Prostate sarcoma

Case contributed by A.Prof Frank Gaillard

Presentation

Urinary symptoms.

Patient Data

Age: 35
Gender: Male
Modality: CT

CT scan demonstrates a large heterogenous mass seemingly arising from the prostate with evidence of invasion into the bladder, seminal vesicles and periprostatic soft tissues. 

Numerous hepatic and pulmonary metastases are present. 

Case Discussion

Histology

Microscopic description

Tissue shows  in areas  unremarkable surface  epithelium  comprising urothelium.   Most  of the tissue  shows a malignant   spindle  cell tumour   comprising   fascicles  of   moderately pleomorphic spindle cells with ovoid  nuclei.  There are frequent apoptotic bodies and mitosis are plentiful  (approximately 12 per 10 high power field).  There are areas of necrosis.  Some of the tumour  shows focal myxoid areas. There is no definite  skeletal  or smooth  muscle  differentiation,  nor  is there a heterologous component.   There is no malignant  epithelial component.  The tumour   infiltrates  into  bundles  of  smooth  muscle  presumably muscularis propria (detrusor).  There are also foci of lymphovascular space invasion.

The neoplastic cells show  diffuse strong staining  with vimentin. They are negative  for a  panel of  cytokeratin  stains  (AE1/3,  PAN and EMA), PSA (prostate specific  antigen), muscle  markers dermisn, smooth muscle actin (SMA) and caldesmon and melanoma  markers gp-100 and Mel-A. There is focal, weak equivocal staining  of some cells with S-100,  and the significance of this is uncertain.

The morphology is of a  malignant sarcomatoid  neoplasm, and in view of the negative keratin staining,  it is most likely a  sarcoma.

The differential diagnosis (which hasn't been entirely excluded) includes a monomorphic synovial  sarcoma for which cytogenetic  studies to demonstrate the diagnostic translocation  t(X;18) will  be necessary.   A spindle cell rhabdomyosarcoma has been considered in the differential diagnosis but this is considered less likely as most of  these tumours are desmin-positive and there are morphologically identifieable rhabdomyoblasts (which are not seen in this case).

Final diagnosis

Transurethral  biopsies - high grade  sarcoma with  lymphvascular invasion, morphology initially suggesting a synovial sarcoma. FISH studies are  NEGATIVE for SYT (18q11.2) breakapart signals however. 
(X;18) translocation associated with synovial sarcoma NOT detected. 

In view of the negative  FISH study, this tumour  is best considered a high grade sarcoma, NOS.

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Case Information

rID: 11028
Case created: 10th Oct 2010
Last edited: 17th Nov 2015
System: Urogenital
Inclusion in quiz mode: Included

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