Testis & epididymis

Spermatic cord tumors


Topic Completed: 1 June 2014

Minor changes: 6 August 2021

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PubMed Search: Rhabdomyoma [title] spermatic cord

Swapnil U. Rane, M.D.
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Cite this page: Rane S. Rhabdomyoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/testisparatestrhabdo.html. Accessed December 3rd, 2021.
Definition / general
  • Rhabdomyomas are cardiac and extra-cardiac; both types do NOT appear in same patient
  • Cardiac rhabdomyomas are believed to be hamartomatous, have a strong association with tuberous sclerosis and often undergo spontaneous resolution
  • Extra-cardiac rhabdomyomas are believed to be neoplastic, although benign
    • Three types dependent on constituent cell type
      • Adult type: cells resemble mature adult skeletal muscle
      • Fetal type: mixture of small cells and fetal type skeletal muscle cells
      • Genital type: mixture of adult and fetal type cells
  • ~2% of skeletal muscle tumors
  • Most frequent extracardiac rhabdomyoma: adult type
  • Most frequent rhabdomyoma occurring in the genital region: genital type
  • Genital type of rhabdomyoma more common among women, most often reported in young adults in 2nd to 4th decade of life
  • Epididymis, prostrate, tunica, spermatic cord or paratesticular soft tissue
Clinical features
  • Slow growing, usually accidently discovered on routine examination
  • No specific laboratory features
  • Normal levels of serum tumor markers
Prognostic factors
  • Benign tumor with no potential for malignant transformation
  • Extracardiac adult type rhabdomyomas may recur (Hum Pathol 1993;24:608)
  • No reports of recurrence in paratesticular rhabdomyomas
Case reports
  • Surgical resection; no further treatment required
Gross description
  • Dense, fibrous tumor ranging from 2 - 5 cm
Microscopic (histologic) description
  • Cell type depends on type of rhabdomyoma
    • Adult type
      • Large polygonal cells with abundant eosinophilic cytoplasm embedded in dense fibrous stroma
      • Tumor cells have cytoplasmic cross striations on H&E, which are highlighted with PTAH stain
      • Low N:C ratio, round, small and bland nuclei without any mitosis
      • Cells may be vacuolated if rich in glycogen which is washed off during processing
      • Small amount of lipid demonstrable by Oil red-O is usually present
    • Fetal type: mixture of cells resembling small cells and fetal skeletal muscle cells
    • Juvenile type: intermediate between adult and fetal type
Microscopic (histologic) images

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Various images

Vimentin and desmin+

Positive stains
Negative stains
Electron microscopy description
  • Variable number of mitochondria with linear cristae and deposits of glycogen
  • Thin and thick myofilaments show a varying degree of differentiation and measure 50-70 nm and 135-150 nm in diameter, respectively
  • Distinct Z lines are readily discernible within the I band, but sometimes A, H, M, and N bands are also apparent
  • Triads: trigonal arrays of actin and myosin filaments can be seen in cross-section
Differential diagnosis
  • Granular cell tumour: no striations, diffusely S100+, negative for myogenin and other muscle markers
  • Hibernoma: diffusely S100+, negative for muscle markers, phagolysosomes seen on ultrastructure
  • Paraganglioma: mixture of ganglionic and sustentacular cells; no striations, characteristic vascular pattern, sustentacular cells are S100+, ganglion cells are NSE+, chromogranin+
  • Rhabdomyosarcoma: malignant small round blue cell tumor or spindle cell tumor; cambium layer present in embryonal rhabdomyosarcoma-botryoid variant; numerous mitoses, CD99+, skeletal muscle markers variably positive, high Ki67 index
  • Rhabdomyomatous mesenchymal hamartoma of skin: restricted to skin, common in children and in chin region; usually solitary; often admixed with mature adipose tissue, blood vessels and adnexal structures
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