FOLLICULAR LYMPHOMA OF THE RECTUM

Editor,

Non-Hodgkin’s lymphoma compromises a diverse group of malignant neoplasms, rarely involving the colorectum. ^{1, 2} Follicular lymphoma is a common subtype and constitutes 1%–3% of all primary gastrointestinal tract lymphomas. ^{1, 3} There are very few cases reported of recurrence of follicular lymphoma in the rectum. ⁴ Rectal follicular lymphoma is difficult to diagnose due to limited available data, low clinical suspicion and non-specific symptoms. It also has variable growth pattern and ill-defined histopathological picture, making it difficult to distinguish from benign proliferative lymphoid lesions. ³

This 67-year-old lady presented in January 2010 with a right neck mass. Initially she was managed with watchful waiting for putative atypical lymphoproliferative disorder, but in August 2011 histopathology confirmed follicular non-Hodgkin’s lymphoma which was treated successfully with chemotherapy. In May 2016 she presented with worsening faecal incontinence and a palpable rectal mass. Clinically, this appeared to be a low rectal adenocarcinoma. [Figure 1 – Endoscopic appearance of low rectal lesion (arrowed)]. Magnetic resonance imaging (MRI) and computed tomography (CT) confirmed this rectal tumour extending to the anorectal junction with a radiological staging offered at – T3N1Mx. [Figure 2 – MRI view (coronal) demonstrating the low rectal lesion]. The initial biopsy showed a probable high-grade lymphoma, but two subsequent biopsies demonstrated only chronic inflammation. Another biopsy in December 2016 confirmed the presence of a low-grade follicular lymphoma. The patient was clinically stable and given the locality of the disease and the significant risks of chemo/radiotherapy a ’watch and wait’ approach was chosen. However, her symptoms progressed and in January 2018 she had low-dose radiotherapy in the pelvis. As of September 2018, the patient has had a relapse confirmed and is under the ongoing care of haematology/oncology.

Figure 1. Endoscopic appearance of low rectal lesion (arrowed).

Figure 2. MRI view (coronal) demonstrating the low rectal lesion.

Gastrointestinal tract follicular lymphomas have usually inert clinical course. Patients can present with various non-specific symptoms, but faecal incontinence has not been previously reported in the literature. ^{1 2 5} The histopathological evaluation of colorectal follicular lymphoma can be difficult. It is not uncommon for initial histological misinterpretation and requirement of multiple biopsies before the definite diagnosis. This case emphasises the challenge of accurate histopathological diagnosis. Suitable biopsy samples and immunophenotyping analysis are recommended for accurate interpretation of the pathological diagnosis of follicular lymphoma. ^{4, 5} The management of gastrointestinal follicular lymphoma is not well established because of its rarity, but multidisciplinary approach should be undertaken. In this patient, after a watchful period, local radiotherapy was implemented with good effect. This appears in accordance to general consensus, as intestinal follicular lymphoma is usually approached as nodal follicular lymphoma and a watch-and-wait strategy or radiation therapy can be applied in case of limited disease. ¹

In conclusion, rectal follicular lymphoma is a rare presentation, but important to consider in the differential diagnosis of rectal lesions. Endoscopists should remain alert whenever they observe ambiguous lesions in the colorectum and consultation with pathologist is advised to ensure appropriate immunostaining. Histopathologists should also maintain high clinical suspicion in differential diagnosis of follicular hyperplasia of mucosa-associated lymphoid tissue.