Pleomorphic rhabdomyosarcoma involving the pericardium and lung pleura
By Alison Lawhead, DO; Gina Benaquista, BS; Andrew Halpern, MD
Multidetector (16-slice) CT axial images of the chest were obtained
after the administration of intravenous contrast (GE Medical
Systems, Waukesha, WI). Imaging revealed a rind of partially
necrotic soft tissue completely replacing the normal pericardium
(Figure 1). Massive contiguous pathologic adenopathy was also noted
in the right cardiophrenic region. Tumor extended superiorly to
surround the great vessels leading to compression of the left
pulmonary artery (Figure 2). The left mainstem bronchus was also
narrowed by significant tumor mass effect. A large volume of fluid
was noted within the right lateral portion of the superior aortic
recess. The patient progressed rapidly to the point of cardiac
tamponade, presumably as a result of these combined factors.
Rhabdomyosarcoma (RMS) is a malignant skeletal muscle neoplasm that
is histologically subclassified into the embryonal, alveolar, and
pleomorphic variants. Typically a childhood malignancy, RMS is
exceedingly rare in adults. Soft tissue sarcomas comprise <1% of
all adult malignancies, and RMS accounts for 3% of all soft tissue
Pleomorphic RMS is characterized by bizarre
polygonal, round, and spindle cells displaying evidence of skeletal
muscle differentiation without identifiable alveolar or embryonal
components. Pleomorphic RMS is the most common RMS subtype reported
in adults, typically occurring in men in their sixth decade of life
and usually found within the deep skeletal muscles of the
extremities and trunk.
Currently, the diagnosis of pleomorphic RMS is best suggested by
clinical presentation, radiographic findings, and light microscopy,
but this diagnosis requires either immunohistochemical or
ultrastructural confirmation. Pleomorphic RMS is variably
immunoreactive for desmin and always reactive for vimentin and
actin isoforms.2 On ultrastructural exam, diagnosis is
confirmed with identification of the spectrum of rhabdomyoblastic
differentiation and rudimentary sarcomere formation consisting of Z
bands or Z band material.3 Radiographic analysis usually
shows large masses of variable attenuation due to necrosis and
The histologic variant and location of adult RMS influences
prognosis. Treatment must be aggressive because of the nature of
this neoplasm, generally combining surgery and chemotherapy, with
or without radiation. As shown in previous studies, the prognosis
for adults with RMS is quite poor, with a mortality rate >70%,
in comparison with the prognosis for children with RMS, with a
mortality rate of <45%.5-7 This patient died 3 months
after the initial diagnosis.
The mediastinal tumor samples taken from our patient stained
positively for vimentin, muscle-specific actin, and desmin and were
negative for cytokeratin AE 1/3, cytokeratin 7, cytokeratin 20,
epithelial membrane antigen (EMA), calretinin, S100 protein,
melanoma antibody (HMB45), and leukocyte common antigen. Tumor
samples revealed high-grade large-cell malignancy with extensive
necrosis. Sections of tumor showed areas of large "giant"
multinucleated anaplastic rhabdomyoblasts, thus making the
diagnosis of pleomorphic RMS involving the pericardium and lung
In adults, pleomorphic RMS rarely arises in the
mediastinum.4 To date, few instances of mediastinal
pleomorphic RMS have been reported, thus it is imperative that new
cases are documented as treatment options are further defined.
Therapeutic success in treating adults with pleomorphic RMS has
been limited, and long-term survival rates remain poor, in the
range of 35% to 45%.4 Clinical experience is limited to
case reports, small series, and nonrandomized therapeutic
approaches.3,7 The purpose of this report is to
highlight the aggressive nature of adult RMS with the intention of
stimulating further research into the appropriate management of
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Pleomorphic rhabdomyosarcoma involving the pericardium and lung pleura.
August 15, 2006