Gluteal region rhabdomyosarcoma with contiguous intra-abdominal spread (ONLINE ONLY)

Findings

Radiography of the abdomen revealed a large, lobulated, soft tissue mass in the left gluteal region and a soft tissue haze in the left side of the abdomen. The bowel loops were displaced to right side. There was no evidence of bone destruction or any calcification (Figure 1).

Ultrasound examination revealed a heterogeneous, solid mass with few cystic areas in the left gluteal region. A mass with similar imaging appearance was also seen in the left side of the abdomen that extended from the midpole of the left kidney to the pelvis, displacing the bowel loops and urinary bladder to the right side (Figure 2). There was no ascites, and the other intra-abdominal organs were normal.

CT of the abdomen and pelvis showed a lobulated, hypodense, noncalcified mass in the left gluteal region (Figure 3). Following contrast administration, heterogenous enhancement was seen. The mass also showed invasion of the omentum and the mesentery and loss of planes with the aorta, inferior vena cava, adjacent bowel, left kidney, ureter, and urinary bladder.

On MRI, the mass appeared hypointense to muscle on T1-weighted images and hyperintense on T2-weighted images. Following the administration of gadolinium contrast, T1-weighted fat-saturated scans showed intense enhancement with interspersed nonenhancing areas (Figure 4).

SURGICAL AND PATHOLOGIC FINDINGS

Following excision of the gluteal region mass, laparotomy was performed. Complete resection of the intra-abdominal mass was not possible, and debulking surgery was attempted. Subsequently, multiple chemotherapy was initiated. A gelatinous septate mass was removed; the dorsal mesentery, anterior retroperitoneal fascia, left lateroconal fascia, sigmoid colon mesentry, and the left ureter were adherent to the mass. Histopathologic analysis revealed embryonal-type rhabdomyosarcoma--a less frequently noted tumor subtype in extremities.

Discussion

Rhabdomyosarcoma represents approximately 5% to 15% of all solid malignant tumors in children.¹ Two major types have been described: adult-pleomorphic and juvenile, which consists of elements of alveolar, embryonal, and botryoid with 1 element usually predominating. A mixed group has also been suggested to describe a mixture of these cell types.² The head and neck region is most often involved (40%), while other commonly reported sites are the genitourinary organs, the retroperitoneum, and the extremities.³

Although alveolar histology has more often been reported in extremity tumors,⁴ in this case, histopathologic examination revealed embryonal rhabdomyosarcoma in the present case.

Metastatic spread of rhabdomyosarcoma is known to be diverse and is more often seen in primary tumors of the extremities and in those with alveolar histology. It usually occurs via the hematogenous or lymphatic route. Diffuse intraperitoneal involvement is rare in both primary and metastatic forms.¹ However, secondary extension into the abdomen from retroperitoneal or pelvic rhabdomyosarcoma is relatively frequent.⁵ Commonly reported findings in intraperitoneal rhabdomyosarcoma include ascites, intraperitoneal nodules or masses, omental caking, or a pseudomyxoma peritonei appearance.¹ However, no ascites was noted in the present case.

MRI of rhabdomyosarcoma shows a heterogenous mass, which indicates the presence of blood or necrosis. The mass appears isointense to muscle on T1-weighted imaging and shows intensity equal to or greater than fat on T2-weighted imaging.⁴ The MRI features in the present case are consistent with previously reported findings, as the mass appeared slightly hypointense to muscles on T1-weighted imaging and hyperintense to fat on T2-weighted imaging.

The first choice of treatment for rhabdomyosarcoma is complete surgical excision; although chemotherapy also plays an important role because of its high chemosensitivity. Intensive multiagent chemotherapy, as was used in our patient, has been suggested for patients with gross residual or metastatic disease.⁶

CONCLUSION

Our case documents an uncommon presentation of extremity rhabdomyosarcoma with contiguous intra-abdominal spread involving the subcutaneous tissue, adjacent anterolateral abdominal wall, omentum, dorsal mesentry, and anterior retroperitoneal fascia.

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3. Kaplan AM, Creager AJ, Livasy CA, et al. Intra-abdominal embryonal rhabdomyosarcoma in an adult. Gynecol Oncol. 1999;74:282-285.
4. Siegel MJ. Magnetic resonance imaging of musculoskeletal soft tissue masses.Radiol Clin North Am. 2001;39:701-720.
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6. Kunieda K, Saji S, Kuwabara I, et al. Rapid growth of a retroperitoneal rhabdomyosarcoma following right hemicolectomy for ascending colon cancer: Report of a case. Surg Today. 2000;30:372-375.