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Desmoplastic Small Cell Tumor

Definition

  • Keratin and desmin positive neoplasm composed of nests of small cells with surrounding desmoplastic stroma

Alternate / historical names

  • Desmoplastic small round cell tumor
  • Intraabdominal desmoplastic small round cell tumor
  • Small cell tumor with desmoplastic stroma

Diagnostic criteria

  • Nests and cords of cells surrounded by desmoplastic stroma
    • Stroma may occasionally be edematous
      • Rare cases may have scant stroma
    • May palisade at edge of nests
    • May exhibit central degeneration with discohesion or necrosis
    • Occasional tubular formation
      • May contain lumenal mucin
    • Occasional Homer-Wright rosettes
    • Large cystic spaces infrequent
  • Uniform cells, 15-20 microns diameter
    • Nuclei uniform, round to oval
      • Dense chromatin
      • Inconspicuous nucleoli
      • Pleomorphism may be induced by chemotherapy
    • Cytoplasm usually scant
      • May contain glycogen
      • May contain round paranuclear eosinophilic inclusions (rhabdoid)
      • Occasionally spindled
    • Mitotic figures frequent
  • Keratin and desmin positive

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting : January 27, 2005
Last update: 8/8/11

Supplemental studies

Immunohistology

  • Expression of keratin and desmin is practically definitional
    • Rare negative cases require genetic analysis for diagnosis
    • Keratin (CAM5.2) 90%
    • Keratin (AE1/3) 70%
    • Desmin 80-90%
EMA 88%
WT1 70-100%
Vimentin 85%
CD15 75%
CD57 50%
Chromogranin 10-15%
Synaptophysin 10-15%
S100 10-15%
Smooth muscle actin 10-15%
CD99 / MIC2 0-50%
Myoglobin 0-30%
INI pos
  • Negative: Myogenin, MyoD, GFAP, neurofilaments, CEA, HMB45, AFP, CK5/6, CK20

Genetic analysis

  • t(11;22)(p13;q12) present in 95-100% of cases
    • Results in a chimeric EWS-WT1 fusion product
  • Rare other translocations identified

Differential Diagnosis

Extrarenal Rhabdoid Tumor Desmoplastic Small Cell Tumor
No desmoplastic stroma Prominent desmoplastic stroma
Desmin negative Desmin positive
INI1 loss 85% INI1 expressed 100%
Median age 8-9 years Mean age 25 years
Various deletions, translocations involving 22q11 t(11;22)(p13;q12)
Both may be rhabdoid and express keratin

 

The small cell pattern of DSCT may be confused with rhabdomyosarcoma. Both are desmin positive.
Embryonal Rhabdomyosarcoma Desmoplastic Small Cell Tumor
No desmoplastic stroma Prominent desmoplastic stroma
Keratin variable, faint and focal Keratin 90% positive, prominent
EMA negative EMA 90% positive
WT1 rare, focal WT1 positive
Muscle actin positive 95% Muscle actin rare
Median age 7 years Mean age 25 years
No consistent genetic abnormality t(11;22)(p13;q12)

 

Sclerosing Rhabdomyosarcoma Desmoplastic Small Cell Tumor
Keratin 5-50% positive, focal, weak Keratin 90% positive, prominent
EMA negative EMA 90% positive
WT1(C) negative WT1(C) positive
Any age group Mean age 25 years
No consistent genetic abnormality t(11;22)(p13;q12)
Both are desmin positive with a prominent sclerotic/desmoplastic stroma

 

The small cell pattern of DSCT may be confused with PPNET
Peripheral Primitive Neuroectodermal Tumor Desmoplastic Small Cell Tumor
CD99 positive CD99 35%
WT1 negative WT1 positive
Desmin only in ectomesenchymoma variant Desmin positive
Keratin 5-15% Keratin positive
EMA negative EMA positive
No desmoplastic stroma Prominent desmoplastic stroma
Various translocations involving 22q12 (no translocations involving 11p13) t(11;22)(p13;q12)

 

Carcinoma may simulate DSCT but is desmin negative

Clinical

  • Age 3-54 years, mean 22-25
  • 5:1 male:female
  • Vast majority arise in peritoneal cavity
    • Occasional cases in tunica vaginalis
    • Rare cases in pleura and lung
    • Very rare cases ethmoid sinus, scalp, kidney and pancreas
  • Usually presents with studding of peritoneal surface
  • Very poor prognosis

Grading / Staging / Report

According to the guidelines of the ADASP, desmoplastic small cell tumor is definitionally high grade

Use TNM Staging

The surgical pathology report should contain or address the following:

  • Location
  • Type of resection or biopsy
  • Histologic diagnosis
  • Managerial category IV (widespread disease assumed to be present at outset)
  • Grade: definitionally high grade
  • Stage
  • Size
  • Depth (dermis, subcutis, below fascia, body cavity)
  • Margins
    • Involved
    • Not involved
      • If under 2 cm give all such distances and sites
      • If over 2 cm give minimum distance and site
  • Results of supplementary studies if performed
  • Relationship to other specimens from the same patient

Lists

Small round blue cell tumors

Keratin positive soft tissue tumors (frequent and strong)

Bibliography

  • Kempson RL, Fletcher CDM, Evans HL, Henrickson MR, Sibley RS. Tumors of the Soft Tissues, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 30, 2001
  • Fletcher CDM, Unni KK, Mertens F. Pathology and Genetics of Tumours of Soft Tissue and Bone, World Health Organization Classification of Tumours 2002
  • Weiss SW, Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors, 4th edition, 2001
  • Hill DA, Pfeifer JD, Marley EF, Dehner LP, Humphrey PA, Zhu X, Swanson PE. WT1 staining reliably differentiates desmoplastic small round cell tumor from Ewing sarcoma/primitive neuroectodermal tumor. Am J Clin Pathol 2000 Sep;114(3):345-53
  • Barnoud R, Sabourin JC, Pasquier D, Ranchere D, Bailly C, Terrier-Lacombe MJ, Pasquier B. Immunohistochemical expression of WT1 by desmoplastic small round cell tumor: a comparative study with other small round cell tumors. Am J Surg Pathol 2000 Jun;24(6):830-6
  • Zhang PJ, Goldblum JR, Pawel BR, Fisher C, Pasha TL, Barr FG. Immunophenotype of desmoplastic small round cell tumors as detected in cases with EWS-WT1 gene fusion product. Mod Pathol. 2003 Mar;16(3):229-35
  • Lae ME, Roche PC, Jin L, Lloyd RV, Nascimento AG. Desmoplastic small round cell tumor: a clinicopathologic, immunohistochemical, and molecular study of 32 tumors. Am J Surg Pathol. 2002 Jul;26(7):823-35.
 
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