一例類似胃腸間質瘤的主動脈旁惡性黑色神經鞘瘤－罕見病例報告及文獻回顧

林寬宇¹、陳律臻²、熊小澐³、洪晟鈞^4,5、楊晨洸⁴、陳志榮²、裘坤元^4,6

¹林口長庚紀念醫院,教學部;²台中榮民總醫院,病理檢驗部;³台中榮民總醫院,介入性診療放射科;⁴台中榮民總醫院,泌尿醫學部;⁵中山醫學大學,醫學研究所;⁶國立暨南國際大學,應用化學系

A Para-Aortic Malignant Melanotic Nerve Sheath Tumor Mimicking a Gastrointestinal Stromal Tumor – A Rare Case Report and Review of Literature

Kuan-Yu Lin¹、Lujen Chen²、Siu-Wan Hung³、Sheng-Chun Hung^4,5、Cheng-Kuang Yang⁴、Chih-Jung Chen²、Kun-Yuan Chiu^4,6

¹Department of Medical Education, Chang Gung Memorial Hospital, Linkou Branch, Taoyuan City 333, Taiwan; ²Department of Pathology and Laboratory Medicine, Taichung Veternas General Hospital, Taichung, Taiwan; ³Interventional Radiology, Radiology Department, Taichung Veterans General Hospital, Taichung, Taiwan, R.O.C.; ⁴Department of Urology, Taichung Veterans General Hospital, Taichung, Taiwan, R.O.C.; ⁵Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan, R.O.C.; ⁶Department of Applied Chemistry, National Chi Nan University, Nantou, Taiwan, R.O.C.

Background: Malignant melanotic nerve sheath tumor (MMNST), formerly known as melanotic schwannoma, is a rare tumor derived from neural crest cells. It most commonly originates from the spinal or autonomic nerves near the midline. Recent studies have reported the malignant behavior of MMNST, and there are still no standard management guidelines. Intra-abdominal MMNST, which has never been thoroughly reviewed as a distinct entity, is even rarer. In this study, we present a rare case of a cystic MMNST arising from the para-aortic region, mimicking an intra-abdominal gastrointestinal stromal tumor (GIST), and review the literature concerning MMNSTs located in the abdominal cavity.

Case presentation: A 59-year-old female was incidentally found a tumor located in the left para-aortic area by non-contrast computed tomography. A Magnetic Resonance Imaging showed a cystic mass originated from the inferior mesenteric artery (IMA) territory. A GIST was initially diagnosed. The tumor was resected en bloc by laparoscopic surgery and was found between mesocolon and Gerota’s fascia with blood supply of IMA. Grossly, dark brown materials were noted at the inner surface of the cystic wall. Microscopically, the tumor cells were melanin-containing, and no psammomatous bodies were present. Immunohistochemically, the tumor showed positivity for MART1, HMB45, collagen IV, and SOX10, and negativity for AE1/AE3. MMNST was favored over malignant melanoma, since the tumor was located near ganglia and had cells with less atypical cytology and a low mitotic rate, and subsequent adjuvant radiotherapy was performed. The patient was alive with no evidence of recurrent or metastatic disease 11 months after radiotherapy.

Conclusions: Our review of abdominal MMNST cases showed a female predominance, with an average age of 54.8 years, and a trend toward being a larger tumor showing cystic or necrotic changes. Local recurrence and metastasis rate were reviewed, and both showed a low rate. Diagnosis of MMNST should combine all the available findings, and complete excision of the tumor should be performed, followed by long-term patient monitoring.