Paravertebral retroperitoneal ancient schwannoma mimicking irritable bowel syndrome

Abstract

We report a case of paravertebral retroperitoneal ancient schwannoma (RPAS) with symptoms suggestive of irritable bowel syndrome that was relieved after resection. Very few cases have been reported of RPAS with gastrointestinal symptoms. Increased bowel activity associated with RPAS has not been reported. Our case report suggests that RPAS may present with increased bowel frequency that could be relieved after surgical resection.

Introduction

We report a case of retroperitoneal ancient schwannoma (RPAS) arising paravertebrally from the ventral rami of the second lumbar nerve. The symptoms were mimicking that of an irritable bowel syndrome [1], which was relieved following resection of the tumour. There are many case reports and reviews of RPAS [2–6]. However, extremely few cases of RPAS that presented with gastrointestinal symptoms have been reported [2, 7–9]. Around 1% of schwannomas occur in the retroperitoneum and less than 1% of soft tissue tumours are ancient schwannomas [10]. Most RPAS are asymptomatic, have typical histopathology, are treated by resection and rarely become malignant [11, 12]. The differential diagnosis is listed in Table 1 [12].

Case report

A man in his 30s presented with symptoms suggestive of irritable bowel symptoms with increased bowel movements coinciding with the onset of colicky abdominal pain for the past 8 months. The bowel movements relived his pain and had no remission from his symptoms. He had no relevant medical comorbidities in the past. The patient had normal vitals. There were no physical exam abnormalities except for a slight fullness in the left renal angle (Fig. 1). There was nothing significant on a rectal examination. An X-ray of the chest showed normal findings. Blood investigations showed: haemoglobin 130 g/l, total leukocyte: 7.4 × 10⁹/l, serum creatinine 0.52 mg/dl, fasting blood sugar 90 g/dl, alanine transaminase 26 U/L, aspartate transaminase 42 U/L, alkaline phosphatase 32 U/L and total bilirubin 0.8 mg/dL. Ultrasonography showed a 10-cm mass, with mixed echogenicity. Posterior to the left kidney. Colonoscopy was normal. An abdominal CT scan showed a paravertebral tumour with peripheral enhancement and heterogenous contrast within the tumour (Fig. 2). The tumour showed high intensity on a T2-weighted MRI (Fig. 3). The left kidney and colon were displaced anteriorly. Fine-needle aspiration biopsy was inconclusive. The clinical diagnosis was a retroperitoneal schwannoma. On laparotomy, the left colic vessels appeared to be splayed by the tumour (Fig. 4). The tumour 11 × 6 × 3 cm³ (Fig. 5), which seems to be arising from the L2 nerve, was resected completely (Fig. 6). The patient had no sensory or motor loss postoperatively. He was discharged without complications on the 10th postoperative day. His colonic symptoms had disappeared after surgery. The gross appearance of the resected tumour showed cysts and haemorrhage patches (Fig. 7). Histopathology showed areas of hypercellularity (Antony A) and hypocellularity (Antony B) with degenerative changes leading to nuclear atypia and cystic spaces, typical of an ancient schwannoma (Figs 8–11). Immunohistochemistry with S-100 was positive (Fig. 12). He was devoid of digestive symptoms or radiological evidence of recurrence at 12 months.

Discussion

There are three reports of RPAS who presented with constipation that were relieved after resection [2, 7, 9]. In another case, a patient presenting with endoscopically proven colitis had RPAS that was relieved after resection [8]. The authors’ hypothesized that vascular congestion of the colon could have been a reason for the association of colitis with RPAS [8]. Indeed, in our case, the colic vessels were splayed (Fig. 4). We report for the first time a case of increased bowel movements mimicking irritable bowel syndrome that was relieved after resection of the RPAS. The lack of remission of the patient’s lower abdominal symptoms precludes a definitive diagnosis of IBS.

References