foamy gland prostatic adenocarcinoma

Definition: Foamy gland adenocarcinoma is a variant of prostatic acinar adenocarcinoma that is characterized by abundant foamy cytoplasm and often by pyknotic nuclei.

Clinically, patients with foamy gland carcinoma are of mean age 65 years (range 50–78 years) and present with elevated serum prostate-specific antigen (PSA).

This is similar to what is found for non-foamy usual acinar adenocarcinoma.

Foamy glands can be found admixed with usual acinar adenocarcinoma in 13–23% of radical prostatectomy cases.

Microscopically, there is an architectural pattern of crowded or infiltrative glands.

High-grade growth patterns, in order of frequency of detection, include cribriform, fused/poorly defined glands, cords/single cells, and solid sheets.

Admixture of foamy gland and usual acinar non-foamy gland adenocarcinoma is common, although, in needle biopsy, the carcinoma may be pure foamy gland.

The foamy appearance of the cytoplasm is caused by the presence of numerous intracytoplasmic vesicles, which lack lipid or neutral mucin.

Abundant dense pink amorphous intraluminal secretions may be identified.

Immunohistochemical stains with 34βE12 and/or p63 antibodies demonstrate the absence of a basal cell layer in all cases of invasive foamy gland carcinoma.

Rare cases of intraductal foamy gland carcinoma and foamy gland high-grade prostatic intraepithelial neoplasia have been reported, where basal cells are detected in the neoplastic foamy glands.

AMACR expression can be detected by immunohistochemistry in most (68%) foamy gland carcinomas.

The Gleason grade of foamy gland carcinoma ranges from Gleason score 6–10.

The most common Gleason score is 7. Foamy gland carcinomas are of similar pathological stage as non-foamy adenocarcinomas, and may exhibit extraprostatic extension.

Metastatic deposits can display foamy gland features.

Foamy gland adenocarcinoma does not appear to be different from unusal acinar adenocarcinoma in patient outcome after radical prostatectomy.

Foamy gland carcinoma is a variant of prostatic acinar adenocarcinoma characterized by abundant, foamy cytoplasm, frequently showing small, pyknotic nuclei.

The incidence and Gleason grade of foamy gland carcinoma in a large prostate needle biopsy series have not been established.

Foamy gland carcinoma may be deceptively benign appearing and missed on needle biopsy.

Immunohistochemical staining for basal cells and α-methylacyl-CoA racemase (AMACR) can support a diagnosis of foamy gland carcinoma, but the sensitivity of AMACR for foamy gland carcinoma has been reported to be lower than that for usual acinar carcinoma.

The utility of ERG immunohistochemistry in the diagnosis of foamy gland carcinoma has not been explored.

Foamy gland carcinoma features are relatively common in prostate needle core biopsies, the foamy gland carcinoma is admixed with usual acinar carcinoma in the majority of cases, and is usually not of high Gleason grade, although 20% are Gleason score 7 or greater.

ERG immunohistochemistry did not provide added value beyond AMACR expression in most cases, suggesting that it need not be initially utilized in addition to basal cell markers and AMACR when immunohistochemistry is needed to substantiate a diagnosis of foamy gland malignancy.

Sensitivity of AMACR for foamy gland carcinoma was comparable to that seen in studies of usual acinar carcinoma and is an excellent marker for foamy gland carcinoma of the prostate.

ERG immunohistochemistry could be considered in a second round of immunostaining of select difficult cases of foamy gland carcinoma with low AMACR expression.

References

 Foamy Gland Carcinoma of the Prostate in Needle Biopsy: Incidence, Gleason Grade, and Comparative α-Methylacyl-CoA Racemase vs. ERG Expression. Warrick JI, Humphrey PA. Am J Surg Pathol. 2013 Jun 20. PMID: 23797726

 Histological variants of prostatic carcinoma and their significance. Humphrey PA. Histopathology. 2012 Jan;60(1):59-74. PMID: 22212078