Ductal adenocarcinoma of the prostate

Ductal adenocarcinomas of the prostate or prostatic ductal adenocarcinomas are malignant glandular neoplasms of the prostate and tend to be more aggressive than acinar adenocarcinomas.

Terminology

Due to its morphologic resemblance, it has been formerly referred to as 'endometrial' or 'endometrioid carcinoma' of the prostate.

Epidemiology

Ductal adenocarcinomas of the prostate are the second most common malignant tumours of the prostate gland after acinar adenocarcinomas. They make up for about 3-5 % of prostate cancers ^1,2 as mixed ductal-acinar adenocarcinomas and are (≤1%) in isolation ^2-4.

Associations

Ductal adenocarcinomas of the prostate most frequently occur as mixed ductal-acinar adenocarcinomas ².

Clinical presentation

Due to their location, they often present with haematuria or voiding symptoms. More peripherally located ductal adenocarcinomas often present like acinar adenocarcinomas with elevated serum prostate-specific specific antigen (PSA) levels, which tend to be lower than in acinar adenocarcinoma, however, ¹.

Complications

Ductal adenocarcinomas of the prostate can metastasize into the penis, testis, lung, or brain ^1,3.

Pathology

Ductal adenocarcinomas of the prostate are a histological subtype characterised by large cancerous glands coated with columnar epithelial cells with rich cytoplasm and stratified nuclei ^2-4.

Ductal adenocarcinomas often present with high Gleason grades, in particular, if they are cribriform or solid or if necrosis is present ^2,4.

Location

Ductal adenocarcinomas of the prostate are frequently located in the peripheral zone if they are mixed with acinar adenocarcinoma. In their pure form, they might be found in the periurethral area arising from the central periurethral ducts possibly protruding into the urethra ^1,2.

Classification

Ductal adenocarcinomas of the prostate can be classified into the following subtypes ^2,3,5:

• cribriform
• papillary
• solid

Macroscopic appearance

Macroscopically ductal adenocarcinomas of the prostate are similar to acinar adenocarcinoma if located peripherally; if they arise from the verumontanum, they often present as exophytic polypoid or villous masses ¹.

Microscopic appearance

Histologic features of prostatic ductal adenocarcinomas include the following ^1-4:

• cribriform or papillary growth pattern
• elongated pseudostratified nuclei, large nucleoli
• amphophilic and occasionally clear cytoplasm
• coarse chromatin
• intraluminal necrotic debris
• frequently stromal desmoplastic reaction with haemorrhagic inflammation
• possibly perineural invasion

Immunophenotype

Immunohistochemistry stains are usually positive for prostate-specific markers as prostate-specific antigen prostate-specific (PSA), NKX3.1 ², prostate-specific specific membrane antigen (PSMA) or prostate-specific specific acid phosphatase (PAP) ⁶. Basal cell markers are positive in up to 30% ².

Genetics

Fusions of TMPRSS2 and ERG genes are only seen in 10-15% of the cases ¹. Ductal adenocarcinoma cells often show deletions of chromosome 6q15 or the MAP3K7 gene.

Radiographic features

Ductal adenocarcinoma is mainly diagnosed on pathological grounds. Nevertheless, reports have described it as heterogeneous, and cystic components have also been described ⁶.

MRI

Multiparametric MRI can aid in the detection of prostate cancer. Evaluation and reporting should be done using a likelihood score as the PI-RADS system, which deploys different criteria for peripheral and transition zones that are explained in the respective article.

Typical features include the following:

• T1: isointense
• T2: hypointense focus, erased charcoal sign
• DWI: marked diffusion restriction (hyperintense on high b-value and hypointense on ADC map)
• DCE (Gd): focal early enhancement

Radiology report

The radiological report should include a description of the following features:

• form, location and size
• tumour margins
• extraprostatic extension
• seminal vesicle invasion
• bladder or rectal invasion
• suspicious or enlarged lymph nodes 

Treatment and prognosis

Ductal adenocarcinoma is supposed to be more aggressive than acinar adenocarcinoma ⁷.

However, treatment recommendations are not different. Like with acinar adenocarcinoma of the prostate, it is usually dependant on tumour stage and patient preference and includes radical prostatectomy, intensity-modulated or conventional external beam radiotherapy if the first is not possible or available. In addition, the patient might receive androgen deprivation therapy (ADT), and combinations with brachytherapy as well as chemotherapy with docetaxel might be considered.

History and etymology

Ductal adenocarcinomas of the prostate were first described by MM Melicow and MR Pachter in 1967 ⁸.

Differential diagnosis

Ductal adenocarcinoma of the prostate is one subgroup of prostate cancer. The differential diagnosis includes the following conditions ^2-4:

• intraductal carcinoma of the prostate
• high-grade prostatic intraepithelial neoplasia
• acinar adenocarcinoma
• urethral polyp
• urothelial carcinoma involving prostate
• colorectal carcinoma involving prostate
• neuroendocrine tumours of the prostate
• mesenchymal tumours of the prostate