Introduction:

Lymphangioma is a rare, benign tumour of the lymphatic system. It is believed to be a congenital malformation, when part of the lymphatic channels fails to connect to the main lymphatic system. Lymphangioma is a tumour of the paediatric age, with 50% of patients presenting at birth. The head and neck are the main affected sites (75%), while the retroperitoneal cavity is the least affected area, and comprises less than 1% of cases. Adult lymphangioma is an extremely rare tumour, and adult retroperitoneal lymphangioma (ARL) is even a rarer tumour. 

Diagnosis of ARL is very challenging to the treating physician, as clinical presentation varies widely. Since ARLs became a known clinical entity, it has been claimed that this specific type of tumour is usually asymptomatic and discovered incidentally by non-related abdominal imaging studies, during operations or at autopsy. Moreover, abdominal magnetic resonance imaging (MRI) has been known as the diagnostic modality of choice for ARL.

Here we present a case of an incidentally detected adult retroperitoneal lymphangioma in a patient presenting with symptoms of urinary tract infection.

Clinical Profile:

A 45-year-old man came with complaints of dull aching pain in periumbilical region radiating to the right flank region with burning sensation during urination, The symptoms had been present for a day. The pain was associated with few episodes of vomiting and low-grade intermittent fever which was relieved on medication.

His laboratory investigations showed elevated WBC counts with predominant neutrophilia. A provisional diagnosis of acute pyelonephritis was made and the patient was started on IV antibiotics.  

Radiological findings:

A curvilinear ultrasound probe placed transversely in the hypogastric region showed a heterogeneously iso to hypoechoic lesion in the retroperitoneum encasing the aorta and IVC which were displaced anteriorly. Multiple enlarged lymph nodes were seen  Fig 1).  On Doppler examination the lesion did not show any significant vascularity.

On CECT  (Fig 2) , there is an ill-defined, hypodense non enhancing, cystic lesion in the retroperitoneum - predominantly involving the vascular plane, encasing the aorta and IVC. The aorta and the IVC were displaced anteriorly from the vertebral body. The lesion extends superiorly through the aortic hiatus into middle mediastinum and inferiorly till the iliac vessels- resulting in characteristic trans-compartmental extension.

On MRI (FIg 3) , it is hyperintense on T2 and hypointense on T1 sequences. On DWI, it shows no diffusion restriction. It shows signal drop on out of phase imaging. It shows no significant contrast enhancement on post contrast images.

 Figure 1 : Ultrasound probe placed transversely in the hypogastric region showed iso to hypoechoic lesion in the retroperitoneum encasing the aorta and IVC causing its upliftment from the vertebral body. Multiple enlarged lymph nodes were also seen.

Fig 2  On CECT, there is an ill-defined hypodense non enhancing cystic lesion in the retroperitoneum predominantly involving the vascular plane, encasing the aorta and IVC. It is causing upliftment of aorta from the vertebral body.

The lesion is extending superiorly till the aortic hiatus into middle mediastinum and inferiorly till the iliac vessels- resulting in characteristic trans-compartmental extension.

On MRI, the lesion shows a large, ill-defined fat intensity lesion with multiple enhancing septation involving the left perirenal, anterior and posterior pararenal and left paracolic region. Medially,  the lesion extends to the preaortic and left paraaortic region. Anteriorly it causes  anterior displacement of descending colon and small bowel loops. Posteromedially there is involvement of the left psoas and quadratus lumborum muscles. Posterolaterally it is limited by the posterior pararenal and lateral conal fascia that is thickened. Inferiorly, the lesion surrounds the inferior pole of the left kidney with mild anterior displacement. Anteriorly,  the above lesion shows a large heterogeneously enhancing soft tissue component. Another smaller enhancing soft tissue component is seen inferior to the lower pole of the left kidney.

Fig 3 On MRI, it is hyperintense on T2 and hypointense on T1 sequences. On DWI, it shows no diffusion restriction. It shows no significant contrast enhancement on post contrast images.

Radiological diagnosis:  

The differential diagnosis considered were:

1. IgG4 related Retroperitoneal fibrosis 

2. Lymphoma 

3. Retroperitoneal lymphatic malformation

Pathological diagnosis:

A  biopsy from the mass showed dilated lymphatic spaces lined with attenuated endothelial cells resembling the cells that line normal lymphatics. The lymphatic spaces were filled with proteinaceous eosinophilic fluid. The supporting stroma was composed of collagen and contained lymphoid and plasma cell aggregates. These features were consistent with a lymphatic malformation.

Final diagnosis: 

Adult retroperitoneal lymphatic malformation

Treatment:

 The patient will undergo surgery to excise the mass.

 Timeline:     

Discussion

Lymphangioma, first described in 1913 by Koch, is a rare, benign - usually cystic -  tumour of the lymphatic system [1]. It's precise pathogenesis is yet to be known and various theories regarding the development of lymphangiomas have been postulated. It is thought that these tumours arise from congenital malformations, which develop due to failure of primary lymphatic cysts to communicate with the main lymphatic channels [2]. Several factors, such as trauma, iatrogenic intra-operative injury, neoplasms, fibrosis, inflammation, lymph nodes degeneration and disorders of endothelial lymphatic vascular secretions have been raised as causative or trigger factors for development of lymphangiomas, especially during adulthood [3].

Cystic lymphangiomas could be unilocular or multilocular, and their fluid consistency might be serous or chylous, depending on the number of communicating channels and degree of lymphatic stasis, respectively [4,5].

An lymphangioma in adults is an extremely rare entity, and adult retroperitoneal lymphangioma (ARL) is an even rarer disease. [6,7]

It has been claimed that this specific type of tumour is usually asymptomatic and discovered incidentally by non-related abdominal imaging studies, during operations or at autopsy. [8,9] Abdominal magnetic resonance imaging (MRI) has been shown to be the diagnostic modality of choice for ARL. [10]

On ultrasound examinations, these malformations appear as hypoechoic to anechoic multicystic masses.

On CT,  they appear as well-defined multilocular cystic masses with typically homogeneous fluid content. Calcifications are uncommon. Post-contrast enhancement of the cyst wall and septa may be seen. They can cross fascial planes and involve multiple compartments as was in on our case. 

On MR; lesions follow fluid intensity pattern, appearing hyperintense on T2 and hypointense on T1. It shows no diffusion restriction on DWI.

Conclusion:

Primary ARL is a rare and well-known, benign lymphatic tumour with increasing incidence recently.  CT scan is the gold standard imaging modality for diagnosis with multilocular septated cystic mass being the most common finding. Complete surgical resection is the therapeutic option of choice. Tumour recurrence is rare, even in cases of incomplete tumour resection.

References

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