Retroperitoneal melanocytic schwannoma

A para-aortic malignant melanotic nerve sheath tumor mimicking a gastrointestinal stromal tumor: a rare case report and review of literature

Background

Malignant melanotic nerve sheath tumor (MMNST), formerly called melanotic schwannoma, is a rare tumor of neural crest derivation which most frequently arises from the region of spinal or autonomic nerves near the midline. Recent studies have reported malignant behavior of MMNST, and there still has no standard management guidelines. Intra-abdominal MMNST, which has never been reviewed as an entity, is even rarer. In this study, we present a rare case of a cystic MMNST arising from the para-aortic region and mimicking an intra-abdominal gastrointestinal stromal tumor (GIST), and review the literature regarding 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.

Novel response to neoadjuvant anti-PD1 therapy for a patient with retrocaval melanotic schwannoma

Melanotic schwannoma is a rare nerve sheath tumor composed of melanin-producing Schwann cells with the potential for metastasis. These tumors can be associated with familial tumor syndromes and can cause significant symptoms related to nerve compression and mass effect. Due to the rarity of these lesions, they can be initially misidentified as melanocytomas, pigmented dermatofibrosarcoma protuberans, neurofibromas or malignant melanomas. Surgical excision is the mainstay of treatment with limited benefit from adjuvant systemic chemotherapy or radiation. Modern treatments with immune checkpoint blockade have demonstrated significant improvements in progression-free and overall survival for a variety of cancer histologies; however, anti-PD1 therapy has yet to be evaluated in patients with melanotic schwannoma. This report demonstrates a significant improvement in symptomatology and tumor stability with neoadjuvant anti-PD1 therapy for a retrocaval melanotic schwannoma initially masquerading as malignant melanoma. This report demonstrates the potential benefit of a novel therapeutic option for patients with melanotic schwannoma.

Laparoscopic resection of a giant retroperitoneal melanotic schwannoma

Background

Retroperitoneal schwannomas are extremely rare, as they account for only 3% of retroperitoneal tumors. Clinical symptoms are nonspecific and of late onset, meaning that these tumors are diagnosed at an advanced stage. Surgical resection is required for histological diagnosis and to prevent possible malignant transformation. Celioscopy offers numerous benefits, reducing postoperative pain and speeding up the patient's return to autonomy, but it can pose a real challenge due to the size of these lesions.

Case presentation

We report a case of laparoscopic resection of a very large right-sided retroperitoneal schwannoma, with a particular histological form.

Conclusion

Surgical resection in a single unit remains the golden rule, and a laparoscopy can be proposed when the diagnosis is beyond doubt. The large size of the retroperitoneal melanotic schwannomas, a common feature, increases surgical difficulties but is not a contraindication to this approach.

Retroperitoneal giant schwannoma eroding lumbal vertebra: A case report with a literature review

A huge schwannoma, located in the retroperitoneal space, is found very rarely. The main purpose of this paper is to present the case of a giant retroperitoneal schwannoma which partly invaded L4 vertebral body. The secondary purpose is to summarize the case-report articles on retroperitoneal schwannomas. A circumscribed heterogenic tumour was revealed on transabdominal sonography. It extended into the right retroperitoneal space. CT and MRI revealed a paravertebral tumour in the size of 11 cm × 9 cm, which is causing a partial lysis of L4 vertebral body (15% of vertebral capacity), expanding intravertebral foramen and filling the right retroperitoneal space. A preoperative core needle biopsy was performed and a benign schwannoma was diagnosed. A complete surgical excision of the tumour was achieved by a two-step operation. During the first step, the neurosurgeons made L4 hemilaminectomy, facetectomy and a transverse process resection by posterior extended approach. The general surgeons excised the residual retroperitoneal part of the tumour by midline transabdominal approach 10 days later. The diagnosis of benign schwannoma was verified histochemically. There were no sign of tumour recurrence or spine destabilization at the six-month follow-up. In conclusion, although majority of giant retroperitoneal schwannomas can be completely removed performing one-step operation, a preoperative consideration about rationality of two-step operation should be mandatory when tumour destructs a part of vertebral body. Our case shows that the combined two stage complete surgical excision of a giant retroperitoneal schwannoma, eroding 15% of L4 vertebra’s osseous capacity, is effective and does not have any negative influence on spinal stability.