Biliary rhabdomyosarcoma

2 year-old previously healthy female presenting to a pediatric hospital ER with abdominal pain, nausea, vomiting and fever.  1-month history of yellow discolouration of her eyes, pale stools and dark urine.  She was jaundiced with abdominal distention and hepatomegaly. No skin rash. Laboratory testing showed elevated liver enzymes, conjugated bilirubin, inflammatory markers and leucocytosis. 

Ultrasound demostrates intra and extrahepatic biliary dilatation (Figure 1a). There is a heterogeneous mass inside the common bile duct.

Coronal (Figure 2a) and axial (Figure 2b) T2-weighted image show a heterogenous predominantly high signal intensity mass with cysts causing biliary tree dilatation and gallbladder distension. Coronal MRCP MIP (Figure 2c) shows the biliary tree dilation and mass. B1000 (Figure 2.d) and ADC (Figure 2e) show restricted diffusion of solid components. The mass size is 23 mm x 20 mm in the axial plane.

Axial T1-weighted images with fat saturation without (Figure 3a) and after gadolinium on arterial (Figure 3b), late arterial (Figure 3c), portal (Figure 3d), and delayed phase (Figure 3e) show progressive enhancement of the solid component of the mass. Cystic components do not enhance.

Right percutaneous transhepatic cholangiography shows biliary tree dilatation. A tumour in the distal bile duct is visible. An 8F internal/external tube is inserted using a guide wire with correct placement in cholangiography (Figure 4.1; 4.2), and biopsies are taken.

Rhabdomyosarcoma is the fourth most frequent solid tumour [1] and the most common soft tissue sarcoma in pediatrics [2]. Biliary tract rhabdomyosarcoma accounts only for 0.5 to 1.5% of all RMS in children, but it is the most common malignant tumor of the biliary tract [3], being the common bile duct the most frequent primary tumour site.  These tumours progress rapidly and present early in childhood, with an average age ranging between 3.5 and 5 years in the different case series [1,2,3,4].

Pathologic subtypes of rhabdomyosarcoma include embryonal rhabdomyosarcoma, which accounts for the majority of the cases, alveolar rhabdomyosarcoma, spindle cell/ sclerosing rhabdomyosaracoma and pleomorphic rhabdomyosarcoma [1,2,6]. In more recent studies rhabdomyosarcomas are classified as FOXO1 fusion positive [carrying better pronosis] or negative, with 70/80% of alveolar rhabdomyosarcomas being FOXO1 positives [5,6].

They are typically large at diagnosis and demonstrate polypoid appearance within the biliary system. The common bile duct is the most frequent primary tumor site [3]. These tumours are isointense or slightly hyperintense to skeletal muscle on T1. T2 signal intensity varies depending on the cellular compactness. A bubbly appearance is typical of botryoid rhabdomyosarcoma which resembles a bunch of grapes [4] with a hypointense solid area interspersed with bright cystic areas, conforming the so-called botryoid sign [3]. Enhancement is heterogeneous with multiple ring enhancement resembling a bunch of grapes. Haemorrhage and necrosis may be apparent [2] and central tumour necrosis may mimic a choledochal cyst [4].

The prognosis of this type of tumour has been improving as a consequence multimodal treatment based on a combination of chemotherapy drugs, surgery and radiation. Children ≤ 10 years and botryoid tumour histology are factors related to better prognosis.

An extension  CT and PET CT were made at the initial assesment and showed no metastases. Our patient was treated with a combination of chemotherapy followed by choledochojejunostomy with microscopic negative resections margins. She did recover and is being checked yearly.

The differential diagnose should be made with choledochal sludge or choledocholithiasis. Another consideration would be a choledochal cyst in cases of tumours with central necrosis, a typical mimicker as reported in multiple case reports available in the literature. In our case, the first sonogram clearly showed a mixed solid and cystic mass inside the common bile duct.

Take Home Message

Biliary rhabdomyosarcoma is the most common mass within the biliary tract in children. Therefore, children with obstructive jaundice and a mass in the biliary tree should raise suspicion of this entity, as well as other more common causes such as choledochal cysts, choledocholiths, sludge, and strictures.
 

Written informed patient consent for publication has been obtained.