Year : 2008 | Volume
: 51 | Issue : 2 | Page : 274--276
Embryonal rhabdomyosarcoma of the chest wall: A case report and review of the literature
Vijaya V Mysorekar1, K Harish2, Nalini Kilara3, Murali Subramanian3, AG Giridhar4,
1 Department of Pathology, M. S. Ramaiah Medical College and Hospital, Bangalore, India
2 Department of Surgical Oncology, M. S. Ramaiah Medical College and Hospital, Bangalore, India
3 Department of Medical Oncology, M. S. Ramaiah Medical College and Hospital, Bangalore, India
4 Department of Radiology, M. S. Ramaiah Medical College and Hospital, Bangalore, India
Vijaya V Mysorekar
89, A.G.«SQ»s Office Colony, 5th Main, 6th Cross, New BEL Road, Bangalore - 560 054
Embryonal rhabdomyosarcoma is a soft-tissue sarcoma which has a predilection for the head and neck area, genitourinary tract and the extremities. We report a rare case of embryonal rhabdomyosarcoma of the chest wall in an 8-year-old girl, presenting as a destructive tumor in the rib and clinically and radiologically mimicking Ewing«SQ»s sarcoma. Histopathological examination showed a small round cell tumor. Immunohistochemically, the positivity for muscle markers desmin and myogenin in the tumor cells proved to be useful for making a definitive diagnosis of embryonal rhabdomyosarcoma. Cytogenetic analysis revealed a high level of aneuploidy in the tumor cells, with double-minutes and additional chromosomal structural aberrations. The patient is responding well to chemotherapy.
|How to cite this article:|
Mysorekar VV, Harish K, Kilara N, Subramanian M, Giridhar A G. Embryonal rhabdomyosarcoma of the chest wall: A case report and review of the literature.Indian J Pathol Microbiol 2008;51:274-276
|How to cite this URL:|
Mysorekar VV, Harish K, Kilara N, Subramanian M, Giridhar A G. Embryonal rhabdomyosarcoma of the chest wall: A case report and review of the literature. Indian J Pathol Microbiol [serial online] 2008 [cited 2019 Nov 17 ];51:274-276
Available from: http://www.ijpmonline.org/text.asp?2008/51/2/274/41694
Primary soft-tissue sarcomas of the chest wall are uncommon.  Embryonal rhabdomyosarcoma is a soft-tissue neoplasm commonly encountered in childhood and adolescence. It usually occurs in the head and neck region (particularly the orbit, nasopharynx, middle ear and oral cavity), bile ducts, retroperitoneum, urogenital tract and extremities. 
We report a rare and interesting case of embryonal rhabdomyosarcoma of the chest wall, probably arising from the sixth rib, clinically and radiologically mimicking an Ewing's sarcoma. To our knowledge, rhabdomyosarcoma arising from the rib has not been reported in the literature.
An 8-year-old girl presented with a painful, rapidly growing swelling on the right side of the chest since 20 days and intermittent low-grade fever. There was no history of cough. On examination, a hard and tender mass measuring 2 cm × 2 cm was palpable in the right chest wall. The mass had well-defined borders and was fixed to the underlying bone. Computed tomography (CT) scan of the chest revealed an extrapleural heterogeneous mass apparently arising from and partly destroying, the shaft of the right sixth rib [Figure 1]. There was no evidence of calcification in the mass. The widest part of the mass measured 5.4 cm. The mass was bilobed, extending medially up to the azygos vein and laterally displacing the chest wall muscles. There was right-sided pleural effusion. A small nodule measuring about 0.5 cm in diameter, suspicious of metastasis, was found in the left lung. A clinical and radiological diagnosis of Ewing's sarcoma arising from the right sixth rib was made. A trucut biopsy of the mass was performed. At the time of biopsy, fine-needle aspiration from the mass was done and the material was taken for cytogenetic study.
Histopathological examination of the biopsied tissue showed sheets of uniform small round tumor cells with oval, hyperchromatic nuclei and scanty cytoplasm. Perivascular arrangement of tumor cells was seen [Figure 2]. Large areas of necrosis were present. Cytogenetic study on the tumor cells revealed absence of the translocation t(11;22)(q24;q12), which is diagnostic of Ewing's sarcoma. There were other cytogenetic abnormalities in the form of multiple trisomies and tetrasomies, addition of genetic material on chromosome 1, duplication of bands p22-24 on chromosome 3 and loss of chromosome 13 [Figure 3A]. A striking cytogenetic finding was the presence of double-minutes [Figure 3B], which raised the suspicion of neuroblastoma where they are most commonly observed. On immunohistochemical study, the tumor was found to be CD99 negative, ruling out Ewing's sarcoma. There was also WT1 and cytokeratin negativity. Strong positivity for desmin and, in particular, dense positivity for skeletal muscle-specific myogenin in the nuclei of the tumor cells [Figure 4] established the diagnosis of embryonal rhabdomyosarcoma.
In accordance with the Intergroup Rhabdomyosarcoma Study (IRS)-IV protocol,  the patient was put on a polychemotherapy regimen, which consists of vincristine 1.5 mg/m 2 weekly, along with cyclophosphamide 2.2 g/m 2 on day 1 and actinomycin D 0.015 mg/kg/day for 5 days repeated every 3 weeks. A CT scan evaluation after completion of 9 weeks out of the prescribed 42 weeks of chemotherapy, revealed almost total disappearance of the soft-tissue mass. A small residual sixth-rib lesion with minimal soft tissue involvement remained. The right pleural effusion had resolved and the nodule in the left lung had completely regressed.
In a review of 149 cases of sarcomas of the chest wall in patients aged between 3 weeks and 86 years, the incidence of embryonal rhabdomyosarcoma was found to be 9%.  It has been suggested that the origin of rhabdomyosarcomas may be the transformation of skeletal muscle cell precursors in the form of satellite cell myoblasts located beneath the basement membrane of the skeletal fibre.  Rhabdomyosarcoma cells exhibit sustained proliferation with inability to reach terminal differentiation.  However, evidence of rhabdomyosarcoma in sites which lack intrinsic skeletal muscle suggests that the tumor may also originate from primitive uncommitted mesenchymal cells or multipotent stem cells. ,
Ewing's sarcoma is the first diagnosis considered when the clinical presentation is of a painful, destructive bone tumor accompanied by fever in a child. To our knowledge, there have been no reports of embryonal rhabdomyosarcoma of the ribs, in the literature, although this tumor has been reported in other bones like the temporal bone.  However, in our case, we cannot deny the possibility of the tumor originating from the intercostal muscle and invading the rib. Bone invasion by a rhabdomyosarcoma has been described to occur in more than 20% of patients. 
Although complex karyotypes with numerical and structural aberrations involving various chromosomes have been described, unlike in the alveolar variant, no consistent or specific chromosomal gains or losses have been described in the embryonal variant of rhabdomyosarcoma.  Double-minutes have been commonly described in neuroblastomas  but have also often been found in embryonal rhabdomyosarcomas, where they have been linked to chromosomal instability produced by gene amplification  or overexpression of various genes such as the Aurora Kinase (AURKA) gene. 
Patients with embryonal rhabdomyosarcoma generally respond very well to chemotherapy, as in our case. However, the chest wall being an unfavorable site for rhabdomyosarcoma,  a prolonged follow-up is necessary to evaluate the outcome of treatment.
In conclusion, embryonal rhabdomyosarcoma of the chest wall is an uncommon tumor; and as it caused extensive rib destruction, it was confused with Ewing's sarcoma in our case. Cytogenetic study and immunohistochemistry proved useful in precisely typing the tumor and planning appropriate therapeutic measures.
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