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prostatic non-epithelial tumors

Monday 30 July 2012

Prostatic neoplasms of non-epithelial origin; mesenchymal tumours of the prostate; non-epithelial prostatic tumors

Prostatic neoplasms of non-epithelial origin are rare, representing only @<@1% of all prostatic tumours.

Although they are infrequent, they comprise a broad range of entities, both benign and malignant, and include both tumours specific to the prostate (i.e. specialized stromal tumours) and similar tumours occurring in extraprostatic sites [e.g. smooth muscle tumour, myofibroblastic tumour, solitary fibrous tumour (SFT), and gastrointestinal tumour (GIST)].

Most non-epithelial prostatic tumours are believed to arise from innate prostate and/or periprostatic mesenchymal elements (e.g. fibromuscular stroma, smooth muscle, blood vessels, paraganglia, and nerves) and from haematopoietic cells (e.g. lymphoma), but some are also derived from structures not normally present in the prostate, such as melanocytes (i.e. blue naevus, melanosis, and melanoma) and germ cells [e.g. seminoma and yolk sac tumour (YST)].

A subset may arise in extraprostatic soft tissue and involve the prostate (e.g. GIST, SFT, paraganglioma, and neural tumours), and in some tumours the exact cell of derivation is unknown.

Unlike for most prostate carcinomas, the diagnosis of non-epithelial neoplasms in the prostate always involves the question of whether the tumour is primary or secondary.

Because of their non-acinar origin, the serum prostate-specific antigen (PSA) level is typically not elevated, although it can be mildly increased or significantly high if concomitant adenocarcinoma is present, which may not be unusual in incidental low-grade or benign non-epithelial lesions.

The diagnosis is compounded by significant overlap in morphology of several entities, both prostatic and non-prostatic, particularly the broad category of spindle cell lesions, which also include epithelial tumours (e.g. sarcomatoid carcinoma) and non-neoplastic processes [e.g. benign prostatic hyperplasia (BPH)].

Accurate distinction is warranted because of stark differences in biological behaviour (e.g. inflammatory myofibroblastic tumour or hyperplasia versus sarcoma) and differing therapeutic implications (e.g. GIST) among several of the entities.

The diagnosis is also complicated by the fact that a significant number are often encountered in needle core biopsy samples, in which the limited amount of tissue sampled may not be sufficient for an accurate diagnosis to be made.

Types

- prostatic specialized stromal tumours

- prostatic smooth muscle tumour

  • prostatic leiomyoma
  • prostatic leiomyosarcoma

- prostatic inflammatory myofibroblastic tumor/prostatic pseudosarcomatous myofibroblastic proliferation
- prostatic solitary fibrous tumor
- prostatic gastrointestinal stromal tumour (prostatic GIST)
- prostatic paraganglioma (extra-adrenal pheochromocytoma)
- prostatic adult rhabdomyosarcoma
- prostatic synovial sarcoma
- prostatic tumors with neural differentiation
- prostatic primitive neuroectodermal tumor (prostatic PNET)
- prostatic malignant fibrous histiocytoma (prostatic MFH)
- prostatic vascular tumors
- prostatic osteogenic tumors
- prostatic chondrogenic tumors
- prostatic hematopoietic tumors

  • prostatic lymphomas
  • prostatic localization of leukemias

- prostatic melanocytic tumors
- prostatic germ cell tumors

References

- Non-epithelial neoplasms of the prostate. Paner GP, Aron M, Hansel DE, Amin MB. Histopathology. 2012 Jan;60(1):166-86. PMID: 22212085