Editor,We describe a case of Non-Hodgkin's high grade B cell lymphoma of the rectum, which presented with a short history mimicking a perianal abscess. Careful examination under anaesthetic (EUA) and biopsies helped to clinch the diagnosis.
Case Report
A 76-year-old patient was admitted as an emergency with marked perianal pain for 1 week along with episodes of faecal incontinence during this period. The patient was being treated by the General Practitioner with antibiotics for suspected perianal infection.On examination there was no induration around the anus but there was a point at which patient was maximally tender. The patient was examined by three senior clinicians, they all found different points of maximum tenderness. There was no obvious abscess. Investigations on admission including full blood picture, differential count, and inflammatory markers, were all within normal limits.The patient underwent EUA rectum; no abscess, fissure or fistula was found. Rigid sigmoidoscopy revealed diffuse non-specific redness of the rectal mucosa just beyond the dentate line. Random biopsies were taken. Post operatively the patient continued to experience severe pain and remained incontinent.Pathology showed multiple fragments of rectal mucosa heavily infiltrated by a diffuse and sheeted proliferation of lymphoid cells with intermediate sized nuclei and little cytoplasm. The appearances were those of Non-Hodgkin's lymphoma-intermediate to high grade B-cell type. CT scan revealed significant soft tissue thickening of the anus extending into the proximal rectum. Maximum size measured 7cm. There was a suspicious lesion in the liver, which was confirmed to be lymphomatous on targeted ultrasound scan. There was no evidence of lymphadenopathy.Due to liver involvement and infiltration around the anus the patient was started on chemotherapy (CHOP). The pain and incontinence all but disappeared after the first dose of chemotherapy and the tumour shrank significantly. Only slight thickening remained in the bowel wall at end of 2 years on repeat CT scan. The liver lesion remained unchanged. The patient remains well and asymptomatic after four years.
Discussion
Most cases of perianal pain are due to fissure in ano, perianal abscess, fistula in ano and low rectal or infiltrating carcinoma of the anal canal.Lymphoma of the rectum is a rare condition and accounts for less than 1% of rectal malignancies. Involvement of the anal canal and the sphincters is even rarer.1,2 Lymphoma of the rectum accounts for only 4% of GI lymphomas.3 Primary colorectal lymphoma may present in a myriad of ways including perianal pain 9%, incontinence 2% or simply as an incidental finding 9%.4This patient's perianal pain did not seem unusual at the beginning. The history of incontinence did raise the possibility of an infiltrating malignancy but the short one week history and the absence of any induration on examination led us to believe otherwise. The patient had no other constitutional symptoms to direct us towards the diagnosis of a malignancy or even abscess. The difference in the examination findings between different examiners and absence of an obvious cause such as fissure or abscess raised suspicions towards an unusual cause.
Conclusion
Careful EUA and random rectal biopsy may be indicated in all patients with acute perianal pain with no evidence of usual causes such as abscess, fissure and fistula.