Paratesticular alveolar rhabdomyosarcoma

Case contributed by Dr Yair Glick


Painless left scrotal mass.

Patient Data

Age: 17 years
Gender: Male

Firm mass measuring ~4.5 x 2.7 x 2.0 cm with heterogeneous echotexture and internal flow in the entrance to the left inguinal canal, appearing inseparable from the spermatic cord. Left-sided grade 2 varicocele (not shown).

CT abdomen (no pathological finding in CT chest; not shown): staging for paratesticular mass

  • small left paratesticular solid mass, as also shown on ultrasonogram, displaying irregular borders and both peripheral and internal enhancement
  • heterogeneous mass measuring ~4.2 x 3.8 x 8.2 cm with peripheral enhancement, occupying the left ischiorectal fossa and extending anteriorly along the penile left corpus cavernosum, posteriorly to gluteus maximus, laterally to inferior pubic ramus, and crossing the midline
  • left internal iliac lymph node measuring 2.7 cm short axis with peripheral enhancement
  • left adrenal solid mass measuring 3.2 x 1.9 x 1.9 cm

In conclusion:
Left paratesticular mass with local extension as a left ischiorectal fossa mass, regional lymph node spread to left internal iliac chain and a distant metastasis to left adrenal.

    Case Discussion

    During physical check-up, preceding military conscription, the physician palpated a painless left scrotal mass. The patient was sent to the ER for further investigation.

    Following the US and CT studies shown above, the paratesticular mass was resected and sent to pathology.

    Left groin, CNB: Cores of fibrous tissue intermixed with sheets and nests of atypical small blue round cells, divided by thick fibrous septa. No necrosis identified.
    On immunostains the malignant cells are positive for myogenin and in part for desmin, and they are negative for CD20, CD3, EMA, synaptophysin, chromogranin, S100, myoglobin, MNF116, NSE, CD99, SMA and Fli1.
    The morphological features together with the results of immunostains and fluorescence in situ hybridization (FISH) examination are consistent with alveolar rhabdomyosarcoma.

    FISH: Vysis probe LSI FOXO1 (13q14) dual color break-apart rearrangement probe was used in order to detect translocation involving the chromosome 13 at the FOXO1 gene associated with alveolar rhabdomyosarcoma. 150 cells were evaluated.
    Result: 75% of the cells with rearrangement of the FOXO1 gene were seen.
    Cytocell dual color break-apart rearrangement probes PAX3 (2q35) and PAX7 (1p36) were used in order to detect translocation of these genes associated with alveolar rhabdomyosarcoma. 50 and 60 cells were scored, respectively.
    Result: 75% of the cells showed translocation of the PAX3 gene. No cell showed translocation of the PAX7 gene.
    Vysis probe LSI EWSR1 (22q12 Ewing sarcoma) dual color break-apart rearrangement probe was used in order to detect translocation of Ewing gene. 100 cells were evaluated.
    Result: No cells with rearrangement of the Ewing gene were seen.

    The patient underwent 18FDG PET/CT that showed additional metastases in thoracic vertebrae and both femora.

    In summary: Metastatic paratesticular alveolar rhabdomyosarcoma with chromosome 13 translocation, which sadly carries a dismal prognosis.


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