prostate stromal tumor
Sunday 19 February 2012
prostatic stromal proliferations of uncertain malignant potential (STUMP); STUMPs; prostate stromal tumor of uncertain malignant potential; stromal tumor of the prostate
Sarcomas and related proliferative lesions of specialized prostatic stroma are rare.
Lesions have been classified into prostatic stromal proliferations of uncertain malignant potential (STUMP) and prostatic stromal sarcoma based on the degree of stromal cellularity, presence of mitotic figures, necrosis, and stromal overgrowth.
There are several different patterns of STUMP, including: those that resemble benign phyllodes tumour; hypercellular stroma with scattered atypical yet degenerative cells; and extensive overgrowth of hypercellular stroma with the histology of a stromal nodule.
STUMPs are considered neoplastic, based on the observations that they may diffusely infiltrate the prostate gland and extend into adjacent tissues, and often recur.
Although most cases of STUMP do not behave in an aggressive fashion, occasional cases have been documented to recur rapidly after resection and a minority have progressed to stromal sarcoma.
STUMPs encompass a broad spectrum of lesions, a subset of which is focal as seen on simple prostatectomy, which neither recurs nor progresses, and could be termed in these situations as glandular-stromal or stromal nodule with atypia.
The appropriate treatment of STUMPs is unknown.
When these lesions are extensive or associated with a palpable mass definitive therapy may be considered.
Stromal sarcomas may have the overall glandular growth pattern of phyllodes tumours with obviously malignant stroma with increased cellularity, mitotic figures, and pleomorphism.
Other stromal sarcomas consist of sheets of hypercellular atypical stroma without the fascicular growth pattern of leiomyosarcomas.
The behaviour of stromal sarcomas is not well understood due to their rarity, although some cases have gone on to metastasize to distant sites.
Rare cases of adenocarcinoma of the prostate involving a phyllodes tumour have been identified.
Immunohistochemical results show that STUMP and stromal sarcomas both are typically positive for CD34 and may be used to distinguish them from other prostatic mesenchymal neoplasms, such as rhabdomyosarcoma and leiomyosarcoma.
Both STUMP and stromal sarcomas characteristically express progesterone receptors (PR) and uncommonly express estrogen receptors (ER), supporting the concept that STUMP and stromal sarcomas are lesions involving hormonally responsive prostatic mesenchymal cells, the specialized prostatic stroma.
STUMPS typically react positively with actin, whereas prostatic stromal sarcomas react negatively, suggesting that the expression of muscle markers in these lesions is a function of differentiation.