A case of cystic lymphatic malformation mimicking acute appendicitis in an adult patient: a rare diagnostic pitfall

Abstract

Abdominal cystic lymphatic malformations are rare pathological entities of uncertain aetiology that usually present in early childhood with indolent abdominal distention. We report the case of a 17-year-old man who presented to our hospital with acute right lower quadrant pain, nausea and anorexia. His blood tests revealed a raised white cell count and elevated inflammatory markers. Clinical examination revealed signs of localised right lower quadrant peritonism. A diagnosis of clinical appendicitis was made, and in keeping with local management protocols, the patient proceeded to theatre for a diagnostic laparoscopy without radiological investigations. Operative findings yielded a normal appendix and a large abdominal cystic malformation. This article highlights the need to keep a broad differential diagnosis when performing surgery on patients with clinically presumed appendicitis and the importance of radiological investigations in clinical decision-making, we also review abdominal cystic lymphatic malformations as a rare diagnostic pitfall.

Background

Acute-onset abdominal pain accounts for a significant proportion of presentations to adult general surgical departments worldwide. Right lower quadrant pain in young and otherwise healthy patients is commonly associated with appendicitis, and diagnostic laparoscopy, in the absence of radiological investigations, is considered appropriate in the setting of a convincing clinical and biochemical picture. Although this practice minimises exposure to ionising radiation and time to definitive treatment, it exposes the treating clinician to unexpected intraoperative findings. Abdominal cystic lymphatic malformations (CLMs) are rare and benign entities that cause symptoms through mass effect and are almost exclusively observed in children.¹ In this article, we report a case of omental CLM mimicking appendicitis in a young adult and discuss the diagnostic pitfall that this rare surgical entity represents.

Case presentation

A 17-year-old high-level male athlete, with no pre-existing medical or surgical history, presented after hours to our emergency department with 24 hours of severe right lower quadrant pain, anorexia and nausea. The patient had a pulse of 64 beats per minute, a blood pressure of 140/60 mm Hg and a respiratory rate of 15 breaths per minute. His oxygen saturation was 100% on room air, and his tympanic temperature was 37.4°C. On examination, he displayed signs of localised peritonism in the right iliac fossa with percussion tenderness, rebound tenderness and a positive Rovsing’s sign. Blood testing revealed a raised white cell count (14.7×10⁹/L), neutrophil count (10.6×10⁹/L) and C reactive protein (39 mg/L). His lipase titre and liver function tests were within normal reference ranges, and his midstream urine was unremarkable.

In keeping with the clinical picture and local management protocols, the patient was consented and taken to theatre for a diagnostic laparoscopy.

On laparoscopic entry of the abdomen, we were confronted with a large amount of intraperitoneal serous fluid and a large cystic structure extending into the right lower quadrant from the upper abdomen. The appendix had a normal appearance and there was no peritoneal disease (figure 1). A midline laparotomy, performed to achieve better access, further revealed the large cystic structure arising from the greater omentum and extending from the lesser sac to the right iliac fossa (figure 2).

Figure 1.

Laparoscopic photos showing the normal appearance of the appendiceal body (A), tip and base (B).

Figure 2.

Intraoperative photos taken at the time of laparotomy showing the anterior (A) and the posterior aspect of the cystic lymphatic malformation (B) suspended in greater omentum.

The intraperitoneal fluid was sampled, and the cyst was resected en bloc by dividing the greater omentum off the greater curvature of the stomach with a Maryland Ligasure device. The appendix was left in situ as the risk of appendicectomy-related infection was thought to be high, given the copious amount of intra-abdominal fluid.

Analysis of the peritoneal fluid demonstrated an amylase titre of 61 U/L, abundant histiocytes, scattered mesothelial cells and neutrophils, and the absence of microorganisms, epithelial cells or malignant cells.

Examination of the surgical specimen revealed two large unilocular cysts attached to the fatty omentum, filled with yellow serous fluid and displaying a smooth brown coloured serosal surface. Their wall thickness measured between 1 mm and 2 mm.

Histopathological analysis (figure 3) showed a thin internal layer of flat cells; a cyst wall composed of fat, smooth muscle and mixed inflammatory cells; and an external layer of reactive mesothelial cells with overlying fibrin. No atypia, papillary architecture, epithelial component or malignant cells were observed.

Figure 3.

Photomicrographs of histopathological slides displaying the cyst wall containing fat, muscle, congested vessels and fibrous tissue (40×) (A); a layer of flattened cuboidal cells lining the cyst (top of cyst wall) (200×) (B); lining cells positive for D2-40 (200×) (C); and lining cells negative for calretinin (200×) (D).

Immunohistochemical staining of the cyst lining was positive for D2-40 but negative for CKAE1/AE3, calretinin, CD68 and CD34.

The final pathology was reported as a CLM.

Outcome and Follow-up

The patient’s postoperative recovery was uneventful and the patient was released from the hospital 4 days after surgery. He was reviewed in an outpatient clinic 1 month after surgery, discharged back to the care of his general practitioner and returned to high-performance sports 3 months later.

Discussion

CLMs or cystic lymphangiomas are rare benign malformations of the lymphatic channels which can affect any part of the body except the brain. They are found in the neck or axilla in 95% of cases, with only 1% affecting the mesentery, greater omentum or retroperitoneum.²

The exact aetiology of CLMs remains uncertain. Two hypotheses coexist and probably describe two distinct disease entities. The first, supported by the fact that 80%–90% of growths are diagnosed in the first few years of life,¹ suggests that CLMs arise from the sequestration of endothelial channels located in the neck, mesentery root and femoral vein bifurcation which normally coalesce between the 12th and 16th week in utero to form lymphatic channels. Their growth over time is thought to be driven by the continuous production and accumulation of fluid and the proliferation of pre-existing spaces.³ The second hypothesis, based on reports of adult-acquired CLMs, suggests that trauma, radiation therapy or surgery-induced inflammation or bleeding in fully formed lymphatic vessels can lead to vessel obstruction and subsequent lymphangioma formation.^{2 4}

Abdominal CLMs usually present as indolent slowly evolving abdominal masses. On rare occasions, however, abdominal CLMs present in the context of acute abdominal pain, usually due to infection, bowel obstruction, haemorrhage or ascites. CLMs have been mistaken for acute appendicitis and gynaecological malignancies in acute presentations.^5–7 The theory that paediatric and adult CLMs represent two different aetiological entities is, in our view, substantiated by the observation that abdominal CLMs presenting as acute abdominal pain are more common in paediatric patients, while adults typically have more protracted symptoms.⁸

Due to their lack of symptoms, abdominal CLMs are usually diagnosed incidentally. In a non-acute presentation with painless abdominal distention or masses, a presumptive diagnosis can be achieved preoperatively with ultrasound or axial imaging. A biopsy is not advised due to reported low yield and the risk of needle tract seeding in the rare case of cystic malignancies.³ In acute presentations, a presumptive diagnosis can be made on emergent preoperative imaging or based on intraoperative findings.⁹

No clear guidelines exist for the treatment of abdominal CLMs, but en bloc surgical resection, when technically feasible, appears to be the favoured therapy as partial resection or aspiration followed by sclerotherapy is associated with high recurrence rates.^{9 10} In neonatal and infant patients, surgery is usually delayed to limit exposure to early general anaesthesia, mechanical ventilation and blood loss unless the lesion is causing pain or bleeding, or compressing and impeding the function of the surrounding organs.

Histopathological analysis of the resected sample provides the definitive diagnosis and excludes other potential cystic lesions such as mesenteric cysts, mesenteric haemangiomas, lymphangiosarcoma, cystic mesotheliomas and retroperitoneal cystic neoplasm. CLMs are histologically classified as hamartomas and usually display a single layer of endothelium overlying a cyst wall containing small lymphoid aggregates, smooth muscle cells and occasional foam cells.

On immunohistochemical staining, D2-40 positivity can be used to identify the lymphatic endothelial component of the mass, while CD34 and CKAE1/AE3 negativity, respectively, rules out a vascular endothelial and epithelial origin. Negative stains for calretinin and CD68 importantly revoke the diagnosis of malignant peritoneal mesothelioma and rare histiocytic tumours. The cyst fluid can be serous, serosanguinous, chylous and occasionally purulent.^{2 11}

In our case, the CLM was an unexpected finding due to the strong clinical suspicion of acute appendicitis. The size of the cyst required conversion to a laparotomy to enable safe resection. Our patient was young and had a preoperative Alvarado score of 7 and and Appendicitis Inflammatory Response score of 7. Accordingly, it would have been appropriate to obtain an ultrasound to confirm the diagnosis of appendicitis prior to proceeding to laparoscopic resection.¹² This additional test, which would have allowed us to identify the patient’s CLM preoperatively and enabled better surgical planning, was not available at the time of the patient’s workup. We maintain our choice to not perform a CT scan on this patient given his age.

The acute presentation in our young adult patient may have been hastened by a cyst rupture and development of acute ascites following his participation in high-level contact sports.

Learning points.

• Surgeons need to keep a wide differential diagnosis in patients undergoing diagnostic laparoscopy for right lower quadrant pain.

• Cystic lymphatic malformations can mimic appendicitis in adult patients.

• Abdominal cystic lymphatic malformations are difficult to diagnose preoperatively due to the lack of specific symptoms, especially when a patient presents with acute abdominal pain.

• Preoperative ultrasound is a relatively cheap and non-invasive investigation that should be performed in intermediate-risk young patients to confirm the diagnosis of acute appendicitis and reveal potential rare mimics.