Teaching Case

A 54-year-old man, who had simultaneous kidney-pancreas transplantation in 2013 for diabetes was admitted because of acute epigastric and peri-umbilical pain, vomiting and asthenia. Clinical examination showed right flank and peri-umbilical sensibility. No palpable mass was noted, neither lymphadenopathy. The patient did not complain about transit disorders.

Abdominal computed tomography (CT) was performed, showing an 8-cm mesenteric mass in the ileo-caeco-appendicular region (figure 1) adjacent to a regular, circumferential, homogenous thickening of an ileal loop (figure 2). It also displayed a large infiltration of the great omentum with irregular, ill-defined, coalescing nodules (figure 3), hypodense areas on the kidney transplant (figure 4), hypodense nodules on the liver and ascites (figure 5). No lymphadenopathy nor splenomegaly was found.

Peritoneal lymphomatosis is a rare extra-nodal localization of lymphoma, predominant in aggressive lymphoma, especially diffuse large B-cell subtype [1]. The presence of lymphoid cells in a fibro-fatty tissue could be explained by a previous digestive localization leading to a contiguity spread via transverse mesocolon, gastrocolic ligament and visceral peritoneal surfaces [2]. Hematogenous and lymphatic dissemination are also suspected [3]. Peritoneal involvement can occur in patients with preexisting lymphoma or may be discovered at the time of diagnosis, with similar proportions [4].

Its diagnosis can be challenging because of a radiological presentation similar to that of other peritoneal diseases, malignant or not, in particular peritoneal carcinomatosis. The importance of an early diagnosis is reinforced by the fact that peritoneal lymphomatosis is seen in aggressive forms of lymphoma that require rapid care. This is why a prompt diagnosis of peritoneal lymphomatosis is crucial in order to avoid useless complementary exams.

There are several differential diagnoses, sometimes difficult to distinguish.

Some authors even suggested that peritoneal lymphomatosis is radiologically indistinguishable from peritoneal carcinomatosis [5].

Cabral et al. suggested several criteria helping to differentiate lymphomatosis from its two main differential diagnoses (peritoneal carcinomatosis and peritoneal sarcomatosis) and summarize this with three distinctive criteria: peritoneal lesions, lymphadenopathy and ascites. Thereby, peritoneal lymphomatosis appears to be recognized by bulky homogenous masses as peritoneal lesions, diffusely enlarged lymphadenopathy and mild to moderate ascites [1]. Conversely, multiple small nodules and lymphadenopathy located around the primary mass and large-volume ascites are more suggestive of carcinomatosis whereas bulky heterogeneous masses without lymphadenopathy and variable ascites should raise suspicion for sarcomatosis [1].

O’Neill et al. designed what we believe to be the only known statistical study on peritoneal lymphomatosis, based on 122 cases of peritoneal carcinomatosis, sarcomatosis and lymphomatosis. They showed that peritoneal carcinomatosis could be distinguished from the two others diagnoses by omental caking, peritoneal thickening and more ascites; peritoneal sarcomatosis could be identified by regular and well-defined nodules and lymphomatosis could be discerned by the presence of lymphadenopathy, splenomegaly and omental involvement [4].

This case report illustrates a rare extra-nodal involvement of aggressive lymphoma whose rapid diagnosis is crucial for the prognosis but can be really difficult to differentiate from other peritoneal diseases. Several radiological signs have been proposed by authors, the most relevant seeming to be the presence of a gastrointestinal localization of lymphoma.