Peritoneal lymphomatosis: a rare presentation of follicular lymphoma mimicking peritoneal carcinomatosis

Abstract

Patients presenting with ascites associated with peritoneal disease have a wide differential diagnosis including both malignant and non-malignant related causes. We present the unusual case of a patient, clinically deteriorating, whose malignant peritoneal disease was due to an underlying follicular lymphoma. An urgent staging CT scan followed by a peritoneal biopsy allowed the patient to start chemotherapy within days of acute presentation to the hospital. This case emphasises the importance of obtaining tissue diagnosis urgently in these patients to ensure that the correct treatment can be started in a timely manner.

Background

The majority of patients presenting with malignant ascites associated with peritoneal disease have peritoneal carcinomatosis. Lymphomatous infiltration of the peritoneum is far less common. Cancers that commonly present in this manner are carcinomas originating in the gastrointestinal tract, gynaecological tumours and breast cancer. For this reason, patients will often undergo investigations focused on finding the primary, even in the absence of any localising symptoms (eg, per rectum bleeding), such as upper and lower gastrointestinal endoscopies, MRI pelvis and breast mammography which will ultimately lead to a delay in the final diagnosis. Importantly, the treatment algorithms and prognosis for these diagnoses can often be very different. Urgent biopsy and tissue diagnosis is therefore crucial in order to instigate early, effective treatment for lymphoma and to avoid unnecessary investigations for a primary carcinoma.

Case presentation

A 72-year-old man presented to A&E with a 6-week history of increasing abdominal distension associated with anorexia, generalised weakness and shortness of breath. He described a weight loss of 6 kg over a period of 3 months and reduced exercise tolerance. He denied any change in bowel habit, fevers or night sweats.

The medical history included hypertension, hypercholesterolaemia and gastro-oesophageal reflux disease. He was a non-smoker and abstained from alcohol consumption. His father had died of hepatocellular carcinoma aged 54 and his brother had previously had leukaemia.

On examination, he was cachectic with a distended abdomen and shifting dullness but no organomegaly. Cardiovascular and respiratory examinations were normal. He was afebrile; blood pressure was within normal limits and he had a sinus tachycardia of 121 bpm.

Investigations

Blood results on admission: haemoglobin 144 g/L, white cell count 5.69×10⁹/L, platelets 390×10⁹/L, sodium 136 mmol/L, potassium 5.3 mmol/L, urea 7.5 mmol/L, creatinine 88 µmol/L, albumin 30 g/L and C reactive protein 13 mg/L.

In terms of radiological investigations, because of the clinical suspicion of disseminated malignancy, he proceeded to a CT chest, abdomen and pelvis. This demonstrated extensive disseminated peritoneal disease with marked thickening of the diaphragm and the peritoneal surfaces and a large omental cake with large volume ascites. This was associated with extensive enlarged supraclavicular, mediastinal and para-aortic lymph nodes. Importantly, this radiological finding of a diffuse distribution of enlarged lymph nodes was more suggestive of peritoneal lymphomatosis rather than carcinomatosis where lymphadenopathy is localised more around the primary tumour. Mention was made that no obvious primary could be found within the gastrointestinal tract (figure 1).

Figure 1.

Axial (A), sagittal (B) and coronal (C) images from a CT scan demonstrating extensive ascites (black arrows in A) with enlarged para-aortic nodes (white arrow in A), an omental cake (white arrow in B) and marked thickening of the small bowel mesentery (white arrows in C) and thickening of the peritoneum noted (black arrow in C).

In view of the fact that he had previously been fit and well and was now acutely deteriorating, he was admitted to hospital and proceeded to an urgent biopsy of the enlarged supraclavicular lymph node (within 24 h of referral). This was reported as consistent with follicular lymphoma.

At this stage, he was referred to the haematology team who completed his staging with a bone marrow trephine biopsy and a positron emission tomography-CT scan that reported nodal disease above and below the diaphragm and extranodal involvement of the spleen, peritoneum, pericardium and pleura.

Differential diagnosis

The differential diagnosis for disseminated peritoneal disease is vast. Primary tumours that commonly present with this pattern of disease include those from the gastrointestinal tract (colorectal, gastric, pancreas and biliary tract tumours), gynaecological tumours (ovary and primary peritoneal tumours) as well as breast and lung cancer. Peritoneal mesothelioma and peritoneal sarcoma can also appear radiologically very similar to peritoneal carcinomatosis.

Smooth thickening and enhancement of the peritoneum, with stranding of the omentum and mesentery, may also be seen in intra-abdominal sepsis including peritoneal tuberculosis.

Lymphoma is a much rarer cause but needs to be considered since it is imminently treatable with chemoimmunotherapy.

Treatment

Following tissue confirmation of follicular lymphoma, the patient started an immediate course of combination chemotherapy consisting of rituximab, cyclophosphamide, vincristine and prednisolone. To date he has completed eight cycles of chemotherapy with a marked symptomatic improvement and a CT scan has confirmed a substantial reduction in tumour burden (figure 2). He remains under the care of the haematology team.

Figure 2.

Axial (A), sagittal (B) and coronal (C) images from a CT scan post-treatment, demonstrating resolution of ascites, a reduction in size of the para-aortic nodes (white arrow in A), and mild residual thickening of the small bowel mesentery (white arrows in B and C).

Outcome and follow-up

Although follicular lymphoma is incurable with chemoimmunotherapy, the prognosis is much better generally than for solid tumours, for example, gastrointestinal cancers presenting with peritoneal disease. For follicular lymphoma, one would expect to see progression-free survivals of 3–7 years, but also importantly, high-grade lymphomas presenting this way would be treated potentially with curative intent.

Discussion

The presentation of lymphoma as peritoneal lymphomatosis is relatively rare, but it needs to be thought of since the treatments and prognosis are very different from the more common causes of peritoneal carcinomatosis.^{1 2} Furthermore, while the patient we have presented was diagnosed with a low-grade follicular lymphoma, peritoneal lymphomatosis is more commonly associated with the high-grade lymphomas.^{3 4} Of note, histological evaluation of the peritoneum, in this case, was not carried out to determine whether transformation into a high-grade lymphoma had occurred.

There have been two case reports published highlighting the negative consequences that can occur as a result of not bearing this diagnosis in mind. Horger et al⁵ described the case of a 32-year-old woman presenting with abdominal pain and ascites. A CT scan demonstrated large volume ascites, extensive peritoneal involvement and an enlarged right adnexal mass, and biochemically, she had a raised serum Ca125 tumour marker level of 276 U/mL (normal <35). A presumed diagnosis of ovarian cancer was made and this patient therefore proceeded to an exploratory laparotomy, right oophorectomy and omentectomy. The histology however was subsequently reported as a high-grade lymphoblastic Burkitt-like B cell lymphoma. This patient had therefore undergone an unnecessary debulking surgical procedure and would have also had a delay starting the correct chemotherapy.

Kim et al⁶ described the case of an elderly patient with a previous history of colon cancer treated 4 years earlier presenting with abdominal pain and distension. A CT was reported as demonstrating ascites associated with thickening of the peritoneum and bowel loops. The ascites was tapped and found to be an exudate, and thus a presumptive diagnosis of recurrent bowel cancer was made and the patient was transferred to a hospice for palliative care. After a week, the cytology was reported in keeping with a diffuse large B cell lymphoma. The patient was therefore brought back to the hospital to start chemotherapy but unfortunately he deteriorated after his first cycle of treatment. The authors felt that by not expediting the histology on the assumption that any treatment would be palliative, there had been a delay in the initiation of potentially curative treatment for this patient.

In summary, while it is rare, the presentation of lymphoma as peritoneal disease does occur. Radiology alone is often not sufficient to make a diagnosis of lymphomatosis over carcinomatosis and it is therefore important to keep both in mind until a cytological or histological diagnosis has been confirmed. This is essential to prevent delay in starting lymphoma treatment, while also preventing unnecessary investigations into the primary site causing the peritoneal carcinomatosis.

Learning points.

• Presentation of lymphoma as peritoneal lymphomatosis is rare.

• It is very difficult to differentiate from peritoneal carcinomatosis on imaging alone.

• Importance of not making a presumptive diagnosis of peritoneal carcinomatosis that may delay in initiating potentially curative treatment.

• Importance of not making a presumptive diagnosis of peritoneal carcinomatosis that might lead to unnecessary investigations to find the primary delaying tissue diagnosis.