedly contrast CT identified a heterogeneously enhancing mass (6.6 cm) at the lower pole of the left kidney consistent with renal cell carcinoma. Non-islet cell tumour-induced hypoglycaemia has been associated with renal malignancy; however, a serum IGF2:IGF1 ratio measured at <10 effectively excludes this diagnosis. Concomitantly on the CT, extensive peripherally enhancing heterogeneous mass lesions in the liver were identified, the largest measuring 12 cm. A palliative approach was taken due to multiple comorbidities. On post-mortem, the kidney lesion was confirmed as clear cell renal carcinoma, whilst the liver lesions were identified as proinsulin-secreting neuroendocrine tumours. In conclusion, the diagnosis of proinsulinoma can be missed if plasma proinsulin concentration is not measured at the time of hypoglycaemia. In this case, the plasma insulin:C-peptide ratio was too high to be accounted for by the faster relative clearance of insulin and was due to proinsulin cross-reactivity in the C-peptide assay. In addition, the concomitant malignancy proved to be a challenging red herring.

Learning points:

  • Even in non-diabetics, hypoglycaemia needs to be excluded in a setting of frequent falls. Insulin- or proinsulin-secreting tumours are potentially curable causes.

  • Whilst investigating spontaneous hypoglycaemia, if plasma insulin concentration is appropriate for the hypoglycaemia, it is prudent to check proinsulin concentrations during the hypoglycaemic episode.

  • Proinsulin cross-reacts variably with C-peptide and insulin assays; the effect is method dependent. In this case, the discrepancy between the insulin and C-peptide concentrations was too great to be accounted for by the faster relative clearance of insulin, raising the suspicion of assay interference. The C-peptide assay in question (Diasorin liaison) has been shown to be 100% cross reactive with proinsulin based on spiking studies with a proinsulin reference preparation.

  • Whilst reported cases of proinsulinoma and 99% of insulinomas are of pancreatic origin, conventional imaging studies (CT, MRI or ultrasound) fail to detect neuroendocrine tumours <1 cm in 50% of cases.

  • The concomitant renal mass identified radiologically proved to be a red herring.

  • In view of the rarity of proinsulinoma, no conclusive association with renal cell carcinoma can be established.

Open access

Joseph A Chorny, John J Orrego and José Manuel Cameselle-Teijeiro

Summary

Most medullary thyroid carcinomas (MTCs) are low grade and produce calcitonin. There are some calcitonin-negative MTCs that produce only calcitonin gene-related peptide (CGRP). Rarely, MTCs are negative for calcitonin and CGRP peptides, but contain their corresponding mRNAs. Primary thyroid neuroendocrine neoplasms other than MTCs are extremely rare. We describe a primary high-grade neuroendocrine carcinoma that was negative for CGRP and calcitonin at both the protein and mRNA levels. A 42-year-old woman presented with a rapidly enlarging thyroid mass replacing most of the left lobe and isthmus. A computed tomography-guided core-needle biopsy was performed. The tumor was composed of sheets of small-to-medium sized epithelial cells. The cells were immunoreactive for pancytokeratin, synaptophysin, CD56 and thyroid transcription factor-1, but negative for CK7, CK20, CD45, CD99, ERG, chromogranin A, thyroglobulin, calcitonin, CGRP and carcinoembryonic antigen. The Ki-67 proliferation index was ~90%. In situ hybridization was negative for calcitonin mRNA. The patient was initially diagnosed as having a small cell carcinoma. She was treated with cisplatin and etoposide (VP16), followed by radiation therapy. Given the excellent clinical course, the tumor was reviewed and reclassified as a high-grade neuroendocrine carcinoma (non-small-cell type). Heretofore, only a few other similar high-grade neuroendocrine tumors with negative markers of C-cell derivation have been reported. In our case, the patient is cancer free five years after diagnosis, but in the other cases, the outcome was poor.

Learning points:

  • There are neuroendocrine carcinomas of the thyroid that do not produce calcitonin or calcitonin gene-related peptide.

  • This category of calcitonin-negative neuroendocrine carcinomas is heterogeneous, consisting of low- and high-grade tumors.

  • The high-grade neuroendocrine carcinomas of the thyroid are rare and generally have a poor prognosis. They are divided into small cell and non-small cell or large cell types.

Open access

Tiago Nunes da Silva, M L F van Velthuysen, Casper H J van Eijck, Jaap J Teunissen, J Hofland and Wouter W de Herder

Summary

Non-functional pancreatic neuroendocrine tumours (NETs) can present with advanced local or distant (metastatic) disease limiting the possibility of surgical cure. Several treatment options have been used in experimental neoadjuvant settings to improve the outcomes in such cases. Peptide receptor radionuclide therapy (PPRT) using beta emitting radiolabelled somatostatin analogues has been used in progressive pancreatic NETs. We report a 55-year-old female patient with a 12.8 cm pancreatic NET with significant local stomach and superior mesenteric vein compression and liver metastases. The patient underwent treatment with [177Lutetium-DOTA0,Tyr3]octreotate (177Lu-octreotate) for the treatment of local and metastatic symptomatic disease. Six months after 4 cycles of 177lutetium-octreotate, resolution of the abdominal complaints was associated with a significant reduction in tumour size and the tumour was rendered operable. Histology of the tumour showed a 90% necrotic tumour with abundant hyalinized fibrosis and haemorrhage compatible with PPRT-induced radiation effects on tumour cells. This report supports that PPRT has a role in unresectable and metastatic pancreatic NET.

Learning points:

  • PRRT with 177Lu-octreotate can be considered a useful therapy for symptomatic somatostatin receptor-positive pancreatic NET.

  • The clinical benefits of PRRT with 177Lu-octreotate can be seen in the first months while tumour reduction can be seen up to a year after treatment.

  • PRRT with 177Lu-octreotate was clinically well tolerated and did not interfere with the subsequent surgical procedure.

  • PRRT with 177Lu-octreotate can result in significant tumour reduction and may improve surgical outcomes. As such, this therapy can be considered as a neoadjuvant therapy.

Open access

Jerena Manoharan, Caroline L Lopez, Karl Hackmann, Max B Albers, Anika Pehl, Peter H Kann, Emily P Slater, Evelin Schröck and Detlef K Bartsch

Summary

We report about a young female who developed an unusual and an aggressive phenotype of the MEN1 syndrome characterized by the development of a pHPT, malignant non-functioning pancreatic and duodenal neuroendocrine neoplasias, a pituitary adenoma, a non-functioning adrenal adenoma and also a malignant jejunal NET at the age of 37 years. Initial Sanger sequencing could not detect a germline mutation of the MEN1 gene, but next generation sequencing and MPLA revealed a deletion of the MEN1 gene ranging between 7.6 and 25.9 kb. Small intestine neuroendocrine neoplasias (SI-NENs) are currently not considered to be a part of the phenotype of the MEN1-syndrome. In our patient the SI-NENs were detected during follow-up imaging on Ga68-Dotatoc PET/CT and could be completely resected. Although SI-NENs are extremely rare, these tumors should also be considered in MEN1 patients. Whether an aggressive phenotype or the occurrence of SI-NENs in MEN1 are more likely associated with large deletions of the gene warrants further investigation.

Learning points

  • Our patient presents an extraordinary course of disease.

  • Although SI-NENs are extremely rare, these tumors should also be considered in MEN1 patients, besides the typical MEN1 associated tumors.

  • This case reports indicate that in some cases conventional mutation analysis of MEN1 patients should be supplemented by the search for larger gene deletions with modern techniques, if no germline mutation could be identified by Sanger sequencing.

Open access

Taiba Zornitzki, Hadara Rubinfeld, Lyudmila Lysyy, Tal Schiller, Véronique Raverot, Ilan Shimon and Hilla Knobler

Summary

Acromegaly due to ectopic GHRH secretion from a neuroendocrine tumor (NET) is rare and comprises <1% of all acromegaly cases. Herein we present a 57-year-old woman with clinical and biochemical features of acromegaly and a 6 cm pancreatic NET (pNET), secreting GHRH and calcitonin. Following surgical resection of the pancreatic tumor, IGF1, GH and calcitonin normalized, and the clinical features of acromegaly improved. In vitro studies confirmed that the tumor secreted large amounts of both GHRH and calcitonin, and incubation of pNET culture-derived conditioned media stimulated GH release from a cultured human pituitary adenoma. This is a unique case of pNET secreting both GHRH and calcitonin. The ability of the pNET-derived medium to stimulate in vitro GH release from a human pituitary-cell culture, combined with the clinical and hormonal remission following tumor resection, confirmed the ectopic source of acromegaly in this patient.

Learning points

  • Signs, symptoms and initial work-up of acromegaly due to ectopic GHRH secretion are similar to pituitary-dependent acromegaly. However, if no identifiable pituitary lesion is found, somatostatin receptor scan and further imaging (CT, MRI) should be performed.

  • Detection of GHRH in the blood and in the tumor-derived medium supports the diagnosis of ectopic GHRH secretion.

  • Functional bioactivity of pNET-secreted GHRH can be proved in vitro by releasing GH from human pituitary cells.