Papillary Lesion in the Prostatic Urethra of an Adult

Specimen Type:

Prostate

History:

A 56-year-old male presented with hematuria, and cystoscopy showed a papillary tumor at the prostatic urethra. Transurethral resection was performed, and multiple fragments of tissue ranging from 0.5cm to 0.8cm (1.7cm in aggregate) were submitted entirely.

Pathologic Features:

At low magnification, the lesion is composed of acini with complex papillae (figure 1) and branching papillae at the mucosal surface (figure 2). The papillae are lined by variably stratified columnar epithelium. The lining cells show apically located nuclei (figures 3, 4). There is minimal nuclear pleomorphism, but scattered prominent nucleoli are present (Fig 5). Immunostains for high molecular weight keratin (34βE12) reveals an absent basal cell layer in most of these acini (figure 6) and PSA is positive in the lining epithelium.

Differential Diagnosis:

  • Prostatic urethral epithelial polyps (fig 7)
  • llous adenoma of prostatic urethra (Fig 8)
  • High-grade prostatic intraepithelial neoplasia (fig 9)
  • Prostatic ductal adenocarcinoma (fig 10, 11)

Prostatic urethral epithelial polyps: A variety of diagnostic labels have been affixed to this entity, including ectopic prostatic tissue, benign polyps with prostatic-type epithelium, adenomatous polyps with prostatic-type epithelium, villous polyp, papilloma, papillary adenoma, urethral adenoma, glandular polyps, and even prostatic caruncle. A classic history is that of hematuria in a young man. By cystourethroscopy, a small (usually less than 1cm) papillary or frondlike exophytic mass is seen within the verumentanum. Microscopically, there is papillary growth with true fibrovascular cores lined by unremarkable prostatic epithelium. The epithelium composed of secretory columnar cell layer with underlying basal cells. Small foci of residual urothelium may be present. Cytologically, the secretory cells are bland looking and shows no nuclear abnormalities such as nucleomegaly or nucleolomegaly. The prostatic origin of the proliferation can be confirmed by positive staining for PAP or PSA. Prostatic urethral epithelial polyps are benign lesions that are treated by cystoscopic excision and/or fulguration. Rarely this lesion may recur (reference 1).

Villous adenoma of prostatic urethra: Villous adenomas are rare in the prostatic urethra (reference 2). These adenomas are identical to those seen in colon, with stratification of elongated atypical nuclei, goblet cells, and mitotic figures; PSA is negative in the epithelium. In one case, mucinous adenocarcinoma was reported to arise from prostatic urethral villous adenoma.

High-grade prostatic intraepithelial neoplasia: High-grade prostatic intraepithelial neoplasia can occur in periurethral prostatic duct, characterized by large acini with proliferative changes, including nuclear overlapping, nuclear enlargement and hyperchromatia, as well as scattered prominent nucleoli. Complex branching papillae are usually beyond the expectation of HGPIN. Immunostain for basal cell specific markers reveals intact or fragmented basal cell layer.

Prostatic ductal adenocarcinoma: Ductal carcinoma (adenocarcinoma with endometrioid features; papillary carcinoma, endometrioid carcinoma) accounts for about 0.8% of prostatic adenocarcinoma. It typically arises as a polypoid or papillary mass within the prostatic urethra and/or large periurethral prostatic ducts, and histologically resembles endometrial adenocarcinoma of the female uterus. Clinically, serum concentrations of PSA and PAP may be normal at the time of diagnosis except in patients with bone metastases.

Diagnosis:

Prostatic ductal adenocarcinoma-unique pattern with nuclei on surface

Key Features:

  • Acini with compex branching papillae
  • Variable nuclear pleomorphism; prominent nucleoli are usually present at least focally
  • Basal cells absent or present focally
  • Positive PSA staining in epithelium

Table 1 compares prostatic urethral epithelial polyps and ductal adenocarcinoma

  Prostatic urethral epithelial polyps Ductal adenocarcinoma
Clinical History Young man with hematuria Exclusively older man with obstruction and hematuria
Gross findings: (cystourethroscopy) Small papillary structures on verumontanum, < 1cm in diameter multiple friable polypoid masses near verumontanum, bigger in size
Microscopic findings:
Achitecture
Papillary to polypoid structures, or acini with complex papillae Complex branching papillae or dilated acini
Lining epithelium Basal cell layer (34BE12) Prostatic (PSA positive) to transitional epithelium, intact Prostatic epithelium (PSA positive) Absent of fragmented focally
Cytology Bland, similar to normal prostatic epithelium Nuclear atypia ranging from mild to marked, including nuclear and nucleolar enlargement

Comment: Ductal carcinoma is a common histologic variant of prostatic carcinoma, accounting for 3.2% (pure ductal and mixed ductal-acinar) of all prostatic carcinoma. Ductal carcinoma can be minimal in cytologic abnormalities as seen in this case, which can be potentially confused with benign proliferative processes, such as villous adenoma, prostatic urethral polyps. However, if numerous cleftlike spaces or complex branching papillary architectures are visualized, ductal carcinoma should be suspected. The definitive diagnosis of ductal carcinoma can be further established by positivity for PSA and lack of basal cell layer by high molecular weight cytokeratin (34BE12 or CK5/6) or p63. High-grade prostatic intraepithelial neoplasia may have papillary pattern, but usually does not show complex branching architecture. The unique feature seen in this case is the pattern with apically located nuclei.

References:

  1. Furuya S, Ogura H, Shimamura S, Itoh N, Tsukamoto T, Isomura H. Clinical manifestations of 25 patients with prostatic-type polyps in the prostatic urethra. Hinyokika Kiyo. 2002 Jun;48(6):337-42.
  2. Algaba F, Matias-Guiu X, Badia F, Sole-Balcells F. Villous adenoma of the prostatic urethra. Eur Urol. 1988;14(3):255-7.