Synaptophysin: neuro-endocrine marker in breast tumors

Synaptophysin is a protein which is present in nearly all neurons in the brain and spinal cord. Its exact function is not known but it is involved in the process of synaptic transmission. Synaptophysin is a38-kDa integral membrane glycoprotein of the presynaptic vesicles in virtually all and neuroendocrine cells. As such, it is used as a marker of neuroendocrine differentiation in tumors, including breast cancer tumors.

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Synaptophysin can be detected through immunochemical staining, and it’s presence in a breast cancer tumor would indicate the prominent involvement of neuro-endocrine cells, and if significant quantities were found, the lesion might be identified as neuro-endocrine breast cancer.

Rate and prognostic significance of synaptophysin differentiation in breast tumors

Neuro-endocrine differentiation in a breast cancer tumor is usually determined a finding of high levels of either synaptophysin, chromogranin A, or both. Primary neuro-endocrine breast cancer is very rare, accounting for less than 0.1% of all breast carcinomas.

But, a certain amount of neuro-endocrine cell involvement in other, generic breast cancers is also not uncommon. The prognostic effect of neuro-endocrine cell involvement is very inconclusive. Recent studies on a variety of breast cancers have shown a positive detection rate for synaptophysin expression of about 5% to 10%.

It has been found that neuro-endocrine differentiation in breast cancers, determined through the positive expression of synaptophysin and chromogramin A, does not carry any special prognostic significance for the course of the disease at all.

Synaptophysin is not associated with breast cancer aggressiveness

Furthermore, synaptophysin appears to be commonly expressed in a whole range of neuro-endocrine breast neoplasms without any particular correlation with other neuro-endocrine markers, such as serotonin and neuropeptides.

The expression of synaptophysin also does not appear to be related to epithelial or cytoskeletal characteristics, or with the clinical aggressiveness of the breast cancer.

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For further reading, I suggest you go to this page for information about neuro endocrine markers, and this page for neuro endocrine breast carcinoma.

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References

1. Uccini, S., Monardo, F., Paradiso, P., Masciangelo, R., Marzullo, A., Ruco, LP, Baroni, CD. Synaptophysin in human breast carcinomas. Histopathology (March 1991)Volume 18, Issue 3, pages 271–273,
2. van Krimpen, C., Elferink, A., Broodman, CA., Hop, WCJ., Pronk, A., Menke, M., The prognostic influence of neuroendocrine differentiation in breast cancer: results of a long-term follow-up study. The Breast Volume 13, Issue 4, August 2004, Pages 329-333
3. Tsuchiya, A., Nozawa, Y., Hasegawa, A., Kishimoto, M., Takenoshita, S., A case of breast cancer with endocrine features. Breast Cancer Volume 7, Number 2, 157-159,
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7. Zekiog(lu O, Erhan Y, Ciris M, Bayramog(lu H. Neuroendocrine differentiated breast carcinoma of the breast: a distinct entity. Breast 2003;12:251-7.
8. Tarsa L, Goda Y. Synaptophysin regulates activity-dependent synapse formation in cultured hippocampal neurons.Proc Natl Acad Sci U S A. 2002 Jan 22;99(2):1012-6. Epub 2002 Jan 15.
9. Gould VE, Wiedenmann B, Lee I, Schwechheimer K, Dockhorn-Dworniczak B, Radosevich JA, Moll R, Franke WW. Synaptophysin expression in neuroendocrine neoplasms as determined by immunocytochemistry. Am J Pathol. 1987 Feb;126(2):243-57.
10. Calhoun ME, Jucker M, Martin LJ, Thinakaran G, Price DL, Mouton PR (December 1996). "Comparative evaluation of synaptophysin-based methods for quantification of synapses". J. Neurocytol. 25 (12): 821–8.

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