[931] High Grade Prostatic Intraepithelial Neoplasia (HGPIN) and Intraductal Carcinoma of the Prostate (IDC-P):“Small Cell” Variant

Stephen Lee, Jonathan I Epstein. The Johns Hopkins Hospital, Baltimore

Background: “Small-cell HGPIN” is an exceedingly rare variant of HGPIN. The single case in the literature was associated with invasive small cell carcinoma in the radical prostatectomy (RP).
Design: 3 cases were identified from the consult files of one of the authors.
Results: Prostatic biopsies from 3 patients showed foci of conventional and "small cell HGPIN" (including foci that would be regarded as IDC-P). 2 cases were associated with separate foci of acinar adenocarcinoma in other cores (Gleason scores 3+4 and 4+4 in 1 case; 3+3 in 1 case). Small and large-caliber ducts with small cell-like change typically showed cribriform proliferations of atypical cells with abrupt transition between centrally located small cells with large more typical HGPIN cells located at the duct periphery. “Small cell” areas showed crowded cells with uniformly bland vesicular nuclei and scant cytoplasm. Despite a “small cell appearance” at low magnification, no apoptotic bodies or mitotic figures were seen in the “small cell” areas. Immunostaining in 2 cases showed negative staining in the small cell population for NSE, chromogranin, and synaptophysin. Racemase was positive only in the large HGPIN cells in 1 case, although the other case showed positivity in both "small cell" and typical large HGPIN cell populations. The MIB-1 proliferation index varied from 0 – 10% with predominant labelling of larger HGPIN cells and minimal reactivity in the small cell population. One case with a subsequent RP showed extensive “small cell HGPIN” in addition to a small organ confined Gleason Score 3+4=7 adenocarcinoma. Another patient with "small cell HGPIN" on biopsy was alive at 10 years follow-up which would be unexpected if he had small cell carcinoma.
Conclusions: In contrast to the original report, our cases of “small cell HGPIN" were not associated with small cell carcinoma and showed no immunohistochemical evidence of neuroendocrine differentiation. Analogous to small cell urothelial CIS in the bladder, “small cell HGPIN” likely represents a morphologic mimic rather than true neuroendocrine differentiation. It may represent an extreme form of cellular maturation which is commonly seen toward the center of ducts involved by HGPIN. In order that it not be confused with small cell carcinoma, we propose that it be designated as “small cell-like HGPIN” or "small cell-like IDC-P", depending on the architecture of the neoplastic glands.
Category: Genitourinary (including renal tumors)

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 170, Wednesday Afternoon

 

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