Microscopic description:

Microscopic images demonstrate myxomatous stroma with scattered, small, round, and blue malignant cells.

The histology of rhabdomyosarcoma is described as small blue round cell tumor, like microscopic descriptions of other malignancies such as neuroblastoma, Ewing’s tumors, neuroectodermal tumors, and lymphoma. To distinguish RMS from other small blue round cell malignancies is to use immunohistochemical staining for muscle markers such as a-actin, myoD, myogenin, and desmin (2).

Ancillary testing:
  • Positive: SMA, desmin, myogenic D (patchy).
  • Negative: CK7, GATA3, p63, SOX10, CD31, SMMS, ERG, H-CALDESMIN, PSA, NKX3.1

Discussion:

The bladder is the most common site of cancer in the genitourinary system with bladder cancer being the fourth leading cause of cancer death in males (behind lung, prostate, and colon). Urothelial transitional cell carcinoma is the most common form comprising more than 90% of cases in the US, next is squamous cell carcinoma (5%), adenocarcinoma (1%), and then the rarer forms of cancer found in the bladder – small cell carcinoma, bladder pheochromocytoma, bladder lymphoma and rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is most commonly described in children and adolescents, but extremely rare in adults. Rhabdomyosarcoma is the most common soft tissue tumor in children with 15-20% arising from the genitourinary tract (1). RMS tumors arise from the same embryonic mesenchyme as striated skeletal muscle but can also develop in other tissue such as fat, nerves, vessels, or skin. These tumors tend to be associated with pediatric conditions such as tuberous sclerosis, neurofibromatosis and Beckwith-Wiedmannn syndrome.

The two more common subtypes of RMS described in the literature, embryonic RMS and alveolar RMS affect the pediatric population and has had an overall improvement in survival in recent decades (2). Pleomorphic RMS is the subtype that tends to affect adults and its biology and genetics is not well understood. Since RMS is such a rare disease, the risk factors are poorly understood and there is no standardized treatment guideline. Adult patients with polymorphic RMS have a poor prognosis (2).

Lymph node involvement is an important factor in staging rhabdomyosarcoma since it has an impact on therapy and prognosis.

Historically treatment focused on early radical surgical excision. Little is known about which chemotherapy options work best for pleomorphic RMS but studies have tried combinations that include cyclophosphamide, doxorubicin, vincristine, ifosfamide, and dacarbazine.

Radiation therapy can be an option after chemotherapy or residual tumor in patient with incomplete surgical resection or positive lymph node involvement.

References:

Kieran K, and Shnorhavorian M. Current standards of care in bladder and prostate rhabdomyosarcoma. Urol Oncol. 2016 Feb; 34(2): 93-102.

Ruiz-Mesa C, Goldberg JM, Corondado Munoz AJ, Dumont SN, Trent JC. Rhabdomyosarcoma in Adults: New Perspectives on Therapy. Curr Treat Options in Oncol. 2015; 16 (6): 27

Rao MS, and Radhakrishan VV. Rhabdomyosarcoma of the urinary bladder in an adult – a case report. Indian J cancer. 1973 Dec; 10(4): 463-467.

Aggarwal A, Singh V, Pandey S, Sinha RJ. Embryonal rhabdomyosarcoma of urinary bladder in an adult patient: an unusual manifestation. BMJ Case Rep. 2018

Hellstrom HR, Fisher ER. Embryonal rhabdsomyosarcoma of the bladder in the ages. J Urol. 1961; 86: 336–9.

Evans AT and Bell TE. Thabdomyosarcoma of the bladder in adult patients: report of three cases. J Urol. 1965;94:573–5.

Krumerman MS, Katatikarn V. Thabdomyosarcoma of the urinary bladder with intraepithelial spread in an adult. Arch Pathol Lab Med. 1976; 100: 395–7.

Lloyd RV, Hajdu SI, Knapper WH. Embryonal rhabdomyosarcoma in adults. Cancer. 1983; 51: 557–65.

Kerr KM, Grigor KM, Tolley Da. Rhabdomyosarcoma of the adult urinary bladder after radiotherapy for carcinoma. Clin Oncol. 1989; 1: 115–6.

Lauro S, Lalle M, Scucchi L, et al. Rhabdomyosarcoma of the urinary bladder in an elderly patient. Anticancer Res. 1995; 15: 627–9.

Saltzman A and Cost NG. Current treatment of pediatric bladder and prostate rhabdomyosarcoma. Pediatric Urology. 2018 Feb; 19: 11.

CASE IMAGES