Melanotic schwannoma: an 11-year case series

Malignant Melanotic Nerve Sheath Tumor of the Parotid Gland: A Case Report and Literature Review

Malignant melanotic nerve sheath tumor (MMNST) is a rare and aggressive peripheral nerve sheath tumor of Schwann cell origin that produces differentiated melanin and is clinically misdiagnosed as malignant melanoma. MMNST is most commonly observed in middle-aged adults and is often found in the midline of the spinal nerve or in the peripheral nerve area. It often manifests itself as a localized mass and/or nervous system involvement. To date, no standard guidelines are available for the treatment of MMNST. Herein, we reported a new case of MMNST that occurred in the parotid gland and reviewed the literature for pathological reports on its association with the oral cavity.

The "Pigmented Side" of Nerve Sheaths: Malignant Melanotic Nerve Sheath Tumor

Malignant melanotic nerve sheath tumor (MMNST) represents a highly aggressive neoplasm arising both in peripheral and cranial nerves. It accounts for < 1% of all nerve sheath tumors, but the real incidence may not be well defined yet because of the evolution of its nomenclature. To date, it is considered a distinct tumor type, no longer as the pigmented variant of schwannoma, with a different clinical course and biological behavior. MMNSTs exhibit a specific genetic hallmark related to the PRKAR1A gene, which explains the major incidence in Carney Complex-affected patients. One of the more frequent localizations is the paravertebral region, where it poses diagnostic concerns with both primary tumors arising from soft tissues and the meningeal covering, as well as metastatic ones (ie, melanoma). Herein we present a patient with an MMNST accompanied by the main clinical, radiological, histopathological, and molecular findings, stressing the need for a multidisciplinary diagnostic approach. To the best of our knowledge, this is the first report of proton beam therapy for MMNST. We also performed a literature review to collect and compare the more recent data in English literature and to highlight the "keep-in-mind" concepts to apply in a multidisciplinary diagnostic algorithm, with a focus on histopathology and related pitfalls.

Malignant melanotic schwannoma of the cervical spinal cord: a case report

Spinal cord malignant melanotic schwannoma (MMNST) is a rare central nervous system tumor that originates from the spinal cord or spinal myelin sheath cells and can produce melanin. This type of tumor is usually highly aggressive and malignant, with a poor prognosis. The clinical manifestations of spinal cord MMNST are mainly pain, paresthesia, muscle weakness, muscle atrophy, etc., and symptoms of spinal cord compression, such as intestinal and bladder dysfunction, paraplegia, etc. Early detection of tumor lesions can facilitate tumor removal, improve patients' quality of life, and prolong patients' survival. In this case report, a 27-year-old young woman was diagnosed with MMNST of the cervical spinal cord due to weakness of her limbs in our hospital, and underwent surgical resection. The patient's limbs returned to normal after surgery. It is worth mentioning that the patient visited our hospital 7 months ago for "right upper limb pain for 3 days" and was diagnosed with a cervical spine space-occupying lesion at the same position this time, but the pathology report was "hemosiderosis". The patient's limbs returned to normal after surgery. It is worth mentioning that the patient visited our hospital 7 months ago for "right upper limb pain for 3 days" and was diagnosed with a cervical spine space-occupying lesion at the same position this time, but the pathology report was "hemosiderosis". This case report aims to raise awareness of the problem of spinal cord MMNST and contribute to greater knowledge of this rare tumor. This case report aims to raise awareness of the problem of spinal cord MMNST and contribute to greater knowledge of this rare tumor.

Peripheral nerve tumors

The chapter is focused on the neoplastic peripheral nerve lesions, which primarily involve "cranial and paraspinal nerves," as outlined in the CNS volume (WHO_Classification_of_Tumours_Editorial_Board, 2021). These include classic peripheral nerve sheath tumors such as schwannoma, neurofibroma, intraneural perineurioma, and malignant peripheral nerve sheath tumors, with their variants as well as new and more precisely defined entities, including hybrid nerve sheath tumors and malignant melanotic nerve sheath tumor (previously melanotic schwannoma).

Malignant Melanotic Nerve Sheath Tumors: A Review of Clinicopathologic and Molecular Characteristics

Malignant melanotic nerve sheath tumor (MMNST) which was formerly known as melanocytic schwannoma, is an uncommon aggressive type of nerve sheath tumor. It originates from nerve roots with clonal Schwann cell proliferation and melanin pigment production. MMNST which was once thought to be a benign tumor is now considered a malignant disease based on the latest 2020 World Health Organization classification of soft tissue tumors. Interestingly, despite the histologic features appearing benign with a low proliferation index, the clinical course of this tumor is malignant, which was demonstrated in case series with high rate of recurrences and metastasis. This tumor can occur sporadically or in patients with an underlying familial predisposition syndrome called, Carney's complex. Affected patients will often harbor a germline mutation in the PRKAR1A gene. MMNST can be histologically difficult to distinguish from malignant melanoma, other melanocytic tumors, and Schwannoma. Having a better understanding of its clinic pathologic characteristics and associated conditions is essential in properly diagnosing and managing affected individuals. This includes the possible need for genetic testing to detect germline mutations, genetic counseling, and surveillance according to published recommendations. In this article, we summarize the clinic pathologic and molecular features of MMNST and discuss what is known about its molecular biology and its associations with predisposing conditions. The review was conducted through an extensive PubMed search using keywords then relevant publications were selected.

Primary Malignant Melanotic Nerve Sheath Tumour of the Neck: A Diagnostic Predicament

Primary malignant melanotic nerve sheath tumours, previously called Melanotic schwannomas are rare pigmented tumours of nerve sheath origin, with unspecified biologic behaviour and uncommon presentation in the head and neck region. A primary melanotic schwannoma of the cervical sympathetic plexus, mimicking a cervical lymphadenopathy requires careful evaluation and planning for an optimal outcome. The management of these neoplasms is still controversial, and hence we present a case report with insight into the diagnostic dilemma in work-up of a neck mass that turned out to be a Primary Malignant Melanotic Schwannoma arising from the cervical sympathetic plexus along with a review of literature.

Diagnosis and Treatment of Peripheral and Cranial Nerve Tumors with Expert Recommendations: An EUropean Network for RAre CANcers (EURACAN) Initiative

The 2021 WHO classification of the CNS Tumors identifies as "Peripheral nerve sheath tumors" (PNST) some entities with specific clinical and anatomical characteristics, histological and molecular markers, imaging findings, and aggressiveness. The Task Force has reviewed the evidence of diagnostic and therapeutic interventions, which is particularly low due to the rarity, and drawn recommendations accordingly. Tumor diagnosis is primarily based on hematoxylin and eosin-stained sections and immunohistochemistry. Molecular analysis is not essential to establish the histological nature of these tumors, although genetic analyses on DNA extracted from PNST (neurofibromas/schwannomas) is required to diagnose mosaic forms of NF1 and SPS. MRI is the gold-standard to delineate the extension with respect to adjacent structures. Gross-total resection is the first choice, and can be curative in benign lesions; however, the extent of resection must be balanced with preservation of nerve functioning. Radiotherapy can be omitted in benign tumors after complete resection and in NF-related tumors, due to the theoretic risk of secondary malignancies in a tumor-suppressor syndrome. Systemic therapy should be considered in incomplete resected plexiform neurofibromas/MPNSTs. MEK inhibitor selumetinib can be used in NF1 children ≥2 years with inoperable/symptomatic plexiform neurofibromas, while anthracycline-based treatment is the first choice for unresectable/locally advanced/metastatic MPNST. Clinical trials on other MEK1-2 inhibitors alone or in combination with mTOR inhibitors are under investigation in plexiform neurofibromas and MPNST, respectively.

The Recent Advances in Molecular Diagnosis of Soft Tissue Tumors

Soft tissue tumors are rare mesenchymal tumors with divergent differentiation. The diagnosis of soft tissue tumors is challenging for pathologists owing to the diversity of tumor types and histological overlap among the tumor entities. Present-day understanding of the molecular pathogenesis of soft tissue tumors has rapidly increased with the development of molecular genetic techniques (e.g., next-generation sequencing). Additionally, immunohistochemical markers that serve as surrogate markers for recurrent translocations in soft tissue tumors have been developed. This review aims to provide an update on recently described molecular findings and relevant novel immunohistochemical markers in selected soft tissue tumors.

Magnetic resonance imaging features and clinical course of malignant melanotic nerve sheath tumors: single institution experience over two decades

OBJECTIVE

To evaluate MR features and clinical course of malignant melanotic nerve sheath tumor (MMNST), previously known as melanotic schwannoma and considered indolent and rarely metastasizing.

MATERIALS AND METHODS

This IRB-approved retrospective study searched 31 patients (20 male: 11 female, mean age 48; range 15-76) with histologically confirmed MMNST in a single tertiary cancer center over 22 years. Pre-treatment MR was available in 12 patients and evaluated by two radiologists in consensus regarding lesion location, size, morphology, signal characteristics, contrast enhancement, local invasion, and presence of classic signs of peripheral nerve sheath tumors. Clinical outcomes, including local recurrence, metastasis, and survival, were examined in 12 patients for whom follow-up was available.

RESULTS

The spine was the most frequent site (13/31) among all identified cases. In 12 cases with MR, lesions were well-circumscribed in 11/12 cases, with a mean size of 4.5 cm (2.3-13.0 cm). Ten of 12 cases showed T1 hyperintensity. In 5/9 spinal MRI, tumor involved multiple levels. All lesions showed contrast enhancement, and local bone invasion in > 50%. A dumb-bell shape was common to all spinal lesions. Classical signs of nerve sheath tumors were uncommon. Among 12 patients with a mean follow-up of 4.8 years (range 1.3-10.2 years), six were disease-free, while two had recurrence or metastases, and four had died of metastases.

CONCLUSION

MMNST usually presents as a T1 hyperintense enhancing dumb-bell shaped mass in the spine. Multi-level involvement and bone invasion are common. MMNST is clinically aggressive with high rates of metastases and death.

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.

Malignant psammomatous melanotic schwannoma mimicking adrenal cyst: case report

Background

Melanotic schwannoma is a melanin producing nerve sheath tumors. Rarely, it can be associated with psammoma bodies, called psammomatous melanotic schwannoma. Psammomatous melanotic schwannomas are associated in up to 10% of the cases with Carney’s syndrome. The rarity of the lesion, which may present at different localizations create difficulty in placing a correct initial diagnosis. Definitive diagnosis is made after complete tumor excision and pathomorphological evaluation. The prognosis depends on the anatomical localization, local invasion and presence of a high mitotic index. The main pathomorphological differential diagnosis includes schwannomas and other melanin producing tumors as melanoma.

Case presentation

We present a case of an 11-year-old female with cystic lesion adjacent to right adrenal gland, mimicking adrenal cyst. Ultrasound guided biopsy was undertaken due to the cystic appearance of the formation and the lack of certain diagnosis from the non-invasive diagnostic tests. No signs of cellular and nuclear atypism were observed. The diagnosis of benign endothelial cyst with spontaneous hemorrhage was suggested. The patient underwent transabdominal laparoscopic adrenalectomy en-bloc with the cyst to prevent spillage of the cyst content due to the intimate adhesion of the lesion to the adrenal gland and vena cava inferior. Pathomorphological examination revealed malignant psammomatous melanotic schwannoma. The adrenal gland was intact with no tumor infiltration. The patient was followed up on the 1st and 2nd month afterwards the surgery by MRI with no signs of local recurrence and postoperative complications.

Conclusion

Psammomatous melanotic schwannoma near adrenal gland are rare and present difficulty with exact preoperative diagnosis. Complete resection should always be provided. Laparoscopic surgery is feasible if radical excision is not compromised. Long-term follow-up and Carney’s syndrome surveillance after complete excision are recommended especially in young patients.

Malignant Melanotic Nerve Sheath Tumor

Malignant melanotic nerve sheath tumors are uncommon pigmented tumors of Schwann cell origin, most often found along the spinal nerves. Although well-described in the literature, the tumors are quite rare, making up <1% of nerve sheath tumors. Physicians are, therefore, often unfamiliar with both the appearance and the optimal treatment of such tumors. Morphologically, many imaging features overlap with schwannomas and neurofibromas. Nevertheless, the malignant melanotic nerve sheath tumors are crucial to identify. They can be extremely aggressive, and the management of these tumors is considerably different from their benign counterparts. In this radiology-pathology review, we will highlight the imaging appearance, histologic features, surgical resection, and subsequent therapeutic strategies in a patient with a lumbar malignant melanotic nerve sheath tumor.

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.

Update on MR Imaging of Soft Tissue Tumors of Head and Neck

This article reviews soft tissue tumors of the head and neck following the 2020 revision of WHO Classification of Soft Tissue and Bone Tumours. Common soft tissue tumors in the head and neck and tumors are discussed, along with newly added entities to the classification system. Salient clinical and imaging features that may allow for improved diagnostic accuracy or to narrow the imaging differential diagnosis are covered. Advanced imaging techniques are discussed, with a focus on diffusion-weighted and dynamic contrast imaging and their potential to help characterize soft tissue tumors and aid in distinguishing malignant from benign tumors.

A CHALLENGING CASE OF SPORADIC MELANOCYTOMA OF THE JUGULAR FORAMEN

BACKGROUND

The jugular foramen (JF) can be the site of several tumours. Paragangliomas, schwannomas and meningiomas are the most commonly reported. We describe a case of melanocytoma originating from the JF and presenting with an accessory nerve palsy. Illustrative case: A 48-year-old woman presented with a 6-month history of cervical and left shoulder pain with wasting and weakness of the left trapezius. A Magnetic Resonance Imaging (MRI) showed a T1-hyperintense, T2-isointense, heterogeneously enhancing lesion involving the left JF and extending into the cerebello-medullary and cerebello-pontine cisterns. A retrosigmoid craniotomy was performed and a near total removal achieved. The accessory nerve was involved by tumour and could not be preserved. Given the diagnostic uncertainty between melanotic schwannoma, metastatic melanoma and meningeal melanocytoma, next generation sequencing and genome-wide DNA methylation arrays were performed, documenting a mutation in GNA11 (c.6226A>T, p. Gln209Leu) and a methylation profile consistent with melanocytoma. The patient underwent adjuvant fractionated radiotherapy of the tumour remnant. A follow-up MRI 4 years after surgery did not show any tumour recurrence.

CONCLUSIONS

The differential diagnosis of skull base pigmented tumours can be challenging, particularly when they occur in unusual locations such as the JF. They can be misdiagnosed given their similar clinical, neuroradiological and pathological features if anatomy of the site of origin is not carefully considered and molecular tests are not performed, leading to erroneous treatment and follow up planning.

Can Discord Domain-Containing Receptor 2 Mutation Act as a Disease Modifier for PRKAR1A Associated Melanotic Schwannoma?

Melanotic Schwannomas are rare neural sheath tumors with distinctive findings of both Schwann cells and melanocytic cells. Recognition of this entity has prompted the importance of distinction from similar tumor types such as melanomas. Early diagnosis facilitates removal of the mass with less risk of local invasion and metastasis. Although previously known as mostly benign lesions, malignant conversion and recurrence are recognized. This paper presents a patient with melanotic schwannoma, describes the distinctive features that will separate it from melanoma, and addresses the possibility of further guided therapy through next-generation sequencing.

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.

Psammomatous melanotic schwannoma - a rare neck lump

This case report discusses a cervical psammomatous melanotic schwannoma - a rare form of peripheral nerve sheath tumour - which may be highly vascular and is often associated with the Carney complex. Significant intraneural bleeding, which was encountered intraoperatively, was controlled successfully with a gelatine-based thrombin haemostatic agent (Floseal^®, Baxter International, Deerfield, IL, USA) without complication.

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.

Updates from the 2020 World Health Organization Classification of Soft Tissue and Bone Tumours

The fifth edition of the World Health Organization (WHO) classification of soft tissue and bone tumours was published in May 2020. This 'Blue Book', which is also available digitally for the first time, incorporates an array of new information on these tumours, amassed in the 7 years since the previous edition. Major advances in molecular characterisation have driven further refinements in classification and the development of ancillary diagnostic tests, and have improved our understanding of disease pathogenesis. Several new entities are also included. This review summarises the main changes introduced in the 2020 WHO classification for each subcategory of soft tissue and bone tumours.

Extramedullary malignant melanotic schwannoma of the spine: Case report and an up to date systematic review of the literature

BACKGROUND

Melanotic schwannoma is a rare variant of schwannoma. Extramedullary melanotic schwannoma originates in the vicinity of nerve roots mimicking other intervertebral disc disorders. Therefore, T1 and T2-weighted MRI sequences become an essential tool for diagnosis. Aside from case reports, no large studies exist to provide consensus on the signal intensities in T1 and T2-weighted MR imaging. Moreover, no clear evidence is available to delineate prognosis. Here, a case report is presented together with a subsequent systematic review of the literature regarding this rare entity.

CASE DESCRIPTION

A 45-year old female presented with a one-year history of insidious onset of neck pain and paraesthesia. Magnetic resonance imaging confirmed an extramedullary lesion along the C6 nerve root with T1-weighted hyperintensity and T2-weighted hypointensity. Despite two surgical decompressions and adjuvant immunotherapy, the patient unfortunately passed away due to metastatic progression.

DISCUSSION

According to the systematic review conducted, in over half of the cases of extramedullary melanotic schwannoma, there is local reoccurrence and/or distal metastasis. Moreover, in 64.7% and 70.6% of the cases, the T1-weighted image of the lesion appears hyperintense and hypointense on a T2-weighted image, respectively. It is an aggressive variant of schwannoma, one of the most commonly observed extramedullary tumours presenting to neurosurgical practice.

CONCLUSION

Our results highlight that specific T1 and T2-weighted imaging findings can provide valuable information, enabling early suspicion, influencing the surgical aims and strategy and the timely commencement of relevant immunotherapy. Considering the poor prognosis, early adjuvant therapy with other modalities should be considered.

Intrapelvic melanocytic schwannoma resection with computer-assisted navigation

Melanocytic schwannoma is a rare nerve tumor characterized by melanin-producing neoplastic Schwann cells. Wide surgical resection is the management of choice for this tumor; however, anatomical location and proximity to nerve roots can make locating this tumor and the surgical resection challenging. Here we describe the case of 49-year-old male with a melanocytic schwannoma in the presacral area adjacent to the second sacral nerve root that was managed by wide resection aided by computer-assisted navigation due to the difficulty in identifying its location intraoperatively. The utilization of computer-assisted navigation improves accuracy and precision through the creation of a virtual continuous tridimensional map, particularly useful when oftentimes tumor margins may seem equivocal and further resection would compromise the patient's functionality. The value of computer-assisted navigation for soft tissue tumor resections in orthopedic oncology is still in its infancy, though, in certain scenarios it may advance the technique for some soft tissue resections.

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, a Deceptive Misnomer for a Tumor With Relative Aggressive Behavior: A Series of 7 Cranial and Spinal Cases

The authors present in this article a series of 7 intracranial/spinal cases of melanotic schwannomas that highlight the aggressive nature of these tumors. The series comprises 2 males and 5 females, age range 19 to 50 years, with spinal/paraspinal location in 4/7 (57%), and intracranial (along the trigeminal nerve) location in 3/7 (43%). There was no association with Carney's complex. All the cases showed similar histology of epithelioid to spindled cytomorphology with vesicular nuclei (including prominent nucleoli) and conspicuous intracytoplasmic melanin pigment. Mitotic activity was seen in 3/7 cases (43%), 2 of which showed atypical forms. Immunohistochemically, all the cases were positive for S100 protein, HMB-45, melan-A and p16 protein; while negative for PDL1. Ki-67 labeling index was >5% in cases with mitotic activity. Two cases were asymptomatic (after 2.5 and 5 years postsurgery), 2 cases (one was mitotically active, while the other had no mitosis) had recurrence 6 months and 3.5 years after initial surgery, respectively, probably suggesting that mitosis alone may not be a robust predictor of biological behavior. These patients were treated with various adjuvant modalities and were alive for 4 years and 3 years of post-therapy period, respectively. Three patients were offered adjuvant radiotherapy, based on presence of aggressive histological features or significant residual tumor. One showed good clinical response. This series highlights the variability of clinical behavior of these neoplasms belying a deceptively bland nomenclature and also highlights the lack of correlation between histological features and biological behavior.

Nonepithelial Tumors and Tumor-like Lesions of the Skin and Subcutis in Children

This overview of mesenchymal tumors presenting in the skin and/or subcutis in children brings together the range of neoplasms and hamartomas which are seen in this age-group. It is not surprising from the perspective of the pediatric or general surgical pathologist that vascular anomalies, including true neoplasms and vascular malformations, are the common phenotypic category. Since there is considerable morphologic overlap among these lesions, clinicopathologic correlation may be more important than for many of the other mesenchymal tumors. The skin and subcutis are the most common sites of clinical presentation for the infantile myofibroma which is the most common of fibrous mesenchymal tumors in children. Several of the other mesenchymal tumors are more common adults-like dermatofibrosarcoma protuberans, but nonetheless have an important presence in children, even as a congenital neoplasm. A lipomatous tumor in a young child should be considered as a possible manifestation of an overgrowth syndrome.

Rexin-G®, a tumor-targeted retrovector for malignant peripheral nerve sheath tumor: A case report

Soft tissue sarcoma is a rare neoplasm of mesenchymal origin, accounting for only ~1% of all adult cancers and consisting of 75 histological subtypes. In the present report, the unique case of a 14 year-old female with metastatic malignant peripheral nerve sheath tumor (formerly, malignant melanotic schwannoma) of the parotid gland, who experienced a durable response and sustained tumor control with Rexin-G^®, a tumor-targeted retroviral expression vector encoding an anti-cyclin G1 construct, is described. Post-parotidectomy, and prior to the administration of Rexin-G^®, the patient received various chemotherapy regimens, including doxorubicin, ifosfamide, temozolomide, sorafenib, and an immunological therapy with interleukin-2, which only resulted in the further progression of lung metastases. The patient subsequently participated in a Phase 1/2 gene therapy study, during which she received intravenous Rexin-G^® as monotherapy for two years with minimal drug-associated adverse events. Currently, the patient has no evidence of active disease 9 years after commencing the Rexin-G^® treatment, and with no additional anti-cancer therapy. In conclusion, Rexin-G^® may be a viable therapeutic option for malignant peripheral nerve sheath tumors, and should be further investigated in prospective histology-specific clinical trials for this type, and possibly other types, of chemotherapy-resistant sarcoma.

A Rare Case of Aggressive Melanotic Schwannoma Occurred in Spinal Nerve of a 59-Year-Old Male

Melanotic schwannoma (MS) is a rare variant of nerve sheath neoplasm that shows ultrastructural and immunophenotypical features of Schwann cells but also has cytoplasmic melanosomes and is reactive for melanocytic markers as well. Unlike conventional schwannoma, which is totally benign, MS has an unpredictable prognosis and is thought to have low-malignant potential. Herein, we present a rare case of recurrent MS in lumbar spine of a 59-year-old male.