Physical examination revealed a tender left upper quadrant mass, palpable 5 cm below the costal margin. There was no peripheral lymphadenopathy, nor any evidence of respiratory or cardiovascular disease.

Gastroscopy revealed an ulcer measuring 2 × 2 cm at the gastric fundus with irregular edges, in addition to gastric varices with the presence of blood within the stomach. In view of these findings, the patient was subsequently admitted for further investigation.

CT of the chest, abdomen and pelvis demonstrated a 18.9 cm (superior–inferior) × 10 cm (anterior–posterior) × 8.6 cm (transverse) mass centred on the spleen which directly invaded neighbouring structures including the anterior peritoneal wall, pancreatic tail, left adrenal gland, greater curve of stomach and the left gastric vessels. The superior aspect of the lesion also extended up to, but did not breach, the left hemidiaphragm. Splenic vein invasion was demonstrated causing secondary venous collaterals surrounding the mass (figure 1) indicative of the slow growing nature of the mass. The tumoural lesion was heterogeneous in appearance with both solid and cystic components including central liquefied necrosis and locules of air. A direct communication, that is, a gastrosplenic fistula, between the mass and the gastric lumen was outlined with air and oral contrast (figure 2). Importantly there was no significant evidence of local or distant significant lymphadenopathy. CT imaging therefore demonstrated a large aggressive tumoural mass invading adjacent structures centred on the spleen.

In view of the extensive and unusual nature of disease, a tertiary opinion and referral was made. A further gastroscopy was performed with deep biopsies taken from the greater curve for histopathological analysis. Examination of the biopsies was consistent with diffuse large B cell lymphoma with no evidence of Helicobacter pylori-like organisms or intestinal metaplasia. The cells were CD20 positive, PACS5 positive, BCL6 positive, MUM1 positive and weakly CD10 positive. The proliferation index with MIB1 was 100%.

Extensive splenic necrosis and gastric wall infiltration is required for gastrosplenic fistula formation.⁹ It can occur after chemotherapy as a result of rapid regression of the tumour that has infiltrated the gastric mucosa thus resulting in a fistula.^{4 6 12 13} Alternatively, as in our case, it can occur spontaneously. The aggressive nature of diffuse large B cell lymphomas and the tendency for adjacent organ invasion contributes to this spontaneous fistula formation.^{9 11} These features were seen in our case where there was extensive infiltration of adjacent organs, including the pancreas and diaphragm.

To our knowledge, there have been only six reported cases of spontaneous gastrosplenic fistula associated with a primary splenic lymphoma.^{5 7–9 16} We report the seventh case of a spontaneous gastrosplenic fistula from a primary splenic non-Hodgkin's lymphoma.

The clinical presentation of diffuse large cell splenic lymphoma usually consists of left upper quadrant abdominal pain accompanied by features of a systemic illness and splenomegaly on examination.⁵ These characteristics were also present in our patient. Furthermore, our patient's admission was complicated with haematemesis, which has been the clinical presentation of other gastrosplenic fistulas.^{6 8}

Multislice CT provides the best imaging modality to identify gastrosplenic fistulas^{10 14} due to excellent spatial resolution and accurate staging of lesions. The clinical presentation of our patient coupled with the absence of any significant past medical history or evidence of endocarditis helped to exclude other differential diagnoses such as necrotising splenic abscess. In previously described cases the spleen was shown to be heterogenous with parenchymal masses containing air, similar to our case.^{8 9} The fistulous tract has been outlined with oral contrast⁷ in some cases. One other case of gastrosplenic fistula in the literature was identified by a retrograde catheter cystography for a suspected splenic abscess that inadvertently revealed itself as a fistula.¹³

Radical surgical resection is the most common treatment option, which would typically demand a splenectomy and gastrectomy. However, there are reports of necessary distal pancreatectomies performed in some cases.¹⁴ Although open procedures are more commonly described, there has been a successful laparoscopic case.¹⁷ An advantage of surgical resection is that it aids in establishing a pathological diagnosis in uncertain cases.¹¹ In contrast, there are also cases of resolution of the fistula with chemotherapy.^{3 18} Patients are at risk of haematemesis due to the risk of invasion into adjacent vasculature, specifically the gastric and splenic vessels. Treatment can also be supportive and in life threatening blood loss interventional radiology in the form of splenic artery embolisation⁸ has been described. Surgery in our patient would have been a huge undertaking with associated high mortality in view of the size of the lesion and multiple adjacent structures involved. The patient was not clinically septic and chemotherapy was therefore the treatment option offered. The presence of fistulas, risk of haemorrhage and infection highlights the challenges faced with managing tumoural fistulas.