Non psammomatous melanocytic schwannoma presenting as a subcutaneous nodule: A rare presentation of a rare lesion

Case Report: Cutaneous melanocytic schwannoma with concomitant melanocytoma in a canine

Schwannoma is a nerve sheath tumour arising from differentiated Schwann cells, and melanocytic schwannoma (MS) is a rare variant where the Schwan cells produce melanin pigment. MS is typically associated with spinal nerve roots and there have been only ~20 reports of cutaneous or subcutaneous MS to-date in humans. In canines, there have only been two reports of MS, both associated with spinal root nerves. In this report, we describe a 7-year-old Weimaraner cross breed dog that presented with two pigmented lesions on the eyelids. The lesions were surgically removed and histological analysis revealed well-circumscribed, non-encapsulated, expansile, neoplasms that were displacing most of the dermis and adnexa. The first lesion was composed of spindloid cells arranged in short interlacing streams with large amounts of pale eosinophilic cytoplasm that sometimes contained fine melanin granules. In areas there were spindle cells arranged in verocay bodies which led to a diagnosis of MS. In contrast, the second lesion was composed of polygonal cells arranged in thick sheets with large amounts of pale eosinophilic cytoplasm that sometimes contained fine melanin granules. The diagnosis was melanocytoma (which is one of the macroscopic differential diagnoses for MS). Whilst melanocytoma is a commonly occurring cutaneous lesion in canines and surgical removal is considered curative, due to little being known about MS in dogs, the outcome remained guarded, as MS in humans has an unpredictable nature, and recurrence and metastasis have been reported.

A Case of Malignant Melanotic Schwannoma of the Trigeminal Nerve: A Case Report and Review of Literature

Intracranial melanotic schwannoma is quite rare, and involvement of the trigeminal nerve is even rarer. Early diagnosis and surgical excision are the mainstays of management. These tumors have a high tendency to recur and there is high possibility of metastasis. Adjuvant radiotherapy should be considered since the prognosis is uncertain. A 23-year-old man started developing numbness over the left side of the forehead 9 months ago that progressed to involve the ipsilateral cheek. The patient started having diplopia on looking to the left side 8 months ago. His relatives noticed a change in his voice 1 month ago and he developed weakness in the right upper and lower limbs, which was gradually progressive. The patient had slight difficulty swallowing. After examination, we found involvement of multiple cranial nerves with pyramidal signs. Magnetic resonance imaging (MRI) was suggestive of an extra-axial lesion in the left cerebellopontine angle extending into the middle cranial fossa, which was having high T1 and T2 signal loss with contrast enhancement. We achieved near-total excision of the tumor via a subtemporal extradural approach. Trigeminal melanotic schwannoma is a rare occurrence constituting melanin-producing cells and Schwann cells. Rapid progression of symptoms and signs should prompt the suspicion of the possible malignant nature of the pathology. Extradural skull base approaches reduce the risk of postoperative deficits. Differentiating melanotic schwannoma from malignant melanoma is of utmost importance in planning of management.

Sporadic spinal psammomatous malignant melanotic nerve sheath tumor: A case report and literature review

Background

Sporadic Spinal Psammomatous Malignant Melanotic Nerve Sheath Tumor (SSP-MMNST) is a rare subgroup of peripheral nerve sheath tumors arising along the spine. Only a few reports of SSP-MMNST have been described. In this paper, we review the literature on SSP-MMNST focusing on clinical, and diagnostic features, as well as investigating possible pathogenetic mechanisms to better implement therapeutic strategies. We also report an illustrative case of a young female presenting with cervicobrachial pain due to two SSP-MMNSTs arising from C5-6 right spinal roots.

Case description

We report a case of a 28-year-old woman presenting with right arm weakness and dysesthesia. Clinical examination and neuroimaging were performed, and, following surgical removal of both lesions, a histological diagnosis of SSP-MMNST was obtained.

Results

The literature review identified 21 eligible studies assessing 23 patients with SSP-MMNST, with a mean onset age of 41 years and a slight male gender preference. The lumbar district was the most involved spinal segment. Gross-total resection (GTR) was the treatment of choice in all amenable cases, followed in selected cases with residual tumor by adjuvant radiotherapy or chemotherapy. The metastatic and recurrence rates were 31.58% and 36.8%, respectively.

Conclusion

Differently from common schwannomas, MMNST represents a rare disease with known recurrence and metastatization propensity. As reported in our review, SSP-MMNST has a greater recurrence rate when compared to other forms of spinal MMNST, raising questions about the greater aggressiveness of the former. We also found that residual disease is related to a higher risk of systemic disease spreading. This metastatic potential, usually associated with primary lumbar localization, is characterized by a slight male prevalence. Indeed, whenever GTR is unachievable, considering the higher recurrence rate, adjuvant radiation therapy should be taken into consideration.

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.

Nevus, melanoma or something else? Mesenchymal neoplasms with melanocytic differentiation

The overwhelming majority of cutaneous neoplasms with melanocytic differentiation are nevi, melanomas and more rarely melanocytomas. Nevertheless, there is also a group of mesenchymal neoplasms with genuine melanocytic differentiation which can create diagnostic difficulties with significant repercussions. These can rarely present as primary or metastatic cutaneous lesions. Theones that are relevant to a dermatopathologist include malignant melanotic nerve sheath tumor, perivascular epithelioid cell neoplasm and clear cell sarcoma. This work will provide a thorough review of clinical presentation, morphologic and immunohistochemical features as well as molecular pathogenesis of these tumors. We hope to familiarize the general dermatopathology readership with a group of neoplasms of mesenchymal lineage exhibiting melanocytic differentiation and ultimately avoid diagnostic misadventures. This article is protected by copyright. All rights reserved.

Extramedullary melanotic schwannoma recurrence in the cervical vertebral arch: a case report and review of the literature

Melanotic schwannoma (MS), a slowly growing nerve sheath tumor, is not a purely benign tumor. MS accounts for less than 1% of all nerve sheath tumors. We herein describe a rare case of MS and present a literature review focusing on the treatment of this disease. Twelve years before presentation at our hospital, a 41-year-old woman was examined because of an 8-month history of neck pain and 6-month history of upper extremity numbness and weakness. She underwent surgery to remove a tumor, and the pathological examination confirmed a diagnosis of MS. Twelve years later, at 53 years of age, the patient presented to our hospital with a 2-year history of neck pain and upper extremity numbness and weakness. Posterior cervical tumor resection was performed along with posterior cervical laminectomy, decompression and intraspinal space-occupying internal fixation, and radiotherapy. MS recurrence was confirmed. No tumor recurrence or metastasis was found after 7 months of follow-up. Recurrence of MS is rare, and its diagnosis depends on pathological features. Radical excision is the primary treatment for MS. Incomplete resection of MS is a risk factor for postoperative recurrence and metastasis. Furthermore, postoperative adjuvant radiotherapy should be performed to prevent recurrence and metastasis of MS.

Hemorrhagic spinal melanotic schwannoma presenting as acute chest pain: A case report and literature review

Background:

Melanotic schwannoma (MS) is a rare variant of peripheral nerve sheath tumor. MS commonly arises along the spinal nerve sheath. Patients most often experience pain along the dermatome of the affected nerve root. Symptoms development is usually insidious. About half of MS cases are associated with Carney complex, a multi-neoplastic disorder. The remaining cases arise spontaneously. About 10–44% of these tumors undergo malignant transformation.

Case Description:

We describe a case of hemorrhagic MS presenting as acute chest pain mimicking myocardial infarction, a presentation which has not yet been described in the literature. Neurologic examination did not reveal any abnormalities. Myocardial infarction was ruled out in the ER, and a chest CT angiogram was ordered for evaluation of PE or aortic dissection which revealed an intradural extramedullary dumbbell-shaped mass extending through the left vertebral foramen at the level of T8. MRI revealed a heterogenous mass that was hyperintense with T2 and hypointense with T1-weighted imaging. The patient underwent an open laminectomy of the left T8 and T9 vertebrae and gross total resection (GTR) of a hemorrhagic black tumor. Microscopic examination showed fascicles and nests of plump spindle cells with variable intracellular melanin. Immunohistochemistry showed the cells to be positive for S100, SOX10, HMB-45, and MART-1, confirming diagnosis of MS. Two months after the operation, the patient was doing well and is free of recurrence.

Conclusion:

GTR is considered the optimal treatment for MS; radiotherapy and chemotherapy may be considered but have not been shown to improve patient outcomes.

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.

A Rare Case of Hemorrhagic Melanotic Schwannoma in a 38-year-old Female

Melanotic schwannoma is a rare form of nerve sheath tumor composed of melanin-producing neoplastic Schwann cells. Less than 200 cases have been reported worldwide. The entity has been associated with Carney complex, a rare genetic disorder characterized by multiple benign tumors. A 38-year-old female presented to our unit with sudden-onset lower back pain and radiculopathy triggered by a mechanical injury. Imaging demonstrated a lesion within the left L5/S1 neural exit foramen with remodeling of bony architecture typical of a chronic, benign process. She proceeded for resection and histology revealed a psammomatous melanotic schwannoma. The patient recovered well with improvement in symptomology. Due to the aggressive nature of the disease, she remains under surveillance for local recurrence and distant metastasis. Clinicians should be aware of this malignant entity, despite its possible presentation with radiological features of a chronic, benign process. Unusual characteristics such as hemorrhage should be treated with a high index of suspicion.

Melanotic Schwannoma of the Vagina: A Report of a Very Rare Tumor and Review of the Literature

Melanotic schwannoma (MS) is a rare nerve sheath tumor with fewer than 200 cases reported. MS has uncertain malignant potential and comprises 1% of all nerve sheath tumors with a predilection for the spinal nerve roots. An even rarer location for this tumor is the vagina. Up to 55% of MSs that contain psammoma bodies are associated with the Carney complex, an autosomal dominant syndrome. Criteria for malignancy in MS are still not well established and long term follow-up of patients is recommended. A 26-year-old woman presented with a bleeding vaginal tumor which was diagnosed as MS following excision. The clinical, histopathological, and immunohistochemical features of this tumor are discussed.

Pathology of Melanotic Schwannoma

CONTEXT.—

Melanotic schwannoma (MS) is a nerve sheath tumor with a uniform composition of variably melanin-producing Schwann cells and metastatic potential. The MS is an uncommon neoplasm, accounting for less than 1% of all nerve sheath tumors, with a predilection for spinal nerve involvement. Microscopically, the tumors are characterized by spindle and epithelioid cells arranged in interlacing fascicles, with marked accumulation of melanin in neoplastic cells and associated melanophages. The MSs are frequently associated with Carney complex, showing features of psammoma bodies and adipose-like cells. Strict criteria of malignancy in MS are not well developed, although a combination of worrisome histologic features (large, vesicular nuclei, with macronucleoli, brisk mitotic activity, and necrosis) raises concern for aggressive behavior.

OBJECTIVE.—

To review the current status of the MS literature, discussing putative etiology, histopathology, current genetics, and differential diagnoses, including overlap with other pigmented tumors.

DATA SOURCES.—

Search of PubMed (National Center for Biotechnology Information, Bethesda, Maryland) and the authors' own experiences.

CONCLUSIONS.—

The occurrence of MS at several unusual anatomic sites and its spectrum of morphologic patterns can result in significant diagnostic difficulty, and correct diagnosis is particularly important because of its high tendency to recur locally and to metastasize, which highlights the importance of diagnostic recognition, ancillary molecular genetic testing, and close clinical follow-up of patients with MS.