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13 March 2013 - Case of the Week #269
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Thanks to Dr. Debra L. Zynger and Joshua J. Ebel, BS, The Ohio State University Medical Center, for contributing this case and the discussion. To contribute a Case of the Week, follow the guidelines on our Case of the Week page.
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Case of the Week #269
A 59 year old man with a PSA of 7.9 had a prostatic needle biopsy, followed by a prostatectomy:
What is your diagnosis?
Stromal Tumor of Uncertain Malignant Potential (STUMP)
The initial needle core biopsy demonstrated STUMP. Prostatectomy showed STUMP diffusely involving the prostate with a minimal amount of prostatic adenocarcinoma (Gleason 3+3=6, 2% of the gland). The STUMP had degenerative atypia and phyllodes-like
Left to right: CD34, desmin, HHF35, Ki-67, PR
The STUMP was positive for CD34, desmin and PR with negative staining in the above image (variable staining elsewhere) and low staining for Ki-67.
STUMP are rare prostatic tumors characterized by atypical stromal proliferation, that may resemble breast phyllodes tumors (Am J Surg Pathol 1998;22:148, Mod Pathol 2007;20:148). They are characterized by hypercellular stroma or cytologic atypia, but without evidence of true sarcomatous transformation. The atypical stromal cells have enlarged nuclei with nuclear hyperchromasia and variable multinucleation. There are few/no mitotic figures, and no atypical mitotic figures. Tumors may be associated with benign prostatic glands that may including crowding, a prominent basal cell layer or prominent papillary infolding (Am J Surg Pathol 2011;35:898)
STUMP tumors have 4 histologic patterns:
However, these patterns are not associated with behavior.
- Hypercellular stroma with scattered cytologically atypical cells associated with benign glands
- Hypercellular stroma with minimal cytological atypia associated with benign glands
- Hypercellular stroma and benign glands in a "leaf like" growth pattern resembling breast phyllodes tumor, with variable cytologic atypia, or
- Hypercellular stroma without cytologically atypical stromal cells and without glands
The differential diagnosis includes stromal sarcoma (greater cellularity, mitoses, necrosis, and stromal overgrowth). Some authors consider phyllodes tumor to be a nonspecific pattern, and recommend using a diagnosis of either STUMP or stromal sarcoma
Treatment is somewhat controversial, because of the small number of cases studied, and because outcome varies from a benign course to recurrence and stromal sarcoma (Am J Surg Pathol 2006;30:694, eMedicine).
Nat Pernick, M.D., President
and Palak Thakore, Associate Medical Editor
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