Testis and epididymis
Paratesticular tumors
Desmoplastic small round cell tumor (DSRCT)

Author: Swapnil U. Rane, M.D. (see Authors page)
Editorial Board review: Debra Zynger, M.D.

Revised: 19 July 2017, last major update February 2015

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Desmoplastic small round cell tumor testis

Cite this page: Desmoplastic small round cell tumor. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/testisdesmoplasticsmall.html. Accessed October 22nd, 2017.
Definition / general
  • A malignant serosa related small round cell tumor with an epithelial growth pattern in a desmoplastic stroma
  • First described by Gerald and Rosai in 1989 (Pediatr Pathol 1989;9:177)
  • Highly aggressive, commonly multifocal, spreads along serosal surface
  • Rarely involves the testicular / paratesticular region and if affected, may represent spread from an intraabdominal tumor
Epidemiology
  • Predilection for young men in 2nd and 3rd decade
  • More common in adolescent and young adult males
  • Within the testicular / paratesticular region has an age range of 17 - 43 years (Am J Surg Pathol 1997;21:219)
  • Uncommon in women (M:F about 5:1)
Sites
Etiology and pathophysiology
Clinical features
  • Patients with localized paratesticular DSRCT present with scrotal mass, swelling and hydrocele, with variable pain
  • May present with more generalized symptoms like nonspecific abdominal pain, chest pain, effusions associated with DSRCT elsewhere
  • Aggressive with intraabdominal spread, nodal and pulmonary metastases
  • ~80% have metastatic disease at presentation; most common site is liver, also lungs, regional lymph nodes, mediastinal and neck nodes
  • 5 year survival postdiagnosis is < 20% (Am J Surg Pathol 1997;21:219)
Laboratory
  • CA125 or LDH may be useful to monitor response to treatment in cases with extensive peritoneal disease
Radiology images

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CT: large hyperdense right testicular mass

Ultrasound: right testicular mass

Prognostic factors
  • Localized disease has better prognosis
  • Primary extra-abdominal disease tends to be more localized - patients with paratesticular tumors have less disseminated disease
  • Extra-abdominal metastases confer poor prognosis
  • No validated staging system in practice (using TNM staging for soft tissue sarcomas, most cases would be stage IV)
  • Some centers use peritoneal carcinomatosis staging system (peritoneal cancer index - PCI) (Int Semin Surg Oncol 2005;2:3; J Pediatr Surg 2010;45:1000)
Treatment
  • Multimodality therapy is essential with aggressive surgery, multi-agent chemotherapy and radiotherapy
    • Surgical resection if operable disease
    • Neoadjuvant chemotherapy followed by surgical resection in disease not amenable to primary surgery
    • Surgical exploration is essential even in absence of radiologically evident disease after neoadjuvant therapy (Pediatr Blood Cancer 2007;49:274) as response to chemotherapy is rarely durable
    • Residual disease often present at surgical exploration, even if in radiological remission, due to low sensitivity of imaging techniques (MRI better than CT)
    • Long term response rates are proportional to the extent of surgical resection
  • Hyperthermic intraperitoneal perfusion (HIPEC) may have some benefit (J Pediatr Surg 2010;45:1000)
    • In a recent review, 3 year survival of 71% was reported in patients treated with HIPEC with surgery with or without chemotherapy vs 63% of patients with surgery with or without chemotherapy vs 26% in patients treated with only chemotherapy (Sarcoma 2012;2012:714986)
  • Although have elevated expression of PDGFRA, clinical trials of PDGFR inhibitors have been contradictory and not clearly shown to be of benefit (Cancer Chemother Pharmacol 2004;53:482, Pediatr Blood Cancer 2008;50:254)
Gross description
  • Firm, often multiple nodules, from a few millimeters to 10 cm
  • Closely related to tunica / serosal surface
  • Cut surface is usually grey, white, tan
Gross images

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Testis



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Solid, firm, grey white

Microscopic (histologic) description
  • Nests and anastomosing cords of uniform appearing small blue cells within desmoplastic stroma, sometimes with tubules and pseudorosettes
  • Scant eosinophilic cytoplasm with prominent cell borders
  • Nuclei are round, oval or elongated or grooved with finely dispersed chromatin and one or two small nucleoli
  • Mitoses are frequent, with abnormal mitotic figures
  • Single cell necrosis and comedonecrosis are common
  • Occasionally metaplastic changes with tubule formation, squamous metaplasia and glandular metaplasia with intracellular and extracellular mucin, may have signet ring cell change
  • Tumors may show rhabdomyoblastic differentiation with myoD1 positivity after chemotherapy
Microscopic (histologic) images

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Nests of cells with
scant cytoplasm in
desmoplastic stroma



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Nests of cells with
scant cytoplasm in
desmoplastic stroma

Round to oval nuclei

Well defined nests of small round blue cells

Peritoneal nodule

CK, vimentin, desmin and CAM5.2

Desmin+

Cytology description
  • Highly cellular smears with small round cells scattered singly and in small clusters
  • Scanty pale blue cytoplasm, may be vacuolated and show cytoplasmic densities
  • High N/C ratio, nuclear molding, variably smooth to irregular nuclear membranes, inconspicuous nucleoli, granular chromatin
  • Pseudorosettes may be seen
  • Stromal fragments may be seen in conventional smears but are uncommon on ThinPrep® preparations
  • Cytological examination alone does not facilitate differentiation from other small round cell tumors unless coupled with immunocytochemistry and genetic testing (Cancer 2002;96:21)
Cytology images

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Rosette-like features

Effusion has high cellularity

WT1+

Positive stains
  • Epithelial: keratin ( > 90% cases positive with most cytokeratin cocktails), EMA (more sensitive than cytokeratin), MOC31 / BerEP4 (70 - 100%)
  • Mesenchymal: vimentin, desmin (dot pattern of reactivity)
  • Neural: NSE, CD57
  • WT1 in > 90%
  • CA125 in 40%
  • NB84 (neuroblastoma marker) in 50%
Negative stains
Electron microscopy description
  • Neoplastic cells within nests lay in close apposition and are surrounded by a thin basal lamina
  • Poorly developed cell junctions
  • Dendritic like cell processes, dense core granules and neurosecretory granules may be seen, commonly in cases with neural marker positivity
  • Juxtanuclear aggregates of intermediate filaments, sometimes in globular whorls, correspond to dot-like positivity seen with desmin
  • Glycogen, lipid may be prominent in some cases
  • Signet ring cells with intracytoplasmic lumina as well as intercellular lumina may be seen (Am J Surg Pathol 1998;22:1314)
  • Microfilaments with densities of Z band-like material suggestive of either smooth or skeletal muscle differentiation are absent
Molecular / cytogenetics description
Molecular / cytogenetics images

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EWS-WT1 fusion transcripts

COBRA FISH karyogram

Differential diagnosis