Bladder - Rhabdomyosarcoma

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Other tumors

Rhabdomyosarcoma

Reviewers: Nat Pernick, M.D., PathologyOutlines.com, Inc. (see Reviewers page)
Revised: 30 June 2011, last major update June 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Definition
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● Sarcoma with features of skeletal muscle differentiation
● Either embryonal (botyroid or spindle cell), alveolar or pleomorphic rhabdomyosarcoma

Epidemiology
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● Less than 0.5% of all bladder tumors, but one of most common tumors of the lower urogenital tract in children
● Often children 2-6 years old; 75% male
● Adult tumors are usually alveolar or unclassified, commonly with anaplasia, and resemble small cell carcinoma (Am J Surg Pathol 2008;32:1022)

Botyroid variant:
● Occurs in mucosal lined, hollow cavities (vagina, nasal cavity, bladder); most common bladder tumor in children
● May be associated with Wilm’s tumor and Dandy-Walker syndrome

Sites
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● Usually in trigone
● Infiltrates adjacent tissue but distant metastases are rare

Etiology
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● Arise from primitive muscle cells

Clinical features
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● 5 year survival for embryonal subtype is 50-80% (BJU Int 2010;106:557, Pediatr Blood Cancer 2011;56:718)
● Adult tumors are uniformly aggressive

Prognostic factors
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● Favorable prognostic factors: children vs. adults, embryonal histology, low stage, polypoid (exophytic) growth pattern [10 year survival is 92% vs. 68% for diffuse intramural (endophytic) growth pattern]

Case reports
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● Antenatally diagnosed rhabdomyosarcoma of the bladder treated without extensive surgery (Nat Rev Urol 2009;6:449)
● 3-year-old girl with primary embryonal rhabdomyosarcoma (Arch Pathol Lab Med 2004;128:357)

Treatment
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● Surgery and chemotherapy
● Recurs if inadequately excised
● May die even after chemotherapy induced maturation (Am J Surg Pathol 2001;25:856)

Gross description
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● Mucoid, polypoid
● Botyroid tumors resemble a bunch of grapes

Gross images
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Botyroid type

Resembles bunch of grapes (courtesy of Dr. George M. Farrow, Rochester, MN)

Tumor nodules (arrows) along posterior wall

Tumor mass fills bladder lumen

Gray, glistening, gelatinous cut surface

Micro description
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● Myxomatous stroma with scattered, small, blue malignant cells, usually compressed beneath intact urothelium (“cambium layer”)
● Cross striations are often difficult to identify in untreated cases

Micro images
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Embryonal - botyroid type

Cambium layer overlies hypocellular, non-myxoid stroma

Polypoid projection of tumor into lumen, with cambium layer

Embryonal - spindle cell type

Uniform spindle cells in myxoid stroma with eosinophilic fibrillary cytoplasm and cigar shaped nuclei; image on right shows rhabdomyoblasts with abundant eosinophilic cytoplasm and variable cross striations

Figures 1/2: urine cytology shows primitive appearing round cells with minimal cytoplasm, lymphocyte-like nucleus with fine, evenly distributed chromatin and no nucleoli; nesting pattern in some areas (figure 2); Fig 3: biopsies show pleomorphic, round/oval and stellate cells infiltrating muscle wall and covered by intact urothelium; Fig 4: tumor cells are strongly desmin+

Positive stains
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● Muscle specific actin, desmin
● Myogenin and MyoD1 in well differentiated tumors

Negative stains
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● Myoglobin (usually), keratin (usually), calponin, h-caldesmon
● ALK1 (Mod Pathol 2007;20:592)

Molecular description
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● Alveolar subtype has translocations between #13 FKHR gene and either #2 - PAX3 or #1 - PAX7 gene
● Embryonal subtype has 11p-

Differential diagnosis
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● Carcinomas (urothelial or small cell) with rhabdomyosarcomatous differentiation: have distinct epithelial component

End of Bladder > Other tumors > Rhabdomyosarcoma

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