High-Grade Desmoplastic Foamy Gland Prostatic Adenocarcinoma

Context.-It is important to recognize high-grade foamy gland prostatic adenocarcinoma with desmoplastic stroma given its aggressive clinical course with frequent metasta-ses and death. Objective.-To review the morphology, immunohisto-chemistry, and prognosis for this rare subtype of prostate adenocarcinoma.Design.-Twenty-four cases received for consultation from 2010 to 2021 were analyzed including needle biopsy (n = 21), transurethral resection (n = 2), and a cystopros-tatectomy (n = 1).Results.-Patients ranged in age from 40 to 89 years (mean, 67 years). On average, 8 cores per case were involved (mean 67% core involvement). Extraprostatic extension and seminal vesicle invasion were observed in 6 of 21 (29%) and 3 of 21 (14%) needle biopsy cases, respectively. Twenty of the 24 cases (83%) were Grade Group (GG) 5 with 4 of 24 (17%) being GG4. Tumor necrosis as a component of Gleason pattern 5 was observed in 21 of 24 cases (88%). Associated intraductal adenocarcinoma (IDC) was observed in 22 of 24 cases (92%), with 4 of 24 cases (17%) demonstrating extensive IDC. Diagnostic challenges were as follows: (1) sparse isolated cancer glands embedded in the dense desmoplas-tic stroma; (2) fragmented glands; and (3) aberrant staining for high-molecular-weight cytokeratin in a nonbasal cell pattern in all cases. PTEN loss was observed in 9 cases, and p53 nuclear accumulation was observed in 8 cases. Three patients were lost to follow-up. Overall, of the 16 patients with meaningful follow-up, 12 (75%) either had metasta-ses or died from prostate cancer.Conclusions.-High-grade desmoplastic foamy gland adenocarcinoma is difficult to diagnose and grade and has a poor prognosis.