Arch Pathol Lab Med—Vol 130, October 2006Rhabdomyosarcomas—Parham & Ellison
Rhabdomyosarcomas in Adults and Children
David M. Parham, MD; Dale A. Ellison, MD
● Context.—Rhabdomyosarcomas comprise a relatively
common diagnostic entity among childhood cancers and a
relatively rare one among adult tumors. They may possess
a variety of histologies that generally differ among age
groups. These lesions appear to be separate biologic enti-
ties as well as morphologic categories, with embryonal tu-
mors having genetic lesions related to loss of heterozygos-
ity and aberrant parental imprinting, alveolar tumors con-
taining genetic fusions between PAX and forkhead genes,
and pleomorphic tumors showing an accumulation of ge-
netic lesions similar to other adult high-grade sarcomas.
Objective.—To present guidelines for diagnosis of rhab-
domyosarcoma and recent finding concerning the biology
and classification of these lesions.
Data Sources.—Review of recent and older published lit-
erature and distillation of the authors’ experience.
Conclusions.—Infants and young children tend to have
embryonal rhabdomyosarcomas, adolescents and young
adults tend to have alveolar rhabdomyosarcomas, and old-
er adults tend to have pleomorphic rhabdomyosarcomas,
although there is some overlap. Newer rare entities, in-
cluding spindle cell rhabdomyosarcoma and sclerosing
rhabdomyosarcoma, have been described in children and
adults. Fusion-positive tumors have a distinct molecular
signature with downstream activation of a number of myo-
genic and tumorigenic factors. Genetic testing may be suc-
cessfully used for diagnosis and may guide therapy in fu-
ture clinical trials. Differential diagnosis has become sim-
pler than in previous years, because of use of myogenic
factors in immunohistochemistry, but classification based
solely on histologic features remains challenging.
(Arch Pathol Lab Med. 2006;130:1454–1465)
myogenesis, a well-defined biologic process that primarily
occurs during embryonal and fetal development.1As a re-
sult, these neoplasms tend to resemble stages of muscle
formation more akin to prenatal than postnatal life. This
often striking resemblance manifests not only by their his-
topathology but also by their pathobiology, as shown by
recent genetic studies of the tightly orchestrated process
of muscle development.1–4Thus, these tumors may be con-
sidered lesions that initiate myogenic differentiation but
fail to disconnect their constituent cells from the prolif-
erative cycle that terminal differentiation normally
Another unusual feature of rhabdomyosarcoma, per-
haps related to its linkage with somatic development, is
its propensity to affect children, primarily infants, tod-
dlers, and preschoolers.5,6Older children and adolescents
may also be affected, so that rhabdomyosarcomas com-
prise the most common single soft tissue sarcoma among
children and adolescents by a striking majority. On the
other hand, rhabdomyosarcomas are distinctly unusual in
habdomyosarcomas constitute a unique group of soft
tissue neoplasms that share a propensity to undergo
Accepted for publication March 9, 2006.
From the Departments of Pathology and Pediatrics (Dr Parham) and
Pathology (Dr Ellison), University of Arkansas for Medical Sciences and
Arkansas Children’s Hospital, Little Rock.
The authors have no relevant financial interest in the products or
companies described in this article.
Reprints: David M. Parham, MD, Arkansas Children’s Hospital De-
partment of Pathology, 800 Marshall St, Slot 820, Little Rock, AR 72202
adults,7who generally have tumors with pleomorphic,
high-grade cytologic features and differing biologic char-
A common misconception is that rhabdomyosarcomas
arise in skeletal muscle, but in fact many pediatric exam-
ples arise in viscera such as prostate, urinary bladder, and
gallbladder, which are devoid of striated muscle fibers.9,10
However, certain subtypes typically arise in the extremi-
ties and likely originate from myoblasts, particularly those
types associated with genetic fusions.11The exact origin of
extramyogenous rhabdomyosarcomas is more problemat-
ic, because myogenic transformation can be induced in
nonmuscle cells by genetic manipulation and might be re-
produced via tumorigenic influences.12,13Alternatively, or-
igin from misplaced myotomic cells cannot be completely
Another misconception is that rhabdomyosarcomas rep-
resent a single tumor type, whereas there are distinct clin-
ical, pathologic, and molecular differences among at least
3 different variants. These differences suggest that these
tumors comprise separate pathobiologic phenomena that
all share cellular and biologic features with developing
muscle. It is important to recognize these distinctions, for
they affect clinical outcome and approach to therapy.16
Rhabdomyosarcomas may arise from a wide variety of
locations.17These may be usefully separated into extrem-
ity and axial lesions, because the extremity tumors cause
local symptoms related to mass formation, infiltration,and
destruction of adjacent tissues. Axial tumors most com-
Arch Pathol Lab Med—Vol 130, October 2006 Rhabdomyosarcomas—Parham & Ellison
monly arise from the head and neck, the paraspinal re-
gion, and the genitourinary system, but tumors from other
abdominal and thoracic sites of origin occur. Among head
and neck lesions, orbital tumors occur most commonly.
Other sites include the nasal passages, paranasal sinuses,
mouth, pharynx, parotid region, temporal region, ptery-
goid region, and cheek. Rarely, intracranial meningeal tu-
mors can be seen.18Genitourinary tract lesions comprise
those affecting the urinary bladder, prostate, perineum,
vagina, cervix, uterus, and paratesticular soft tissues.
Paratesticular tumors are among the most common and
often affect older children and adolescents. Abdominal le-
sions include those of the retroperitoneum, abdominal
wall, and biliary tract. Thoracic tumors primarily affect the
chest wall. One must be particularly cautious with myo-
genic tumors of the lung and pleura, because these more
often represent pleuropulmonary blastomas than true
rhabdomyosarcomas. Rare tumors arise from the skin.19
As might be expected from their diversity of anatomic
sites, rhabdomyosarcomas have a host of clinical manifes-
tations. As a rule, these tumors present as bulging, infil-
trative, growing soft tissue masses that may be fungating
when they present in external locations such as the con-
junctiva and vagina. Obstructive features typically occur
with lesions of the genitourinary tract and biliary system,
causing urine or bile retention. Orbital lesions usually
cause proptosis and diplopia. Paraspinal tumors may have
neural manifestations if nerve roots are involved.
One striking feature of rhabdomyosarcomas is their as-
sociation with familial cancer syndromes. Initial studies
by Li and Fraumeni20on familial rhabdomyosarcoma led
to description of a cancer susceptibility syndrome later
proven to be caused by constitutional mutations of the
TP53 gene. This syndrome is characterized by a high risk
for early breast cancer, adrenal cortical neoplasia, gliomas,
hematopoietic cancers, and other bone and soft tissue sar-
comas. Independent observations by Beckwith21and Wie-
demann22lead to the recognition of a syndrome charac-
terized by somatic overgrowth and a propensity to devel-
op embryonal tumors including rhabdomyosarcoma, he-
patoblastoma, and Wilms tumor. Other features include
organomegaly, placentomegaly, macroglossia, omphalo-
cele, and adrenal cortical cytomegaly. The genetic study
of this disease has yielded a fascinating array of obser-
vations on the relation between tumor development and
nonmendelian genetics, as discussed later. The sarcoma-
tous tendencies of patients with neurofibromatosis 1 (NF1)
have long been recognized, and rhabdomyosarcomas are
along the list of tumors that have been described as af-
fecting them.23However, whether these are ‘‘true’’ rhab-
domyosarcomas or a variant of malignant triton tumors
has not been conclusively demonstrated. A subset of rhab-
domyosarcomas with patched gene mutations24,25appear
related to the syndrome described by Gorlin in patients
with heritable basal cell carcinoma, odontogenic kerato-
cysts, and medulloblastoma.
As may be surmised from the previous discussion, the
major histologic feature of rhabdomyosarcomas is their re-
semblance to developing muscle, but some may offer no
evidence of differentiation by routine stains and others
may show abundant differentiation and resemble rhab-
domyomas.26The key cell to recognize by routine micros-
copy is the rhabdomyoblast (Figure 1), a cell with an ec-
centric round nucleus and variable amounts of brightly
eosinophilic cytoplasm. Rhabdomyoblasts assume a vari-
ety of shapes that have been likened to straps, tadpoles,
tennis racquets, and spiders. Occasional tumors (less than
30%) contain terminally differentiated myoblasts with
cross striations. In our experience, these can be more easily
recognized by increasing the light intensity of the micro-
scope and lowering the condenser. More often, however,
the tumors are largely or entirely composed of undiffer-
entiated cells with round to oval nuclei with minimal cy-
toplasm and stellate borders. As they differentiate, rhab-
domyosarcoma cells undergo fusion, giant cell transfor-
mation, and tandem nuclear displacement, similar to nor-
mally developing myoblasts.
Of critical importance is recognition of the basic histo-
logic pattern, which separates rhabdomyosarcomas into
subtypes. Determination of the pattern may be difficult if
not impossible on limited biopsies, and one must also
carefully observe the cytologic features of the tumor cells.
The most common subtype, embryonal rhabdomyosarco-
ma, shows a loose and dense pattern created by variable
condensation of tumor cells, separated by a loose, myxoid
stroma often rich in connective tissue mucins (Figure 2).
This tumor must be separated from alveolar rhabdomyo-
sarcoma, which typically forms cellular nests separated by
fibrovascular septa (Figure 3). Alveolar rhabdomyosarco-
mas are highly cellular and often contain densely popu-
lated fields of small round blue cells. When this is the
predominant or sole feature (more likely seen in small
samples), then the term solid variant applies. Unfortunately,
this concept has engendered much confusion because of
the difficulties in separating solid foci of alveolar rhab-
domyosarcoma from the dense portion of embryonal
rhabdomyosarcoma. This becomes particular problematic
in embryonal tumors in which dense foci predominate.
Cytologically, embryonal rhabdomyosarcoma cells tend
to have oblong shapes with oval nuclei and relatively
bland chromatin, whereas alveolar rhabdomyosarcoma
cells tend to be larger and contain round, Ewing tumor-
like nuclei with central nucleoli and less cytoplasm. Solid
variants in particular may closely resemble nonHodgkin
lymphomas. Cytologic features may be helpful in sepa-
rating densely cellular embryonal rhabdomyosarcomas
from alveolar rhabdomyosarcomas, but one should not
hesitate to request additional studies such as molecular
genetics in problematic cases. It is not surprising that nu-
clear morphometry alone has been successfully used to
predict outcome in rhabdomyosarcoma.27
Ancillary studies are often critical with rhabdomyosar-
comas, because of the frequency of poorly differentiated
tumors. The diagnosis should be considered with all small
round cell neoplasms and an appropriate immunohisto-
chemical battery included in the workup. Fortunately,
muscle cells have a relatively unique phenotype, because
developing muscle expresses unique transcription factors
that initiate myogenesis. As a result, a small battery of 1
or 2 stains can be included in a larger workup and reveal
myogenic potential in virtually all appropriately fixed and
A large number of articles have touted various markers,
ranging from myasthenia gravis serum to dystrophin, as
potentially useful in diagnosis of myogenic tumors. In our
Arch Pathol Lab Med—Vol 130, October 2006Rhabdomyosarcomas—Parham & Ellison
coma in childhood: case report and review of the literature. Pediatr Dev Pathol.
81. Croes R, biec-Rychter M, Cokelaere K, De VR, Hagemeijer A, Sciot R.
Adult sclerosing rhabdomyosarcoma: cytogenetic link with embryonal rhabdo-
myosarcoma. Virchows Arch. 2005;446:64–67.
82. Deasy BM, Li Y, Huard J. Tissue engineering with muscle-derived stem
cells. Curr Opin Biotech. 2004;15:419–423.
83. Peng H, Huard J. Muscle-derived stem cells for musculoskeletal tissue re-
generation and repair. Transplant Immunol. 2004;12:311–319.
84. Li Y, Foster W, Deasy BM, et al. Transforming growth factor-beta1 induces
the differentiation of myogenic cells into fibrotic cells in injured skeletal muscle:
a key event in muscle fibrogenesis. Am J Pathol. 2004;164:1007–1019.
85. Barr FG, Galili N, Holick J, Biegel JA, Rovera G, Emmanuel BS. Rearrange-
ment of the PAX3 paired box gene in the paediatric solid tumour alveolar rhab-
domyosarcoma. Nat Genet. 1993;3:113–121.
86. Bois PR, Grosveld GC. FKHR (FOXO1a) is required for myotube fusion of
primary mouse myoblasts. EMBO J. 2003;22:1147–1157.
87. Xia SJ, Pressey JG, Barr FG. Molecular pathogenesis of rhabdomyosarco-
ma. Cancer Biol Ther. 2002;1:97–104.
88. Barber TD, Barber MC, Tomescu O, Barr FG, Ruben S, Friedman TB. Iden-
tification of target genes regulated by PAX3 and PAX3-FKHR in embryogenesis
and alveolar rhabdomyosarcoma. Genomics. 2002;79:278–284.
89. Khan J, Bittner ML, Saal LH, et al. cDNA microarrays detect activation of
a myogenic transcription program by the PAX3-FKHR fusion oncogene. Proc Natl
Acad Sci U S A. 1999;96:13264–13269.
90. Triche TJ. Tumor biology of soft tissue sarcoma: pathology and genetic
aspects [abstract]. Presented at: SMS 2005 International Sarcoma Meeting, June
15, 2005, Stuttgart.
91. Keller C, Arenkiel BR, Coffin CM, El-Bardeesy N, DePinho RA, Capecchi
MR. Alveolar rhabdomyosarcomas in conditional Pax3:Fkhr mice: cooperativity
of Ink4a/ARF and Trp53 loss of function. Genes Dev. 2004;18:2614–2626.
92. Knudson AG Jr, Strong LC. Mutation and cancer: a model for Wilms’ tumor
of the kidney. J Natl Cancer Inst. 1972;48:313–324.
93. Greaves MF, Wiemels J. Origins of chromosome translocations in child-
hood leukaemia. Nat Rev Cancer. 2003;3:639–649.
94. Xia SJ, Pressey JG, Barr FG. Molecular pathogenesis of rhabdomyosarco-
ma. Cancer Biol Ther. 2002;1:97–104.
95. Davis RJ, D’Cruz CM, Lovell MA, Biegel JA, Barr FG. Fusion of PAX7 to
FKHR by the variant t(1;13)(p36;q14) translocation in alveolar rhabdomyosarco-
ma. Cancer Res. 1994;54:2869–2872.
96. Sorensen PH, Lynch JC, Qualman SJ, et al. PAX3-FKHR and PAX7-FKHR
gene fusions are prognostic indicators in alveolar rhabdomyosarcoma: a report
from the Children’s Oncology Group. J Clin Oncol. 2002;20:2672–2679.
97. Fitzgerald JC, Scherr AM, Barr FG. Structural analysis of PAX7 rearrange-
ments in alveolar rhabdomyosarcoma. Cancer Genet Cytogenet. 2000;117:37–
98. Barr FG, Nauta LE, Davis RJ, Scha ¨fer BW, Nycum LM, Biegel JA. In vivo
amplification of the PAX3-FKHR and PAX7-FKHR fusion genes in alveolar rhab-
domyosarcoma. Hum Mol Genet. 1996;5:15–21.
99. Biegel JA, Meek RS, Parmiter AH, Conard K, Emanuel BS. Chromosomal
translocation t(1;13)(p36;q14) in a case of rhabdomyosarcoma. Genes Chromo-
som Cancer. 1991;3:483–484.
100. Douglass EC, Rowe ST, Valentine M, et al. Variant translocations of chro-
mosome 13 in alveolar rhabdomyosarcoma. Genes Chromosom Cancer. 1991;3:
101. Kay PH, Mitchell CA, Akkari A, Papadimitriou JM. Association of an un-
usual form of a Pax7-like gene with increased efficiency of skeletal muscle re-
generation. Gene. 1995;163:171–177.
102. Bennicelli JL, Advani S, Schafer BW, Barr FG. PAX3 and PAX7 exhibit
conserved cis-acting transcription repression domains and utilize a common gain
of function mechanism in alveolar rhabdomyosarcoma. Oncogene. 1999;18:
103. Barr FG, Qualman SJ, Macris MH, et al. Genetic heterogeneity in the
alveolar rhabdomyosarcoma subset without typical gene fusions. Cancer Res.
104. Nishio J, Althof P, Bailey J, et al. Use of FISH on paraffin-embedded
tissues as an adjunct to diagnosis of alveolar rhabdomyosarcoma (ARMS) [ab-
stract]. Mod Pathol. 2005;18:305A.
105. Parham DM, Qualman S, Teot L, Barr FG, Meyer WH. Correlation be-
tween histology and PAX/FKHR fusion status in alveolar rhabdomyosarcoma [ab-
stract]. Presented at: SMS 2005 International Sarcoma Meeting, June 15, 2005,
106. Crist W, Gehan EA, Ragab AH, et al. The Third Intergroup Rhabdomyo-
sarcoma Study. J Clin Oncol. 1995;13:610–630.
107. Bennicelli JL, Barr FG. Chromosomal translocations and sarcomas. Curr
Opin Oncol. 2002;14:412–419.
108. Anderson J, Gordon A, Pritchard-Jones K, Shipley J. Genes,chromosomes,
and rhabdomyosarcoma. Genes Chromosomes Cancer. 1999;26:275–285.
109. Casola S, Pedone PV, Cavazzana AO, et al. Expression and parental im-
printing of the H19 gene in human rhabdomyosarcoma. Oncogene. 1997;14:
110. Steenman M, Westerveld A, Mannens M. Genetics of Beckwith-Wiede-
mann syndrome-associated tumors: common genetic pathways. Genes Chromo-
somes Cancer. 2000;28:1–13.
111. Kurmasheva RT, Peterson CA, Parham DM, Chen B, McDonald RE, Coo-
ney CA. Upstream CpG island methylation of the PAX3 gene in human rhabdo-
myosarcomas. Pediatr Blood Cancer. 2005;44:328–337.
112. Chen B, Dias P, Jenkins JJ, SavellVH, Parham DM. Methylationalterations
of the MyoD1 upstream region are predictive of subclassification of human rhab-
domyosarcomas. Am J Pathol. 1998;152:1071–1079.
113. Scrable HJ, Johnson DK, Rinchik EM, Cavenee WK. Rhabdomyosarcoma-
associated locus and MYOD1 are syntenic but separate loci on the short arm of
human chromosome 11. Proc Natl Acad Sci U S A. 1990;87:2182–2186.
114. Chen B, He L, Savell VH, Jenkins JJ, Parham DM. Inhibition of the inter-
feron-gamma/signal transducers and activators of transcription (STAT) pathway by
hypermethylation at a STAT-binding site in the p21WAF1 promoter region.Cancer
115. Seidel C, Bartel F, Rastetter M, et al. Alterations of cancer-related genes
in soft tissue sarcomas: hypermethylation of RASSF1A is frequently detected in
leiomyosarcoma and associated with poor prognosis in sarcoma. Int J Cancer.
116. Devoe K, Weidner N. Immunohistochemistry of small round-cell tumors.
Semin Diagn Pathol. 2000;17:216–224.
117. Damore ESG, NinfoV. Soft tissue small round cell tumors: morphological
parameters. Semin Diagn Pathol. 1996;13:184–203.
118. Meis-Kindblom JM, Stenman G, Kindblom LG. Differential diagnosis of
small round cell tumors. Semin Diagn Pathol. 1996;13:213–241.
119. Pinto A, Tallini G, Novak RW, Bowen T, Parham DM. Undifferentiated
rhabdomyosarcoma with lymphoid phenotype expression. Med Pediatr Oncol.
120. Etcubanas E, Peiper S, Stass S, Green A. Rhabdomyosarcoma, presenting
as disseminated malignancy from an unknown primary site: a retrospective study
of ten pediatric cases. Med Pediatr Oncol. 1989;17:39–44.
121. Coffin CM, Rulon J, Smith L, Bruggers C, White FV. Pathologic features
of rhabdomyosarcoma before and after treatment: a clinicopathologic and im-
munohistochemical analysis. Mod Pathol. 1997;10:1175–1187.
122. Adami F, Sancetta R, Trentin L, et al. The pediatric rhabdomyosarcoma
translocation (2;13)(q35; q14) in B-prolymphocytic leukemia. Leukemia. 1993;7:
123. GolubTR, Slonim DK,Tamayo P, et al. Molecular classification of cancer:
class discovery and class prediction by gene expression monitoring. Science.
124. Dehner LP. On trial: a malignant small cell tumor in a child: four wrongs
do not make a right. Am J Clin Pathol. 1998;109:662–668.
125. Raney RB, Asmar L, Newton WA, et al. Ewing’s sarcoma of soft tissues
in childhood: a report from the Intergroup Rhabdomyosarcoma Study, 1972 to
1991. J Clin Oncol. 1997;15:574–582.
126. Grier HE, Krailo MD, Tarbell NJ, et al. Addition of ifosfamide and eto-
poside to standard chemotherapy for Ewing’s sarcoma and primitive neuroecto-
dermal tumor of bone. N Engl J Med. 2003;348:694–701.
127. Parham DM, Dias P, Kelly DR, Rutledge JC, Houghton P. Desmin posi-
tivity in primitive neuroectodermal tumors of childhood. Am J Surg Pathol. 1992;
128. Stevenson AJ, Chatten J, Bertoni F, Miettinen M. CD99 (p30/32MIC2) neu-
roectodermal/Ewing’s sarcoma antigen as an immunohistochemical marker: re-
view of more than 600 tumors and the literature experience. App Immunohis-
129. Folpe AL, Hill CE, Parham DM, O’Shea PA, Weiss SW. Immunohisto-
chemical detection of FLI-1 protein expression: a study of 132 round cell tumors
with emphasis on CD99-positive mimics of Ewing’s sarcoma/primitive neuroec-
todermal tumor. Am J Surg Pathol. 2000;24:1657–1662.
130. Boue DR, Parham DM, Webber B, Crist WM, Qualman SJ. Clinicopath-
ologic study of ectomesenchymomas from Intergroup Rhabdomyosarcoma Study
Groups III and IV. Pediatr Dev Pathol. 2000;3:290–300.
131. Kawamoto EH, Weidner N, Agostini RM, Jaffe R. Malignant ectomesen-
chymoma of soft tissue: report of two cases and review of the literature. Cancer.
132. Sorensen PH, Shimada H, Liu XF, Lim JF, Thomas G, Triche TJ. Biphen-
otypic sarcomas with myogenic and neural differentiation express the Ewing’s
sarcoma EWS/FLI1 fusion gene. Cancer Res. 1995;55:1385–1392.
133. Pellin A, Boix J, Blesa JR, Noguera R, Carda C, Llombart-Bosch A. EWS/
FLI-1 rearrangement in small round cell sarcomas of bone and soft tissue detected
by reverse transcriptase polymerase chain reaction amplification. Eur J Cancer A.
134. Le Douarin NM, Ziller C. Plasticity in neural crest cell differentiation.
Curr Opin Cell Biol. 1993;5:1036–1043.
135. Ordonez NG, El-Naggar AK, Ro JY, Silva EG, Mackay B. Intra-abdominal
desmoplastic small cell tumor: a light microscopic, immunocytochemical, ultra-
structural, and flow cytometric study. Hum Pathol. 1993;24:850–865.
136. Ordonez NG. Desmoplastic small round cell tumor, I: a histopathologic
study of 39 cases with emphasis on unusual histological patterns. Am J Surg
137. Hill DA, O’Sullivan MJ, Zhu X, et al. Practical application of molecular
genetic testing as an aid to the surgical pathologic diagnosis of sarcomas: a pro-
spective study. Am J Surg Pathol. 2002;26:965–977.
138. Brooks JS, Freeman M, Enterline HT. Malignant ‘‘Triton’’ tumors. Natural
history and immunohistochemistry of nine new cases with literature review. Can-
139. Woodruff JM, Perino G. Non-germ-cell or teratomatous malignanttumors
Arch Pathol Lab Med—Vol 130, October 2006 Rhabdomyosarcomas—Parham & Ellison
showing additional rhabdomyoblastic differentiation, with emphasis on the ma-
lignant triton tumor. Semin Diagn Pathol. 1994;11:69–81.
140. Ellison DA, Corredor-Buchman J, Parham DM, Jackson RJ. Malignant tri-
ton tumor presenting as a rectal mass in an 11 month old. Pediatr Dev Pathol.
141. McComb EN, McComb RD, DeBoer JM, Neff JR, Bridge JA. Cytogenetic
analysis of a malignant triton tumor and a malignant peripheral nerve sheath
tumor and a review of the literature. Cancer Genet Cytogenet. 1996;91:8–12.
142. Velagaleti GV, Miettinen M, Gatalica Z. Malignant peripheral nerve
sheath tumor with rhabdomyoblastic differentiation (malignant triton tumor) with
balanced t(7;9)(q11.2;p24) and unbalanced translocationder(16)t(1;16)(q23;q13).
Cancer Genet Cytogenet. 2004;149:23–27.
143. Garvin AJ, Surrette F, Hintz DS, Rudisill MT, Sens MA, Sens DA. The in
vitro growth and characterization of the skeletal muscle component of Wilms
tumor. Am J Pathol. 1985;121:298–310.
144. Conran RM, Hitchcock CL, Waclawiw MA, Stocker JT, Ishak KG. Hepa-
toblastoma: the prognostic significance of histologic type. Pediatr Pathol. 1992;
145. Hill DA. USCAP Specialty Conference: case 1-type I pleuropulmonary
blastoma. Pediatr Dev Pathol. 2005;8:77–84.
146. HachitandaY, Aoyama C, Sato JK, Shimada H. Pleuropulmonaryblastoma
in childhood: a tumor of divergent differentiation. Am J Surg Pathol. 1993;17:
147. Carpentieri DF, Nichols K, Chou PM, Matthews M, Pawel B, Huff D. The
expression of WT1 in the differentiation of rhabdomyosarcoma from other pedi-
atric small round blue cell tumors. Mod Pathol. 2002;15:1080–1086.
148. Folpe AL, Patterson K, Gown AM. Antibodies to desmin identify the blas-
temal component of nephroblastoma. Mod Pathol. 1997;10:895–900.
149. Montgomery E, Goldblum JR, Fisher C. Myofibrosarcoma: a clinicopath-
ologic study. Am J Surg Pathol. 2001;25:219–228.
150. Hojo N, Newton WA Jr, Hamoudi AB, et al. Pseudosarcomatous myofi-
broblastic tumor of the urinary bladder in children: a study of 11 cases with
review of the literature—an intergroup rhabdomyosarcoma study. Am J Surg
151. Parham DM, Reynolds AB, Webber BL. Use of monoclonal antibody1H1,
anti-cortactin, to distinguish normal and neoplastic smooth muscle cells: com-
parison with anti-alpha-smooth muscle actin and anti-muscle specific actin.Hum
152. Smith LM, Anderson JR, Coffin CM. Cytodifferentiation and clinical out-
come after chemotherapy and radiation therapy for rhabdomyosarcoma (RMS).
Med Pediatr Oncol. 2002;38:398–404.