Testis & epididymis

Spermatic cord tumors


Topic Completed: 1 July 2014

Minor changes: 16 November 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: Rhabdomyosarcoma [title] testis

Swapnil U. Rane, M.D.
Rafael Jimenez, M.D.
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Cite this page: Rane S., Jimenez, R. Rhabdomyosarcoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testisrms.html. Accessed December 7th, 2021.
Definition / general
  • Primitive malignant round cell tumor with skeletal muscle differentiation by immunohistochemistry or ultrastructure
  • Relatively rare, 7% of all rhabdomyosarcomas, 6% of all paratesticular tumors but still the most common nongerminal malignant tumor in the paratesticular region
  • Incidence: ~1/20 million males per year
  • Paratesticular region is the most common site for rhabdomyosarcomas in teenagers
  • No preference for either side or race has been demonstrated
  • Embryonal RMS (including its variant spindle cell type) is the most common subtype in this region, although any subtype can occur
    • Embryonal RMS is also the most common childhood malignant tumor of spermatic cord
    • Occurs in all age groups but most common in children; peak age is 9 years
    • ~80% occur before age 21 years, 20% are equally distributed in older age groups
    • 80% overall survival
  • Alveolar RMS and pleomorphic RMS are less common, pleomorphic RMS is least common
    • Alveolar RMS occurs mainly in young adults and adolescents
    • Pleomorphic RMS occurs mainly in adults
  • Spindle cell RMS first described in 1992 by German-Italian Cooperative Sarcoma Study (Am J Surg Pathol 1992;16:229)
  • Most cases are centered around paratesticular soft tissue with variable testicular involvement
  • Commonly spreads through lymphatics to iliac lymph nodes but hematologic spread to lungs and liver also occurs
Clinical features
  • Short clinical history of painless swelling in scrotum of days to weeks duration is most common presentation
  • Pain or history of trauma is extremely uncommon (~7% cases for each)
  • Tumor is usually large at presentation, often reaching the inguinoscrotal region
  • 1/3 to 1/2 have metastases at presentation
  • Suspected clinically or by imaging, confirmed by histology
  • No specific laboratory features
  • Negative markers for germ cell and sex cord stromal tumors
  • Liver function tests may be affected by metastases
Radiology description
  • MRI reveals a heterogeneously enhancing, well defined soft tissue mass classically encasing or displacing the testis
Prognostic factors
  • Poor prognosis is related to:
    • Age of the patient ≥ 10 years or < 1 year
    • Site of origin: parameningeal, bladder, prostate, abdomen, trunk, extremities are associated with poor prognosis; orbital, paratesticular and vaginal locations are associated with better prognosis
    • Tumor size (largest diameter) > 5cm
    • Locally invasive (T2) tumor
    • Incomplete resectability
    • Presence of distant metastases at diagnosis
    • Number of metastatic sites or tissues involved
    • Presence of regional lymph node involvement (N1)
    • Histopathologic subtype: pleomorphic worse than alveolar, worse than embryonal (J Clin Oncol 2003;21:78)
  • Intergroup Rhabdomyosarcoma Study group's International Classification of Rhabdomyosarcomas (Cancer 1995;76:1073)
    • Group I (better prognosis): botyroid and spindle cell variants
    • Group II (intermediate prognosis): embryonal NOS
    • Group III (worse prognosis): alveolar
    • Group IV (unclear prognosis): RMS with rhabdoid features, embryonal RMS with anaplastic features, sclerosing RMS
Case reports
  • Multimodal approach of surgical excision, VAC based chemotherapy is standard of care
  • While most authors support use of chemotherapy, there is significant toxicity
  • Ferrari et al suggested that low risk cases receive low dose anthracycline free regimens without any loss of benefit
    • Their study of 216 cases of pediatric paratesticular rhabdomyosarcoma had overall 5 year survival of 85.5%, 95% for localized disease, 2% for metastatic disease (J Clin Oncol 2002;20:449)
  • Radiotherapy for local disease control may be given
  • Retroperitoneal lymph node dissection is not advocated unless there is evidence of lymph node enlargement / involvement by imaging
  • Detailed approaches and stratification for treatment are available (Expert Rev Anticancer Ther 2005;5:283, Sarcoma 2001;5:9, Clin Oncol (R Coll Radiol) 2013;25:27)
Clinical images

Images hosted on other servers:

Large epididymal mass

USG: ill defined heterogeneous mass

20 cm scrotal mass

Gross description
  • Encapsulated, lobulated, smooth, gray white glistening mass that displaces testicular parenchyma but typically does not invade testicular tissue
  • 1 to 20 cm, with foci of hemorrhage and cystic degeneration
  • Embryonal RMS: fleshy grayish white to pinkish tan mass, 4 - 6 cm and may be mucoid
  • Spindled RMS: mean 5.8 cm, median: 4.6 cm, similar to classical embryonal RMS (mean: 6.4 cm, median: 6 cm) as reported in the IRS I & II studies (Am J Surg Pathol 1993;17:221)
Gross images

Images hosted on other servers:

Scrotal mass

Yellow myxoid solid tumor

Displacing testis

Microscopic (histologic) description
  • Mixture of haphazardly arranged rhabdomyoblasts and undifferentiated primitive cells
  • Primitive cells are small and round with minimal cytoplasm, dark nuclei
  • Variable numbers of strap cells, with or without cross striations and bizarre "tadpole" cells
  • Variable mitotic activity
  • Embryonal RMS: small cells with hyperchromatic nuclei, minimal cytoplasm as well as cells with rims of eosinophilic cytoplasm and spindle cells with cytoplasmic tails and variable cross striations; myxoid or collagenous stroma
  • Spindled RMS:
    • Predominant cell type is elongated, spindle cell arranged in fascicles or whorls; herringbone growth pattern may be seen
    • Cells have eosinophilic fibrillar cytoplasm, centrally located nuclei with blunted or fusiform ends, small to inconspicuous or prominent nucleoli
    • Mitotic figures are easily appreciated, including atypical forms
    • A smaller proportion of admixed immature rhabdomyoblasts are usually seen, with bright cytoplasmic eosinophilia, eccentric nuclei and occasionally cytoplasmic cross striations (useful for diagnosis and to differentiate from leiomyosarcoma)
    • Variable collagen fibers intermingled between the spindle cells
    • Some authors, including the IRS I & II studies, identified collagen rich and collagen poor spindle cells
      • Collagen poor: cells are arranged in bundles or fascicles with abundant cellularity and little or no stroma, resembling leiomyosarcoma
      • Collagen rich: lower cellularity due to abundant fine collagen fibers with a "storiform" pattern giving it a more sclerotic appearance
      • This subclassification does not appear to affect clinical outcome
Microscopic (histologic) images

Case #145

Various images




AE1 / AE3

Images hosted on other servers:

Spindle shaped cells

H&E, desmin, MyoD1

Embryonal (3 images)


Cytology description
  • Spindle cell variant: mumerous spindle cells and large fragments of cytoplasmic processes with cross striations (Acta Cytol 2005;49:331)
Positive stains
  • Desmin, myoglobin, myosin, MSA (nonspecific)
  • MyoD1 (nuclear expression; regulatory protein in skeletal muscle differentiation) - confirmatory marker
  • Myogenin (nuclear expression; regulatory protein in skeletal muscle differentiation) - confirmatory marker
  • May rarely express cytokeratin
Negative stains
Electron microscopy description
  • Thin actin and thicker myosin filaments are seen
  • No neurosecretory granules
  • Spindled variant is more differentiated with higher proportion of cases expressing markers of mature muscles (myoglobin, troponin T and muscle specific actin) compared to nonspindle cell variants (Am J Surg Pathol 1993;17:221); the more mature nature of spindle cell RMS is also evident on ultrastruture, with a more uniform presence of thick and thin filaments within the spindle cells
Molecular / cytogenetics description
  • Partial monosomy of chromosome 11; loss of heterozygosity (LOH) at 11p characterizes embryonal RMS
    • LOH by loss of maternal copy and duplication of paternal copy of 11p results in activation of IGF2 (IGF2 is known to show genomic imprinting, with silencing of the maternal allele)
  • Alveolar RMS: characterized by t(2;13)(q35;q14) or t(1;13)(p36;q14), resulting in PAX3-FKHR or the PAX7-FKHR fusion proteins, detectable in 75 - 80% of alveolar RMS but absent in other subtypes; some cases have loss of imprinting of the IGF2 gene with re-expression of the normally silent maternal allele
  • Spindle cell RMS: PAX3-FKHR / PAX7-FKHR fusion (RMS1 / RMS2) associated with alveolar RMS are classically absent; cytogenetically, spindle cell RMS is close to embryonal RMS, based on presence of sporadic small gains of chromosome 2, 8, 11, 13 & 20
Differential diagnosis
  • Fibrosarcoma: herringbone pattern, may have similar morphology but no rhabdomyoblasts, negative for skeletal muscle markers
  • Infantile fibromatosis: deep location, fascicles of spindle cells, no cross striations and no undifferentiated cells
  • Leiomyosarcoma: usually high grade, cigar shaped nuclei, no rhabdomyoblasts, often positive for caldesmon and negative for myoglobin
  • Neuromuscular hamartoma of soft tissue: usually age < 2 years, affects brachial plexus or sciatic nerve, multinodular growth with connective tissue separating nodules, no rhabdomyoblasts, muscular component is positive for desmin and muscle specific actin and neural component is positive for S100
  • Rhabdomyoma: benign tumor of skeletal muscle differentiation, no rhabdomyoblasts, no pleomorphism, no necrosis
  • Other small round cell tumors: Extraosseous PNET / Ewings tumor, Lymphoblastic lymphoma
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