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colloid and signet ring prostate acinar adenocarcinoma

Sunday 12 February 2012

Colloid & signet ring variant of prostate cancer; Colloid (mucinous) prostate carcinoma

Using criteria developed for mucinous carcinomas of other organs, the diagnosis of mucinous adenocarcinoma of the prostate gland should be made when at least 25% of the tumour resected contains lakes of extracellular mucin.

On biopsy material, cancers with abundant extracellular mucin should be diagnosed as carcinomas with mucinous features, rather than colloid carcinoma, as the biopsy material may not be reflective of the entire tumour.

Mucinous (colloid) adenocarcinoma of the prostate gland is one of the least common morphologic variants of prostatic carcinoma.

A cribriform patterntends to predominate in the mucinous areas.

In contrast to bladder adenocarcinomas, mucinous adenocarcinoma of the prostate rarely contain mucin positive signet cells. Some carcinomas of the
prostate will have a signet-ring-cell appearance, yet the vacuoles do not
contain intracytoplasmic mucin.

These vacuolated cells may be present as singly invasive cells, in single glands, and in sheets of cells.

Only a few cases of prostate cancer have been reported with mucin positive signet cells.

One should exclude other mucinous tumours of non-prostatic origin based on
morphology and immunohistochemistry and if necessary using clinical information.

Even more rare are cases of in-situ and infiltrating mucinous adenocarcinoma
arising from glandular metaplasia of the prostatic urethra with invasion into the
prostate.

The histologic growth pattern found in these tumours were identical to mucinous adenocarcinoma of the bladder consisting lakes of mucin lined by tall columnar epithelium with goblet cells showing varying degrees of nuclear atypia and in some of these cases, mucin-containing signet cells.

These tumours have been negative immunohistochemically for PSA and PAP.

Mucinous prostate adenocarcinomas behave aggressively. In the largest reported series, 7 of 12 patients died of tumour (mean 5 years) and 5 were alive with disease (mean 3 years).

Although these tumours are not as hormonally responsive as their nonmucinous counterparts, some respond to androgen withdrawal.

Mucinous prostate adenocarcinomas have a propensity to develop bone metastases and increased serum PSA levels with advanced disease.

Grading

The majority of cases with colloid carcinoma consist of irregular cribriform glands floating within a mucinous matrix. It was the uniform consensus that these cases would be scored Gleason score 4+4=8.

However, uncommonly one may see individual round discrete glands floating within mucinous pools. There was no consensus in these cases whether such cases should be diagnosed as Gleason score 4+4=8 or Gleason score 3+3=6.

Approximately half of the group said that by definition all colloid carcinomas should be assigned a Gleason score of 8, while the other half felt that one should ignore the extracellular mucin and grade the tumor based on the underlying architectural pattern.

The excellent prognosis of mucinous carcinomas in a large study of mucinous carcinoma at radical prostatectomy supports grading mucinous prostate carcinomas based on the underlying architectural pattern rather than assuming that all of these tumors are aggressive.