罕見後腹腔腫瘤不典型的臨床表現:案例分享
柯旭承¹、莊毓峰¹、許兆畬¹、歐宴泉¹、童敏哲¹、薛冠群²、高鴻偉³

童綜合醫療社團法人童綜合醫院 外科部 泌尿科

童綜合醫療社團法人童綜合醫院 外科部 一般外科

童綜合醫療社團法人童綜合醫院 病理部

Rare Retroperitoneal tumor with atypical clinical presentation – a case sharing

Hsu-Cheng Ko¹、 Yu-Feng Chuang¹、 Chao-Yu Hsu ¹、Yen-Chuan Ou¹、Min-Che Tung¹、Kuan-Chun Hsueh²、Hong-Wei Gao³

¹ Division of Urology, Department of Surgery, Tungs' Taichung MetroHarbor Hospital, Taichung City, Taiwan

²Division of General Surgery, Department of Surgery, Tungs' Taichung MetroHarbor Hospital, Taichung City, Taiwan

³Department of Pathology and Laboratory Medicine, Tungs' Taichung MetroHarbor Hospital, Taichung City, Taiwan

Introduction

Adrenal schwannoma is a very rare and mostly benign retroperitoneal tumor with an incidence rate of 0.48 percent of all adrenal tumors. Due to its slow-growing nature, patients with adrenal schwannoma are often asymptomatic until it grows large enough to exert mass effect on adjacent tissue. Herein, we introduce a case of one unprecedentedly giant adrenal schwonnoma.

Case presentation

This 39-year-old male, with history of hypertension, visited our outpatient department and presented with abdominal fullness, epigastric pain, and had have one palpable huge mass over left upper abdomen for several months. Except for mildly impaired renal function, there was no major abnormal finding on hemogram and biochemistry. Abdominal computed tomography (CT) showed a giant left cystic lesion, larger than 25 cm in the greatest diameter, with mural soft tissue component in the left suprarenal region (Figure 1A and 1B) and heterogeneous contrast enhancement in the venous and the delayed phase. Technetium-99m mercaptoacetyltriglycine (Tc-99m MAG3) indicated poor left renal function.

The patient received laparotomy for excision of left retroperitoneal tumor and partial nephrectomy. We made a L-shaped incision from subxiphoid area to above the level of the umbilicus and extended to the left flank area (Figure 2A).  Many feeding vessels to the giant tumor were found and ligated (Figure 2B). A total of 15 liters brownish fluid was drained during this operation. The measured blood loss was 250 ml. Final pathologic results of the resected tumor revealed alternating compact hypercellular Antoni A areas and hypocellular Antoni B areas, and diffusely positive for S-100 protein, confirming the diagnosis of schwannoma. Postoperatively, the patient has been free of tumor recurrence for 8 months so far.

Discussion

Benign schwannomas are rarely seen in the retroperitoneum, with an incidence rate of 0.7–2.7% of all retroperitoneal tumors. Malignancy accounts for 70–80% of primary retroperitoneal soft-tissue tumors.

Adrenal schwannomas are slow-growing; hence, asymptomatic status persisted until the tumor is large enough to exert mass effects on adjacent tissues, resulting in abdominal distension and vague abdominal or back pain. Therefore, adrenal schwannomas are often diagnosed at a large size and are seldom found at a small size. Other atypical presentations include headache, secondary hypertension, and renal colic pain with hematuria, which may be related to tumor compression of the upper urinary tract.

Owing to cystic changes, calcification, septation, hemorrhage, and secondary degenerative changes, adrenal schwannomas often present as heterogeneous masses with circumscribed, round, or oval shapes on multiphase CT and magnetic resonance imaging (MRI). Despite these accurate imaging techniques, it is difficult to differentiate adrenal schwannomas from other malignant tumors, such as liposarcoma, adrenocortical carcinoma, pheochromocytoma, ganglioneuroma, and other metastatic lesions. The final diagnosis was based on the pathological report. Histologically, schwannomas comprise spindle-shaped cells with ovoid-to-wavy nuclei and alternating compact hypercellular Antoni A areas and hypocellular Antoni B areas. Immunohistochemically, S-100 protein is a reliable marker for the diagnosis of schwannomas and is especially prevalent in Antoni A areas.

Meticulous preoperative evaluations and experienced surgeons are required to perform resection of giant retroperitoneal tumors. Large retroperitoneal schwannoma occupies a large space in the abdominal cavity, which causes the compression of nearby tissues and organs; therefore, the remaining space to expose is small, making the operation difficult. In most of the studies on laparoscopic resection of adrenal schwannoma, the maximal tumor diameter was < 10 cm, and intraoperative hemorrhage was a major concern because of the rich vessel supply to the tumor. In our case, meticulous hemostasis was performed because of many feeding arteries to the tumor, and appropriate monitoring of fluid drainage was necessary to observe the possible postoperative bleeding or focal abscess formation.

Conclusion

Adrenal schwannoma is a rare and slow-growing retroperitoneal tumor. In most cases, asymptomatic status persisted until the tumor grows large enough to cause pressure on adjacent organs. Most adrenal schwannoma showed great prognosis after radical resection.  Thus, preoperative evaluations, experienced surgeons, and postoperative monitoring are all essential for great postoperative course.