Rhabdomyosarcoma, a malignant tumor with striated muscle differentiation, is rarely located in the biliary tract as the primary site. Because of its rarity, this tumor may cause diagnostic and treatment difficulties, and, so far, no therapeutic guidelines specific for this tumor location are available. Here, we describe a 2-year-old female patient who presented with a 20-cm progressive abdominal mass causing respiratory distress and feeding difficulties. Magnetic resonance imaging showed a hepatic mass extending into the peritoneal cavity, with cystic and solid components. The patient first received 12 weeks of chemotherapy (vincristine, cisplatin, doxorubicin, cyclophosphamide, actinomycin-D), which reduced the abdominal circumference and the tumor size. The patient then underwent orthotopic liver transplant from her father following total hepatectomy. She was discharged 2 weeks posttransplant without complications, and 4 additional chemotherapy cycles were planned. Although no standard guidelines exist, tumor reduction before transplant appears to be a viable approach.

Key words : Embryonal biliary rhabdomyosarcoma, Rare disease, Tumor

Introduction
Rhabdomyosarcoma is a malignant tumor with striated muscle differentiation, with the biliary tract being an extremely rare primary site (0.5%–1.5% of pediatric cases). However, this is the most common malignancy in this location in children. Because of the tumor’s rarity and location, it may cause diagnostic and treatment difficulties. In addition, no therapeutic guidelines specific for this tumor location are available. Here, we report a case of embryonal biliary rhabdomyosarcoma treated with neoadjuvant chemotherapy and liver transplant.

Case Report
A 2-year-old Moroccan girl presented with a progressive abdominal mass causing respiratory distress and feeding difficulties. A biopsy in Morocco diagnosed alveolar rhabdomyosarcoma, and 2 cycles of chemotherapy with vincristine, actinomycin-D, and cyclophosphamide were given, but the tumor continued to enlarge. On admission, she had a 20-cm abdominal mass (Figure 1). Laboratory tests revealed mild anemia (hemoglobin level of 9 g/dL), elevated lactate dehydrogenase (1031 IU/dL), and elevated uric acid (7 mg/dL), although liver function tests and tumor markers were normal. Magnetic resonance imaging showed a 240 × 224 × 156-mm hepatic mass extending into the peritoneal cavity, with cystic and solid components. Positron emission tomography-computed tomography demonstrated FDG uptake (SUVmax = 2.3) without distant metastases. A Tru-cut biopsy confirmed embryonal rhabdomyosarcoma (Figure 2A). The patient received 12 weeks of chemotherapy (vincristine, cisplatin, doxorubicin, cyclophosphamide, actinomycin D), which reduced abdominal circumference from 78 cm to 60 cm. Follow-up magnetic resonance imaging showed tumor shrinkage (199 × 195 × 114 mm) with necrosis and hemorrhage, but no lymphadenopathy or peritoneal involvement. The patient then underwent orthotopic liver transplant from her father following total hepatectomy. Histopathology of the 37.5 × 19 × 11-cm, 2755-g liver revealed a 20 × 20 × 11-cm tumor. Immunohistochemistry showed desmin, myogenin, and MyoD¹ positivity, focal SMA positivity, and S100 negativity, with a Ki-67 index of 2% (Figure 2, B and C). She was discharged 2 weeks posttransplant without complications, and 4 additional chemotherapy cycles were planned.

Discussion
Rhabdomyosarcoma of the biliary tract is a rare tumor in children, with incidence ranging from 0.5% to 0.8% of childhood rhabdomyosarcoma.¹ No clear guidelines on treatment are available. In our patient, the tumor was highly chemosensitive; therefore, initial chemotherapy resulted in tumor shrinkage and gave a chance for liver transplant to be performed. In selected cases, radiotherapy can be used for local disease control. Swieszkowska and colleagues reported 8 children with biliary rhabdomyosarcoma, 7 of whom received 4 to 9 courses of neoadjuvant chemotherapy.² One patient received a Whipple procedure, with total hepatectomy and liver transplant from a living donor. Follow-up showed that 75% of patients were alive (follow-up range of 1.2-27 years).² In a study from Urla and colleagues, 17 patients with biliary rhabdomyosarcoma were evaluated; 5-year overall survival and event-free survival for the whole group were 58% (range, 45%-71%) and 47% (range, 34%-50%), respectively.³ In a meta-analysis from Fuchs and colleagues, 176 patients with biliary rhabdomyosarcoma were analyzed, and overall survival and progression-free survival were 51% and 50%, respectively.⁴ Absence of surgical resection was found to be an independent risk factor for death.¹ In our patient, the tumor was totally resected with liver transplant. However, further chemotherapy for control of microscopic disease after surgery was warranted in our patient.

Conclusions
Primary hepatic or biliary rhabdomyosarcoma is rare. Neoadjuvant chemotherapy can reduce tumor burden, enabling complete surgical resection or transplant. Embryonal rhabdomyosarcoma has the best prognosis, whereas alveolar and pleomorphic subtypes are more aggressive. Although no standard guidelines exist, tumor reduction before transplant appears to be a viable approach.