Prostatic stromal hyperplasia with atypia.

Prostatic stromal hyperplasia with atypia (PSHA) is a rare histologic finding diagnosed incidentally on prostate biopsies, transurethral resection specimens, and radical prostatectomy specimens. PSHA has a bizarre histologic appearance and these lesions often raise concern for sarcoma; however, their clinical course is indolent and does not include extraprostatic progression. We discuss a case of PHSA discovered on prostate biopsy performed for an abnormal digital rectal examination and review the literature on this rare pathologic finding.

1. Introduction

Prostatic stromal hyperplasia with atypia (PSHA) is a rare histologic finding diagnosed incidentally in specimens from transrectal ultrasound (TRUS-) guided needle biopsy of the prostate, transurethral resection of prostate (TURP), radical prostatectomy, and simple prostatectomy [1]. Because of their bizarre histologic appearance, these lesions raise concern for sarcoma; however, their clinical course is indolent and does not include extraprostatic progression.

2. Case Presentation

A 55-year-old man underwent a 10-core TRUS biopsy for a grossly abnormal digital rectal exam. Histologic examination (Figure 1) revealed hypercellular stroma with hyperchromatic nuclei around benign prostatic glands in 1 of the 10 cores. There was an absence of adenocarcinoma in the remaining cores. High-power examination revealed smudgy chromatin within these cells (Figure 1 inset). The patient was reassured and placed on watchful waiting with yearly PSA examinations.

Figure 1

H/E stain, low-power magnification (10x) with high-power inset (20x) prostatic tissue showing hypercellular stroma with atypical hyperchromatic nuclei surrounding benign prostatic glands present focally in one of ten needle biopsies. Inset shows a higher power view of the atypical stromal cells with smudgy chromatin and adjacent normal prostatic acinus in lower left.

3. Discussion

PSHA is characterized by one or more ill-defined, uncircumscribed, and hyperplastic stromal nodules infiltrating around benign acini [2]. Immunohistochemical staining further confirms the diagnosis by demonstrating intense immunoreactivity for androgen receptors, while being devoid of activity for estrogen receptors or Ki-67. In contrast with prostatic leiomyoma with atypia, these cells are intensely immunoreactive for vimentin instead of desmin and actin [3].

PSHA does not generally present as a symptomatic lesion in and of itself, though symptomatic cases have been reported [4]. In all cases reported, the portion of tissue comprised of PSHA was between 5–20% of the tissue, with the rest generally being typical nodular hyperplasia [1]. These lesions, despite their atypical appearance, have a universally benign course and no case of metastatic disease has been reported, though some patients undergoing surgical management for BPH have required re-resection [5].

This finding has been referred to by a variety of names including: atypical stromal hyperplasia, symplastic leiomyoma, and pseudoneoplastic lesion of the prostate gland. PSHA was previously grouped with low malignant potential findings such as phyllodes tumor and low-grade sarcoma as stromal tumors of unknown malignant potential (STUMP); however, given the univerally benign course of PSHA, this may constitute a misnomer. The current nomenclature emphasizes the expected indolent clinical course with treatment focused on the original disease of interest [3].