Synovial sarcoma

Prostate
Other malignancies
Synovial sarcoma

Author: Kenneth A. Iczkowski, M.D.

Topic Completed: 1 March 2017

Revised: 28 February 2019

Copyright: 2003-2019, PathologyOutlines.com, Inc.

PubMed search: prostatic synovial sarcoma

Page views in 2018: 399

Page views in 2019 to date: 243

Table of Contents

Cite this page: Iczkowski KA. Synovial sarcoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/prostatesynovialsarcoma.html. Accessed October 14th, 2019.

Definition / general

Primary prostatic synovial sarcoma is a rare presentation of a well studied disease (see Soft tissue topic), and is one of the few primary sarcomas to occur in the prostate (Arch Pathol Lab Med 2017;141:301)

Essential features

Spindle and oval cells forming interlacing fascicles
Aggressive growth and metastasis common

Epidemiology

Age range of 28 to 63 years

Diagnosis

Reportedly established on a core needle biopsy in 1 case and transurethral resection of the prostate in a second; in 8 other cases, on resection

Case reports

22 year old man with metastatic tumor to liver and lung (World J Surg Oncol 2014;12:194)
37 year old man with monophasic tumor (Am J Surg Pathol 1999;23:220)
44 and 46 year old men (J Surg Pathol 2008;16:329)
Three cases, two with documented metastasis (Korean J Urol 2014;55:797)
Survival is documented in 3 cases (Histopathology 2006;48:321, Urology 2013;82:160)

Treatment

Combinations of surgical resection, chemotherapy or radiation therapy
Surgical procedures range from radical prostatectomy to pelvic extenteration with en bloc penectomy and pubectomy

Microscopic (histologic) description

Uniform spindle and oval cells forming interlacing fascicles resembling fibrosarcoma
Focally the compact fascicles of tumor cells alternate with hypocellular myxoid tissue resembling peripheral nerve sheath tumors
Focal pericytomatous pattern of polygonal cells arranged around dilated, thin walled blood vessels

Microscopic (histologic) images

Contributed by Kenneth Iczkowski, M.D.

A cellular pattern of overlapping uniform spindle
and oval cells forming interlacing fascicles is
evident in this needle biopsy. Pericytomatous
cell arrangement was not prominent

Positive stains

CK7, EMA, Bcl2, CD99, E cadherin and vimentin (most cells) (Arch Pathol Lab Med 2017;141:301)

Negative stains

S100, keratin, neuron specific enolase, CD34, desmin, muscle specific actin, alpha smooth muscle actin

Molecular / cytogenetics description

Has SYT-SSX gene fusion due to t(X;18)(p11.2;q11.2) (Int J Surg Pathol 2008;16:329)

Differential diagnosis

Other sarcomas reported in the prostate include, in descending order of incidence:
- Leiomyosarcoma
- Rhabdomyosarcoma
- Prostatic stromal sarcoma
- Malignant peripheral nerve sheath tumor
- Osteosarcoma
- And a few others
The above battery of immunostains should help establish the diagnosis

Board review question #1

Which of the following stains when positive helps confirm synovial sarcoma:

CD34
CD99
Cytokeratin 20
Desmin
Calretinin

Board review answer #1

B. CD99

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