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September 2022, Volume 72, Issue 9

IMAGING CORNER

18F FDG PET-CT Super scan: Paediatric Rhabdomyosarcoma

Hadia Saeed  ( Department of Nuclear Medicine Shaukat Khanum Memorial Cancer Hospital and Research Center, Lahore, Pakistan. )
Aamna Hassan  ( Department of Nuclear Medicine, Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore, Pakistan )
Haleema Saeed  ( Department of Nuclear Medicine Shaukat Khanum Memorial Cancer Hospital and Research Center, Lahore, Pakistan. )
Sana Munir Gill  ( Department of Nuclear Medicine, Shaukat Khanum Memorial Cancer Hospital and Research Center Lahore, Pakistan )

Abstract

Rhabdomyosarcoma (RMS) is the most common paediatric soft-tissue sarcoma, making 50% of all diagnosed cases. It is a complex disease that has the potential to arise from any tissue of the body except the bones. There are four types of rhabdomyosarcoma; embryonal, botryoidal, alveolar and pleomorphic. [18F]-FDG PET-CT plays a vital role in staging, response evaluation and follow-up of the disease. Due to significant morbidity and mortality with high-risk disease, proper staging is of paramount importance.  Staging of rhabdomyosarcoma depends on tumour localization, infiltration of local structures by the primary tumour, nodal involvement, and presence of visceral metastases. Without timely intervention, rhabdomyosarcoma progresses at an exponential speed.

 

Keywords: Rhabdomyosarcoma, [18F]-fluorodeoxyglucose positron emission tomography- computed tomography super scan,  hydronephrosis.

 

DOI: https://doi.org/10.47391/JPMA.22-96

 

Discussion

 

A 3 1/2 year old boy presented with left leg embryonal rhabdomyosarcoma and regional nodal metastases on conventional radiological imaging. He absconded after receiving one cycle of chemotherapy. At re-presentation 2.5 months later, he had skin ulceration and bleeding from the primary tumour site. Re-staging 18F FDG PET-CT was performed which revealed extensive local disease with distant metastases. (Figure) FDG PET-CT scan showed a large exophytic mass involving the entire left leg with extensive abdominopelvic and retroperitoneal nodal masses resulting in limb oedema and left renal hydronephrosis. In addition, metastatic left supraclavicular nodes were noted. Reduced cerebral metabolic activity was suggestive of FDG Superscan of malignancy.

 

 

Paediatric rhabdomyosarcoma constitutes about 3–5% of all malignancies in childhood.1 It can arise from any muscle in the body and has a complicated course depending on patient’s age, primary tumour location and presence or absence or metastases at presentation. In younger population head and neck are most common sites, followed by genitourinary tract and only 2% cases arise from limbs.2 Most paediatric patients are <10 years of age as was our patient as well.3 Symptoms can result due to compression of local structures. A multimodal approach using surgery, chemoradiotherapy is used for management.2

PET is a valuable tool for staging, assessing prognosis and leading to improved survival with early treatment.4 Hepatic and skeletal 18F FDG super scans have been reported in literature.5 In our patient, due to markedly increased FDG uptake by primary tumour and its metastases, cerebral metabolic activity was significantly suppressed hence super scan of rhabdomyosarcoma was visualized.

 

 

References

 

1.       Miller RW, Young JL Jr, Novakovic B. Childhood cancer. Cancer. 1995;75(1 Suppl):395-405.

2.       Hayes-Jordan A, Andrassy R. Rhabdomyosarcoma in children. Curr Opin Pediatr. 2009;21:373-8

3.       Arndt CA, Crist WM. Common musculoskeletal tumors of childhood and adolescence. N Engl J Med. 1999;341:342-52.

4.       Baum SH, Frühwald M, Rahbar K, Wessling J, Schober O, Weckesser M. Contribution of PET/CT to prediction of outcome in children and young adults with rhabdomyosarcoma. J Nucl Med. 2011 ;52:1535-40.

5.       Kim DW, Kim CG, Park SA, Jung SA, Yang SH. Metabolic super scan in F-FDG PET/CT imaging. J Korean Med Sci. 2010;25:1256-7.

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