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prostate neuroendocrine tumors

Saturday 18 February 2012

Definition

Neuroendocrine differentiation in prostatic carcinoma has three forms:
- 1. Focal neuroendocrine differentiation in conventional prostatic adenocarcinoma
- 2. Carcinoid tumour (WHO well differentiated neuroendocrine tumour)
- 3. Small cell neuroendocrine carcinoma (new WHO classification poorly differentiated neuroendocrine carcinoma)

ICD-O codes

- Focal neuroendocrine differentiation in prostatic adenocarcinoma 8574/3
- Carcinoid 8240/3
- Small cell carcinoma 8041/3

Focal neuroendocrine differentiation in prostatic adenocarcinoma

All prostate cancers show focal neuroendocrine differentiation, although the majority shows only rare or sparse single neuroendocrine cells as demonstrated by neuroendocrine markers.

In 5-10% of prostatic carcinomas there are zones with a large number of single or clustered neuroendocrine cells detected by chromogranin A immunostaining.

A subset of these neuroendocrine cells may also be serotonin positive.

Immunostaining for neuron-specific enolase, synaptophysin, bombesin/gastrin-releasing peptide and a variety of other neuroendocrine peptides may also occur in individual neoplastic neuroendocrine cells, or in a more diffuse pattern and receptors for
serotonin and neuroendocrine peptides may also be present.

Vascular endothelial growth factor (VEGF) may also be expressed in foci of neuroendorine differentiation.

The definitional context of these other neuroendocrine elements (other than chromogranin A and serotonin) remains to be elucidated.

There are conflicting studies as to whether advanced androgen
deprived and androgen independent carcinomas show increased neuroendocrine differentiation.

The prognostic significance of focal neuroendocrine differentiation in primary untreated prostatic carcinoma is controversial with some showing an independent negative effect on prognosis, while others have not shown a prognostic relationship.

In advanced prostate cancer, especially androgen independent cancer, focal neuroendocrine differentiation portends a poor prognosis and
may be a therapeutic target.

Serum chromogranin A levels (and potentially other markers such as
pro-gastin-releasing peptide) may be diagnostically and prognostically useful, particularly in PSA negative, androgen independent carcinomas.

Carcinoid tumours

True carcinoid tumours of the prostate, which meets the diagnostic criteria for carcinoid tumour elsewhere are exceedingly rare.

These tumours show classic cytologic features of carcinoid tumour and diffuse neuroendocrine differentiation (chromogranin A and synaptophysin immunoreativity). They should be essentially negative for PSA. The prognosis is uncertain due to the small number of reported cases.

The term "carcinoid-like tumours" has been used to refer to a variety of miscellaneous entities, most of which refer to ordinary acinar adenocarcinoma of the prostate with an organoid appearance and focal neuroendorcrine immunoreactivity.

Small cell carcinoma

Clinical features

Many patients have a previous history of a hormonally treated acinar adenocarcinoma.

As the small cell carcinoma component predominates, serum PSA level
falls and may be undetectable. While most small cell carcinomas of the
prostate lack clinically evident hormone production, they account for the majority of prostatic tumours with clinically evident ACTH or antidiuretic hormone production.

Histopathology

Small cell carcinomas of the prostate histologically are identical to small cell carcinomas of the lung. In approximately 50% of the cases, the tumours are mixed small cell carcinoma and adenocarcinoma of the prostate.

Neurosecretory granules have been demonstrated within several prostatic small cell carcinomas.

Using immunohistochemical techniques small cell components are negative for PSA and PAP.

There are conflicting studies as to whether small cell carcinoma of the
prostate is positive for thyroid transcription factor-1 (TTF-1), in order to distinguish them from a metastasis from the lung.

Prognosis

The average survival of patients with small cell carcinoma of the prostate is less than a year.

There is no difference in prognosis between patients with pure
small cell carcinoma and those with mixed glandular and small cell carcinoma.

The appearance of a small cell component within the course of adenocarcinoma of the prostate usually indicates an aggressive terminal phase of the disease.

In a review of the literature of genitourinary small cell carcinoma, whereas cisplatin chemotherapy was beneficial for bladder tumours, only surgery was prognostic for prostate small cell carcinomas.

While this study concluded that hormonal manipulation and systemic chemotherapy had little effect on the natural history of disease in the
prostate, the number of patients were small and others suggest to treat small cell carcinoma of the prostate with the same combination chemotherapy used to treat small cell carcinomas in other sites.