Rectal lymphoma

Clinical History

A 69-year-old male patient presented with symptoms of diarrhoea of 6 months or longer and constitutional syndrome. The colonoscopy identified an oedematous mucosa covered with fibrin; located 5 cm from anus and it was unable to progress distally.

Imaging Findings

MRI showed bulky ovoid mass, homogeneous and well-defined margins involving pelvis and lower abdomen. The tumour appeared to arise from a diffuse concentric thickening of rectum and extended inferiorly to 6 cm of the anal margin. The mass also abutted and compressed bladder and prostate without infiltration, therefore extended superiorly encasing inferior mesenteric vessels.
No enlarged inguinal or pelvic lymph nodes were identified in the pelvic MRI. Retroperitoneal lymph nodes were observed on the CT examination. The biopsy was positive for lymphoma.

Discussion

Primary rectal lymphoma is an uncommon disorder accounting for 0.1% of all primary rectal tumours. There is a slight male predilection, typically occurring between the ages of 50 and 70 years [1]. Although all histological subtypes of nodal lymphomas may arise in the gastrointestinal tract, the major two appearing in more than 90% of the cases are diffuse large B-cell and mucosa-associated lymphoid tissue (MALT).
Risk factors reported to be associated with the development of primary colorectal lymphoma include inflammatory bowel disease and immunosuppression (post-transplant or AIDS).
Patients with rectal lymphoma usually present with signs and symptoms suggestive of primary rectal carcinoma, as weight loss, rectal bleeding or alteration in bowel habits, obstruction being a rare event [2].
The lack of specific symptoms often leads to delays in diagnosis and advanced stage at presentation, detecting a bulky disease in more than 50% of patients.
Typical radiographic findings include huge homogeneous mural mass, or marked concentric wall thickening involving the rectum, with luminal restriction and minor obstruction.
Features that help suspect lymphoma include well-defined margins with preservation of fat planes, no invasion into adjacent structures and perforation with no desmoplastic reaction.
MRI is used in local staging, usually has homogeneous intermediate signal intensity on T1-weighted MR images and homogeneous medium signal intensity on T2-weighted images. Mild to moderate enhancement is seen after the intravenous administration of gadolinium-based contrast material [3].
CT examinations can show extraluminal, anatomic information regarding tumour size, depth of invasion, and regional lymph node involvement. PET may also aid in the follow-up of patients with lymphomas [4].
Treatment varies from chemo-therapy alone to multimodal therapies combining surgery, chemotherapy and radiotherapy [5]. The case we reported was treated with chemotherapy.
In conclusion, rectal lymphoma must be suspected when a bulky homogeneous mass is found encasing and displacing structures causing uncommonly intestinal obstruction.

Differential Diagnosis List

Final Diagnosis

B-cell lymphoma of the rectum.

URL:	https://www.eurorad.org/case/11253
DOI:	10.1594/EURORAD/CASE.11253
ISSN:	1563-4086