Perforated appendicitis with an associated mucinous tumour

Clinical History

82-year-old female patient institutionalised in the context of advanced dementia, Parkinson's disease and ischaemic stroke was referred to the emergency department for abdominal pain and sepsis. History and physical examination were extremely limited. Laboratory findings showed leucocytosis at 14.2 G/l with left shift and C-reactive protein at 189.

Imaging Findings

An injected portal phase abdominal CT was performed, the CT showed a discretely enlarged appendix measuring 7mm in diameter with a discontinuity of the mucosa at its extremity, diffuse peritoneal enhancement and ascites in moderate quantity. The examination also showed a mass at the root of the mesentery measuring 11x5cm in the axial plane with retro-peritoneal infiltration. The left renal vein was laminated but still permeable. This mass was suspected to be a lymphoma despite the concomitant findings. There was a reflex ileus with small bowel measuring up to 3.4cm in diameter with thickened walls.

Discussion

Emergency laparoscopy was performed showing perforated appendicitis with purulent peritonitis and 1.5 L of purulent liquid was removed. Histology of the appendix showed a low grade mucinous tumour associated with perforated acute appendicitis.

The initial CT scan showed diffuse peritoneal enhancement, purulent peritonitis due to perforated appendicitis was considered the most likely cause. Although a component of peritoneal lymphoma or dissemination of the appendiceal tumour could not be formally excluded, analysis of the peritoneal liquid showed no atypical cells.

Further investigations, including flow cytometry of a peripheral blood sample, showed diffuse B-cell lymphoma, this meant that the mesenteric mass could be either linked to the appendicitis or lymphoma. Biopsy of the mass was not performed due to the diminished status of the patient and clinical follow-up was warranted which showed persistence of the mesenteric mass in favour of lymphoma.

The most frequent primary tumours of the peritoneum, mesentery and omentum are mesothelioma and sarcomas and the most frequent secondary tumours include stomach, ovarian and colonic tumours. Despite lymphoma being a rare cause, its diagnosis is important due to the possibility of non-surgical treatment [1]. The imaging findings of lymphoma include peritoneal thickening with smooth or nodular diffuse contrast enhancement [2], ascites, omental and mesenteric masses, lymphoadenopathy and organomegaly of the liver and spleen [1]. The most common type of lymphoma is diffuse B-cell lymphoma, as in our case [1, 2]. Imaging findings are not specific, rendering it a diagnostic challenge. Peritoneal lymphomatosis can mimic diffuse carcinomatosis or infectious tuberculous peritonitis, contrary to these aetiologies, ascites in peritoneal lymphomatosis does not present with any loculations or septations [2].

Primary appendiceal tumours are found in less than 2% of surgically removed appendices [3, 4, 5]. Mucinous tumours can cause cystic dilation of the appendix due to mucin accumulation and may disseminate in the peritoneal cavity forming mucinous ascites known as pseudomyxoma peritonei [3]. CT imaging may show an appendiceal mucocele which appears as a round, low-density, encapsulated mass in continuity with the caecum [5]. Curvilinear mural calcifications are highly suggestive but present in less than 50% of cases [5]. Pseudomyoma peritonei is extremely rare, about 1-2 million cases per year [5]. It appears as multicystic masses with septa or thickened walls, punctuate mural or curvilinear calcifications may be present. Treatment includes cytoreductive surgery in combination with hyperthermic intraperitoneal chemotherapy [6]. Appendiceal tumours pose a diagnostic and surgical challenge as pre-operative iatrogenic spread must be avoided.

Differential Diagnosis List

Final Diagnosis

1. Acute perforated appendicitis with low-grade mucinous neoplasm2. Lymphoma

URL:	https://eurorad.org/case/10592
DOI:	10.1594/EURORAD/CASE.10592
ISSN:	1563-4086