• WHO recognized variant subtype of prostatic adenocarcinoma
• Malignant monophasic or biphasic neoplasm including a spindle cell or pleomorphic sarcomatoid component
• Represents dedifferentiation from (usually high grade acinar) prostatic adenocarcinoma
• Clinical, histologic, immunophenotypic or molecular evidence of origin from prostatic adenocarcinoma

Contributed by Steven Christopher Smith, M.D., Ph.D.

Contributed by Steven Christopher Smith, M.D., Ph.D.

• Carcinomatous component
  • Pancytokeratins: AE1 / AE3, CAM5.2, OSCAR
  • EMA
  • PSA and PAP
    • If positive, only focally
    • May be lost even in carcinomatous component posttreatment
  • Prostein / NKX3.1, PSMA
    • Expression may be retained even if PSA / PSAP lost
  • ERG (may be positive in ERG rearranged carcinomas)
• Sarcomatoid component
  • Pancytokeratins: AE1 / AE3, CAM5.2, OSCAR
    • Usually focally positive in sarcomatoid spindle cell component
  • High molecular weight cytokeratins: CK903 / 34 beta E12 and CK5/6
    • May show greater positivity in spindle cell component than pancytokeratins in some cases
  • p63 (focally) in sarcomatoid component
  • Other mesenchymal makers:
    • SMA, MSA and caldesmon positive in some cases
    • Desmin, myogenin, MyoD1 in heterologous rhabdomyosaromatous elements
    • S100 in heterologous chondrosarcoma
• References: Am J Surg Pathol 2006;30:1316, Mod Pathol 2018;31:S133

• Prostatic stromal sarcoma:
  • Arises primarily from prostatic stroma
  • No admixed (or prior) adenocarcinomatous component
  • Lacks keratin, p63, prostate marker expression
  • Usually expresses CD34, progesterone receptor (PR)
  • Variable SMA, desmin positivity
• Prostatic leiomyosarcoma:
  • No admixed (or prior) adenocarcinomatous component
  • Usually more fascicular spindle cell growth
  • Elongated cells, eosinophilic cytoplasm, cigar shaped nuclei
  • Diffuse SMA, desmin positivity
  • Lacks keratin, p63, prostate marker expression
• Prostatic solitary fibrous tumor:
  • No admixed (or prior) adenocarcinomas component
  • More cytologically uniform tumor with small spindled to polygonal cells
  • Uniform, angulated or carrot shaped nuclei
  • Patternless architecture, staghorn thin walled vasculature
  • Diffuse expression of CD34 and STAT6
  • Lacks keratin, p63, prostate marker expression

• Med Oncol 2019;36:27, Cancer 1992;69:2676, Am J Clin Pathol 1989;92:131

An 81 year old man presents with an obstructing urethral mass and on CT scan imaging is shown to have recent development of a 6 cm obstructing mass arising from the prostate, compressing and displacing the urethra. Transurethral resection demonstrates a spindle cell tumor with brisk mitotic activity and nuclear pleomorphism but no prostatic or urothelial carcinoma is visible. What additional findings would argue most strongly for diagnosis of sarcomatoid carcinoma of the prostate?

1. Dense, fascicular growth, diffuse expression of desmin and SMA
2. Focal desmin positivity, diffuse vimentin positivity
3. Patchy high molecular weight keratin expression in subsets of the spindle cells, history of high grade prostatic adenocarcinoma treated by androgen deprivation therapy and pelvic radiotherapy 5 years previously
4. Staghorn vasculature, CD34 and STAT6 expression

C. Patchy high molecular weight keratin expression in subsets of the spindle cells, history of high grade prostatic adenocarcinoma treated by androgen deprivation therapy and pelvic radiotherapy 5 years previously

Comment Here

Reference: Sarcomatoid carcinoma

A 48 year old man presents with an obstructing mass arising in the prostate and bladder neck. It demonstrates dense, organized fascicular growth of fusiform cells with dense eosinophilic cytoplasm and elongated nuclei. What features would support consideration of a prostatic leiomyosarcoma?

1. Positive rearrangement of the ERG locus by FISH
2. Scattered admixed glands with cytoplasmic atypia; focal p63 and CK903 / 34 beta E12 expression in scattered spindle cells
3. Strong, diffuse expression of SMA and desmin
4. Thin walled ramifying vasculature, nuclear STAT6 positivity

C. Strong, diffuse expression of SMA and desmin

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Reference: Sarcomatoid carcinoma