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Table of Contents
Definition / general | Essential features | Epidemiology | Clinical features | Diagnosis | Case reports | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Differential diagnosis | Additional references | Board review question #1 | Board review answer #1Cite this page: Iczkowski, K.A. Stromal tumor of uncertain malignant potential (STUMP). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/prostatestromalprolif.html. Accessed January 21st, 2019.
Definition / general
- Stromal neoplasms that involve only the prostate are divided into stromal tumor of uncertain malignant potential (STUMP), stromal sarcoma and carcinosarcoma
- STUMP, prior to 1998, was termed atypical stromal hyperplasia (Am J Surg Pathol 1998;22:148)
Essential features
- Rare prostatic tumors with stromal degenerative atypia featuring vacuolated nuclei
- Some resemble breast phyllodes tumors
- May recur rapidly after resection; rarely progress to stromal sarcoma
Epidemiology
- STUMP occurs in a broad age range with median age of 58 years (Am J Surg Pathol 1998;22:148, J Urol 2004;172:894)
Clinical features
- Usually presents with urinary obstruction, followed by hematuria, hematospermia and rectal fullness
- Many STUMPs are incidental findings and behave indolently
- A minority recur after surgery or metastasize
- Up to 46% reportedly recur without definitive surgery (Am J Surg Pathol 1998;22:148)
Diagnosis
- Microscopically, STUMP should have rare to no mitotic activity and lack necrosis
- Atypical stromal cells insinuate between benign acini
- CD34 and cytokeratin are the most helpful immunostains
Case reports
- 34 year old man with prostatic stromal tumor with fatal outcome (Rare Tumors 2010;2:e57)
- 56 year old man with recurrent prostatic stromal tumour of uncertain malignant potential (Ann Acad Med Singapore 2005;34:441)
- 59 year old man with a PSA of 7.9 (Case of the Week #269)
- 67 year old man with incidental prostatic stromal tumor of uncertain malignant potential (Urologia 2012;79:65)
Gross images
Images hosted on PathOut server:
Case of the Week #269
Images hosted on other servers:
STUMP which eventually metastasized
Microscopic (histologic) description
- Four patterns of STUMP have been described (J Urol 2004;172:894, Am J Surg Pathol 2006;30:694), all with degenerative / smudged chromatin:
- Hypercellular stroma with scattered degenerative atypia featuring vacuolated nuclei and smudged chromatin (50% of cases) (Fig. 1)
- Hypercellular stroma with bland spindle stromal cells
- Benign phyllodes-like, similar to breast, with "leaf like" growth of hypocellular fibrous stroma surfaced by benign prostate epithelium
- Myxoid stroma with bland cells, lacking the nodularity seen in benign hyperplasia (Am J Surg Pathol 1998;22:148, Am J Surg Pathol 2006;30:694)
- STUMP may also have epithelial proliferations which mask its diagnosis: most commonly glandular crowding, prominent basal cell layer, prominent papillary infolding (Am J Surg Pathol 2011;35:898)
- STUMP arises from specialized, hormonally responsive prostatic stromal cells, thus hormonal receptor immunostains may be positive
Microscopic (histologic) images
Images hosted on PathOut server:
Images contributed by Kenneth Iczkowski, M.D.
Fig. 1: STUMP, in a
prostate biopsy that
had cancer in other
fields
Case of the Week #269:
Fig. 4: Hypercellular stroma
Fig. 5: Circumscription of nodule
Fig. 6: Multinucleation
Fig. 7: Degenerative atypia
Fig. 8: STUMP positive for CD34
Fig. 9: STUMP positive for desmin
Fig. 10: STUMP positive for HHF35
Fig. 11: STUMP with low index for Ki67
Fig. 12: STUMP positive for progesterone receptor
Images hosted on other servers:
STUMP which eventually metastasized
Various images
Positive stains
- Only a few immunostains are discriminatory for STUMP; others are not helpful:
- CD34 and vimentin are most often positive (CD34 positivity helps rule out smooth muscle proliferations)
- Optional immunostains are progesterone receptor and androgen receptor, which should be positive (Prostate 1990;16:245, Arch Pathol Lab Med 2008;132:1729)
- Variable staining for smooth muscle actin and desmin (J Urol 2004;172:894, Am J Surg Pathol 2006;30:694)
Negative stains
- STUMP should be cytokeratin negative, ruling out sarcomatoid carcinoma
Differential diagnosis
- Carcinosarcoma: has malignant epithelial (CK+) and stromal components
- Sarcomatoid carcinoma: malignant stroma cells; epithelial cells are ERG+ (Histopathology 2015;66:898)
- Stromal nodule of nodular hyperplasia / benign prostatic hyperplasia: hyperplastic, not atypical stromal cells
Additional references
Board review question #1
- Expected features of STUMP include:
- CD34 is negative
- Cytokeratin positivity
- Degenerative nuclear atypia with nuclear vacuolation
- Does not tend to recur after resection necrosis
- Necrosis
Board review answer #1
C. Degenerative nuclear atypia with nuclear vacuolation is common to all four patterns of STUMP.
A. CD34 should be positive, ruling out smooth muscle tumor.
B. Cytokeratin positivity should prompt consideration of sarcomatoid carcinoma.
D. There is a tendency to recur after resection, so a prior diagnosis of STUMP is important.
E. Necrosis is a more malignant feature and probably rules out STUMP.
A. CD34 should be positive, ruling out smooth muscle tumor.
B. Cytokeratin positivity should prompt consideration of sarcomatoid carcinoma.
D. There is a tendency to recur after resection, so a prior diagnosis of STUMP is important.
E. Necrosis is a more malignant feature and probably rules out STUMP.
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