[898] Evaluation of the Epithelial Component of Stromal Tumor of Uncertain Malignant Potential (STUMP).

Michael Nagar, Jonathan Epstein. The Johns Hopkins Hospital, Baltimore, MD

Background: STUMPs are rare tumors characterized by an atypical, unique stromal proliferation of the prostate. Various stromal proliferations of STUMPs have been described (degenerative atypia, cellular stroma, phyllodes, myxoid stromal predominant), however, epithelial proliferations occurring within STUMP have not been systematically described to date.
Design: We reviewed 82 cases of STUMP from our consultation service from 1990 through 2010. 18 cases without a glandular component were excluded. We next evaluated the glandular component of the remaining 64 cases of STUMP for glandular crowding and complexity, prostatic intraepithelial neoplasia (PIN), squamous metaplasia, urothelial metaplasia, basal cell hyperplasia, adenosis, and clear cell cribriform hyperplasia.
Results: Of the 64 cases of STUMP, the stromal components were as follows, degenerative atypia N=39, cellular/spindled N=16, and phyllodes N=9. In 53 cases (83%), the glandular component differed from glands on the same biopsy specimen uninvolved by STUMP. The most common abnormalities were glandular crowding in 32/64 (50%) and a very prominent basal cell layer in some glands in 32/64 (50%) cases. The next most frequent glandular variation from normal was prominent papillary infolding in 13/64 (20%). Less frequent epithelial changes within the STUMP were as followed: 8/64 (12%) showed cystically dilated glands; 6/64 (9%) had urothelial metaplasia; 6/64 (9%) had basal cell hyperplasia; 5/64 (8%) showed squamous metaplasia; 3/64 (3%) had cribriform hyperplasia; 2/64 (3%) had adenosis; and 1 case each with high grade PIN and low grade PIN. The glandular component of STUMP was histologically normal in 11 (17%) cases. There was a tendency towards urothelial and squamous metaplasia in STUMPs with a phyllodes pattern, as well as a prominent basal cell layer in STUMPs with degenerative and cellular stroma.
Conclusions: This is the first study to systematically describe the epithelial proliferations occurring in STUMP. This study suggests that within STUMPs, there is epithelial mesenchymal crosstalk as has been described in benign prostate and in prostatic carcinogenesis. In unusual cases of STUMP, the epithelial proliferation was so predominant that it masked the diagnosis of STUMP.
Category: Genitourinary (including renal tumors)

Monday, February 28, 2011 1:00 PM

Poster Session II # 144, Monday Afternoon


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