Metastatic malignant melanoma resembling malignant peripheral nerve sheath tumor: report of 16 cases

Undifferentiated and Dedifferentiated Metastatic Melanomas Masquerading as Soft Tissue Sarcomas: Mutational Signature Analysis and Immunotherapy Response

The distinction between undifferentiated melanoma (UM) or dedifferentiated melanoma (DM) from undifferentiated or unclassifiable sarcoma can be difficult and requires the careful correlation of clinical, pathologic, and genomic findings. In this study, we examined the utility of mutational signatures to identify patients with UM/DM with particular attention as to whether this distinction matters for treatment because the survival of patients with metastatic melanoma has dramatically improved with immunologic therapy, whereas durable responses are less frequent in sarcomas. We identified 19 cases of UM/DM that were initially reported as unclassified or undifferentiated malignant neoplasm or sarcoma and submitted for targeted next-generation sequencing analysis. These cases were confirmed as UM/DM by harboring melanoma driver mutations, UV signature, and high tumor mutation burden. One case of DM showed melanoma in situ. Meanwhile, 18 cases represented metastatic UM/DM. Eleven patients had a prior history of melanoma. Thirteen of 19 (68%) of the tumors were immunohistochemically completely negative for 4 melanocytic markers (S100, SOX10, HMB45, and MELAN-A). All cases harbored a dominant UV signature. Frequent driver mutations involved BRAF (26%), NRAS (32%), and NF1 (42%). In contrast, the control cohort of undifferentiated pleomorphic sarcomas (UPS) of deep soft tissue exhibited a dominant aging signature in 46.6% (7/15) without evidence of UV signature. The median tumor mutation burden for DM/UM vs UPS was 31.5 vs 7.0 mutations/Mb (P < .001). A favorable response to immune checkpoint inhibitor therapy was observed in 66.6% (12/18) of patients with UM/DM. Eight patients exhibited a complete response and were alive with no evidence of disease at the last follow-up (median 45.5 months). Our findings support the usefulness of the UV signature in discriminating DM/UM vs UPS. Furthermore, we present evidence suggesting that patients with DM/UM and UV signatures can benefit from immune checkpoint inhibitor therapy.

A Case of Dedifferentiated Melanoma With Lymph Node Metastasis Where Molecular Biological Tests Were Useful for Diagnosis

Malignant melanoma is known to have an altered phenotype and loss of differentiation markers for melanoma due to metastasis. Here, we report a case in which the expression of the immunohistochemical markers for melanoma was changed due to lymph node metastasis of primary cutaneous malignant melanoma. The patient, a male in his 60s, was diagnosed with malignant melanoma after undergoing excision of a skin mass. The additional excision specimen showed a small number of tumor cell clusters infiltrating the dermis. The biopsied lymph node showed completely different histological findings from those of the skin lesion and consisted of spindle-shaped tumor cells. An immunohistochemical study revealed no significant positive reactions in the lymph node tissue indicative of melanoma. The additional genetic study revealed BRAF V600e mutations in both the primary tumor and a lymph node. Together with the histological findings, the diagnosis was of metastasis of dedifferentiated melanoma to a lymph node. In summary, there is a risk of underestimation or misdiagnosis of melanoma as undifferentiated sarcoma or other tumors when melanoma metastasizes to lymph nodes and findings show a dedifferentiated or undifferentiated tumor. Therefore, as in this case, it is necessary to add a genetic study in order to make a comprehensive judgment.

Epithelioid Sarcoma of the Peripheral Nerve: Clinicopathologic Series of Three Cases and Literature Review

OBJECTIVES

Epithelioid sarcoma (ES) rarely arises in the nerve. To increase our understanding of this unusual tumor originating in the nerve, we describe the features of three cases and review the literature.

METHODS

Clinical data, imaging, pathology, treatment, and follow-up are detailed. A systematic literature review was conducted.

RESULTS

Two patients were male and one female; the median age was 24 years. The patients had neurologic symptoms, and the tumors arose in large nerves and ranged from 2.4 to 5.8 cm. The tumors were avid on positron emission tomography-computed tomography and showed increased signal intensity on T2-weighted magnetic resonance imaging. Centered in the nerve, the tumors grew with an infiltrative pattern and encased the nerve fascicles. All were treated with wide resection, and adjuvant treatment included combinations of chemotherapy and radiation. One recurred, and the limb was amputated. Metastases were documented to lymph nodes, lung, pleura, and skin. One patient died of disease after 54 months. Literature review including our cases showed that tumors stained with pancytokeratin (9/9), EMA (4/4), and CD34 (7/7); there was loss of INI1 in all six cases tested.

CONCLUSIONS

ES rarely arises in the peripheral nerve, and its infiltrative nature often requires morbid surgery. The differential includes a variety of benign and malignant epithelioid neoplasms.

Genomic Landscape of Malignant Peripheral Nerve Sheath Tumor‒Like Melanoma

Malignant peripheral nerve sheath tumor (MPNST)-like melanoma is a rare malignancy with overlapping characteristics of both neural sarcoma and melanoma. Although the genomics of cutaneous melanoma has been extensively studied, those of MPNST-like melanoma have not. To characterize the genomic landscape of MPNST-like melanoma, we performed a single-center, retrospective cohort study at a tertiary academic cancer center. Consecutive patients with a confirmed histologic diagnosis of MPNST-like melanoma were screened, and those whose tissues were locally available were included in this analysis. Archival tissue from six patients (eight samples) was submitted for whole-exome and transcriptome sequencing analysis. We compared these data with available genomic studies of cutaneous melanoma and MPNST. NF1 was altered (mutated, deleted, or amplified) in 67% of patients. Genes related to cell cycle regulation were frequently altered, with frequent deletion of ZNF331, which, to the best of our knowledge, has not been previously described in cutaneous melanoma. The serine protease inhibitor SERPINB4 was deleted in 100% of the patients. We show that MPNST-like melanoma presents overlapping genomic features with cutaneous melanoma and MPNST, but it is unique by the frequency of loss of function of ZNF331 and SERPINB4.

An Algorithmic Immunohistochemical Approach to Define Tumor Type and Assign Site of Origin

Immunohistochemistry represents an indispensable complement to an epidemiology and morphology-driven approach to tumor diagnosis and site of origin assignment. This review reflects the state of my current practice, based on 15-years' experience in Pathology and a deep-dive into the literature, always striving to be better equipped to answer the age old questions, "What is it, and where is it from?" The tables and figures in this manuscript are the ones I "pull up on the computer" when I am teaching at the microscope and turn to myself when I am (frequently) stuck. This field is so exciting because I firmly believe that, through the application of next-generation immunohistochemistry, we can provide better answers than ever before. Specific topics covered in this review include (1) broad tumor classification and associated screening markers; (2) the role of cancer epidemiology in determining pretest probability; (3) broad-spectrum epithelial markers; (4) noncanonical expression of broad tumor class screening markers; (5) a morphologic pattern-based approach to poorly to undifferentiated malignant neoplasms; (6) a morphologic and immunohistochemical approach to define 4 main carcinoma types; (7) CK7/CK20 coordinate expression; (8) added value of semiquantitative immunohistochemical stain assessment; algorithmic immunohistochemical approaches to (9) "garden variety" adenocarcinomas presenting in the liver, (10) large polygonal cell adenocarcinomas, (11) the distinction of primary surface ovarian epithelial tumors with mucinous features from metastasis, (12) tumors presenting at alternative anatomic sites, (13) squamous cell carcinoma versus urothelial carcinoma, and neuroendocrine neoplasms, including (14) the distinction of pheochromocytoma/paraganglioma from well-differentiated neuroendocrine tumor, site of origin assignment in (15) well-differentiated neuroendocrine tumor and (16) poorly differentiated neuroendocrine carcinoma, and (17) the distinction of well-differentiated neuroendocrine tumor G3 from poorly differentiated neuroendocrine carcinoma; it concludes with (18) a discussion of diagnostic considerations in the broad-spectrum keratin/CD45/S-100-"triple-negative" neoplasm.

Peritheliomatous pattern: A diagnostic clue for diagnosing metastatic melanoma in cytology

BACKGROUND

A peritheliomatous pattern (PP) in tumors is characterized by a sheath of viable tumor cells closely surrounding a central blood vessel. In the authors' cytology practice, such a PP has been recognized in several metastatic melanoma specimens. The aim of this study was to evaluate the frequency of a PP in cytology samples of melanoma in comparison with other tumors.

METHODS

Eighty archival fine-needle aspiration (FNA) cases of metastatic melanoma were compared with 65 control cases (35 poorly differentiated/metastatic carcinomas, 15 lymphomas, and 15 recurrent/metastatic/high-grade sarcomas). Cytologic findings were correlated with corresponding histologic specimens, which were available for 44 cases (55%) in the melanoma group and for 23 cases (35.38%) in the control group. All slides were examined for a PP and were semiquantitatively graded for comparison.

RESULTS

A PP was present in 51.3% of the cytologic preparations (n = 41) among the melanoma group cases, whereas in the control group, a PP was present in only 3.1% of the cases (n = 2). A PP was present in 65.9% of melanomas with available histologic sections (n = 29) and in 8.7% of tissue samples from the control group (n = 2). A PP was seen more often in cell blocks than direct smear preparations (51.3% vs 40.0%) from patients with melanoma.

CONCLUSIONS

The presence of a characteristic PP can be helpful in diagnosing melanoma in FNA samples because it was present in almost half of the metastatic melanoma cases in this study and was rarely present in other tumor types. A PP is easier to recognize and more often presents in cell blocks than aspirate smears. Ancillary studies such as immunohistochemistry are helpful for excluding other entities that may exhibit a PP.

From neural crest cells to melanocytes: cellular plasticity during development and beyond

Here, we review melanocyte development and how the embryonic melanoblast, although specified to become a melanocyte, is prone to cellular plasticity and is not fully committed to the melanocyte lineage. Even fully differentiated and pigment-producing melanocytes do not always have a stable phenotype. The gradual lineage restriction of neural crest cells toward the melanocyte lineage is determined by both cell-intrinsic and extracellular signals in which differentiation and pathfinding ability reciprocally influence each other. These signals are leveraged by subtle differences in timing and axial positioning. The most extensively studied migration route is the dorsolateral path between the dermomyotome and the prospective epidermis, restricted to melanoblasts. In addition, the embryonic origin of the skin dermis through which neural crest derivatives migrate may also affect the segregation between melanogenic and neurogenic cells in embryos. It is widely accepted that, irrespective of the model organism studied, the immediate precursor of both melanoblast and neurogenic populations is a glial-melanogenic bipotent progenitor. Upon exposure to different conditions, melanoblasts may differentiate into other neural crest-derived lineages such as neuronal cells and vice versa. Key factors that regulate melanoblast migration and patterning will regulate melanocyte homeostasis during different stages of hair cycling in postnatal hair follicles.

Immune checkpoint inhibitor therapy in a liver transplant recipient with a rare subtype of melanoma: a case report and literature review

Immunotherapy with immune checkpoint inhibitors (ICIs) may be considered as a treatment option for various types of tumors, but the transplant recipient population as well as patients requiring long-term systemic immunosuppression for other reasons have been systematically excluded from clinical trials involving ICIs. We report a case of successful treatment with ICI in a liver transplant recipient diagnosed with a rare subtype of melanoma. This patient had not required any modification to her antirejection immunosuppression before or during immunotherapy, had not experienced any serious immune-related adverse event, and had a durable objective response for nearly 1.5 year now. A summary of a literature review on other case reports is included to show that ICIs can be safe and provide clinically meaningful benefit in transplant patients, although acute rejection and graft loss remain a significant risk. Given the serious complication of graft failure, a detailed discussion of risks and benefits with immunotherapy needs to be made for an informed consent. Nevertheless, transplant recipients with cancer should not be deprived of this potentially life-saving or life-prolonging treatment, and inclusion of this population in future clinical trials should be considered.

Diagnostic immunohistochemistry through Rosai-coloured glasses

Over the past three decades, Immunohistochemistry has materially changed the practice of diagnostic surgical pathology. Foundational observations in this field were critical to a reasoned assessment of both the risks and opportunities that immunohistochemistry afforded the surgical pathologist, and our current practice draws heavily on those early assessments. As we collectively look to and acknowledge those who recognized the value of this technique and who helped guide its development as a companion to (not a replacement for) histomorphologic evaluation, we are drawn to those whose mastery of detail and ability to draw common patterns from seemingly unrelated phenomena helped define the diagnostic power of immunohistochemistry. The focus of this review is on one individual, Dr. Juan Rosai, whose contributions transcend the simple linkage of molecular observations to morphology, recognizing novel patterns in both form and color (the latter often the lovely shades of diaminobenzidine), seemingly viewing our diagnostic world at times through an entirely different lens. By looking at Dr. Rosai's early work in this field, reviewing a selection of his seminal observations, particularly in the Immunohistochemistry of thyroid and thymic neoplasia, revisiting how his special insight is often guided by the work of the early masters of morphology, and how his mentorship of others has helped shaped academic surgical pathology practice, perhaps we can get a glimpse through that lens.

Inflammation-Induced Plasticity in Melanoma Therapy and Metastasis

Phenotype switching contributes to nongenomic heterogeneity in melanoma and other cancers. These dynamic and in part reversible phenotype changes impose diagnostic and therapeutic challenges. Understanding the reciprocal coevolution of melanoma and immune cell phenotypes during disease progression and in response to therapy is a prerequisite to improve current treatment strategies. Here we discuss how proinflammatory signals promote melanoma cell plasticity and govern interactions of melanoma and immune cells in the tumor microenvironment. We examine phenotypic plasticity and heterogeneity in different melanoma mouse models with respect to their utility for translational research and emphasize the interplay between melanoma cells and neutrophils as a critical driver of metastasis.

A Preclinical Model of Malignant Peripheral Nerve Sheath Tumor-like Melanoma Is Characterized by Infiltrating Mast Cells

Human melanomas exhibit considerable genetic, pathologic, and microenvironmental heterogeneity. Genetically engineered mice have successfully been used to model the genomic aberrations contributing to melanoma pathogenesis, but their ability to recapitulate the phenotypic variability of human disease and the complex interactions with the immune system have not been addressed. Here, we report the unexpected finding that immune cell-poor pigmented and immune cell-rich amelanotic melanomas developed simultaneously in Cdk4R24C-mutant mice upon melanocyte-specific conditional activation of oncogenic BrafV600E and a single application of the carcinogen 7,12-dimethylbenz(a)anthracene. Interestingly, amelanotic melanomas showed morphologic and molecular features of malignant peripheral nerve sheath tumors (MPNST). A bioinformatic cross-species comparison using a gene expression signature of MPNST-like mouse melanomas identified a subset of human melanomas with a similar histomorphology. Furthermore, this subset of human melanomas was found to be highly associated with a mast cell gene signature, and accordingly, mouse MPNST-like melanomas were also extensively infiltrated by mast cells and expressed mast cell chemoattractants similar to human counterparts. A transplantable mouse MPNST-like melanoma cell line recapitulated mast cell recruitment in syngeneic mice, demonstrating that this cell state can directly reconstitute the histomorphologic and microenvironmental features of primary MPNST-like melanomas. Our study emphasizes the importance of reciprocal, phenotype-dependent melanoma-immune cell interactions and highlights a critical role for mast cells in a subset of melanomas. Moreover, our BrafV600E-Cdk4R24C model represents an attractive system for the development of therapeutic approaches that can target the heterogeneous tumor microenvironment characteristic of human melanomas.

Metastasis of Malignant Melanoma to Urinary Bladder: A Case Report and Review of the Literature

Aims. Metastatic malignant melanoma of the urinary bladder is a rare clinical entity, with only twenty-three published cases to date. We present a case of this rare entity, a thorough review of the literature, and differential diagnosis of melanoma in the bladder. Methods and Results. A 55-year-old woman with a history of malignant melanoma of the right thigh, excised eight years ago, presented with back pain, fatigue, and hematuria. She underwent computed tomography (CT) scan and was found to have metastases within the liver, spleen, lungs, and urinary bladder. She underwent cystoscopy and transurethral resection of three polypoid lesions. Histologic and immunohistochemical examination revealed metastatic malignant melanoma involving bladder mucosa. Conclusions. This case illustrates the importance of including malignant melanoma in the differential diagnosis of high grade neoplasms of bladder, especially in cases where the relevant clinical history is not available.

Update on Molecular Pathology of Cutaneous Melanocytic Lesions: What is New in Diagnosis and Molecular Testing for Treatment?

In this article, we give an update on recent findings regarding molecular pathology in cutaneous melanocytic tumors. The focus lies on use of genetics in the diagnosis of distinct subtypes of spitzoid tumors that are often characterized by specific phenotypic–genotypic alterations that can frequently be recognized by adequate histological examination. Typical illustrating cases are given in order to increase recognition of these lesions in daily dermatopathology practice. New molecular findings in the pathogenesis of congenital melanocytic tumors and neurocutaneous melanosis are reviewed. In addition, use of mutation analysis in the differential diagnosis of melanoma metastasis is discussed. Finally, application of mutation analysis in targeted therapy in advanced melanoma with advantages of new techniques such as next generation sequencing is described.

Growth-associated protein 43 in differentiating peripheral nerve sheath tumors from other non-neural spindle cell neoplasms

The malignant peripheral nerve sheath tumor is a relatively uncommon type of soft tissue sarcoma arising from a peripheral nerve or extraneural soft tissues and showing nerve sheath differentiation. The diagnosis of malignant peripheral nerve sheath tumor is one of the most challenging tasks in surgical pathology because of its uncommon type (5-10% soft tissue sarcomas), morphologic resemblance to other spindle cell neoplasms and lack of sensitive and specific immunohistochemical markers. The pathologic diagnosis is more straightforward in the clinical setting of neurofibromatosis-1, but problems are mainly centered on the non-neurofibromatosis-1 malignant peripheral nerve sheath tumors. To date, S100 protein is the most widely applied marker in the case of a suspected malignant peripheral nerve sheath tumor, yet its suboptimal sensitivity and its expression in other spindle cell neoplasms, including spindle cell melanoma, clear-cell sarcoma, leiomyosarcoma and monophasic synovial sarcoma, add to the diagnostic conundrum. Growth-associated protein 43 (GAP43), a membrane-associated phosphoprotein expressed in neuronal growth cones and Schwann cell precursors during neural development and axonal regeneration, was applied to a set of nerve sheath and non-nerve sheath spindle cell neoplasms. The findings in this study indicate that GAP43 is expressed in malignant peripheral nerve sheath tumors (n=18/21; 86%) and demonstrates a sensitivity superior to S100 protein (n=13/21; 62%). GAP43 is also positive in neurofibromas (n=17/18; 94%), schwannomas (n=11/12; 92%) and desmoplastic melanomas (n=7/10; 70%). In contrast, it is negative in the non-desmoplastic spindle cell melanomas (n=20/22; 91%). Of the other non-neural soft tissue sarcomas, GAP43 is non-reactive in most leiomyosarcomas (n=14/16; 88%) and clear-cell sarcomas (n=8/8), and only focally positive in monophasic synovial sarcomas (n=3/7; 43%). GAP43 is seemingly a highly sensitive marker for peripheral nerve sheath tumors and may serve as a useful diagnostic adjunct in the diagnosis of malignant peripheral nerve sheath tumor from other spindle cell neoplasms, including spindle cell melanoma.

Neurogenic tumors of soft tissue

Neurogenic tumors are an uncommon yet important category of soft tissue tumors in children and adolescents because of their frequent association with various genetic syndromes. The heterogeneous cellular composition of the peripheral nerve and the wide metaplastic capacity of the neural crest and its derivatives generate a variety of neoplasms with neurogenic differentiation. This article reviews the clinicopathologic features and differential diagnosis of neurogenic tumors in the first two decades of life, and highlights use of selected ancillary methods for diagnosis.

A literature overview of primary cervical malignant melanoma: an exceedingly rare cancer

Primary malignant melanoma (MM) of the uterine cervix is an extremely rare neoplasm, with about 78 cases described in the literature. Since traces of melanocytes in normal cervical epithelium were found in 3.5% of cases primary origin of melanoma at this site cannot be ruled out. It occurs mainly in the sixth decade of life, and it is five time less common than primary vaginal or vulvar MM. Clinical history usually includes abnormal genital bleeding; and physical examination frequently reveals a pigmented, exophytic cervical mass. Diagnosis is confirmed by immuno-histochemical methods and by exclusion of any other primary site of melanoma. Treatment of this condition is not yet standardized, and the overall prognosis is very poor. Diagnostic approaches and therapeutic procedures on primary MM of the uterine cervix are discussed following a review of the literature encompassing more than one century.

Oncogenic Braf induces melanocyte senescence and melanoma in mice

We show here that inducible expression of Braf(V600E) off the endogenous Braf gene in mouse melanocytes stimulates skin hyperpigmentation and the appearance of nevi harboring senescent melanocytes. Additionally, approximately 70% of Braf(V600E) mice develop melanomas that reproduce many of the cardinal histological and molecular features of human melanoma and whose cells can colonize the lungs of nude mice. We show that the tumor suppressor p16(INK4a) is not required to induce melanocyte senescence and that its loss is not required for tumor progression, although it does regulate tumor penetrance and latency. Thus, we have developed a mouse model of melanoma driven by Braf(V600E) expressed at physiological levels that reflects the genetics and pathology of the human disease.

Malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are a rare variety of soft tissue sarcoma of ectomesenchymal origin. MPNSTs arise from major or minor peripheral nerve branches or sheaths of peripheral nerve fibers and are derived from Schwann cells or pluripotent cells of neural crest origin. Arthur Purdy Stout played a pivotal role in the development of our current understanding of the pathogenesis of peripheral nerve sheath tumors by identifying the Schwann cell as the major contributor to the formation of benign and malignant neoplasms of the nerve sheath. Although this fact remains essentially true, the cell of origin of the MPNST remains elusive and has not yet conclusively been identified. Some have suggested these tumors may have multiple cell line origins. In the present review, MPNSTs and their epidemiology, diagnosis, management, and treatment are discussed.

Fine-needle aspiration biopsy of metastatic malignant melanoma resembling a malignant peripheral nerve sheath tumor

We report a case of metastatic malignant melanoma resembling a malignant peripheral sheath tumor, which posed a significant diagnostic challenge. The patient is a 76-year-old male, who presented in the emergency room with bilateral chest pain exacerbated by inspiration. The pain was present for 3 week and was not exacerbated by physical exercise. The diagnostic workup revealed bilateral parenchymal pulmonary infiltrates. The CT-scan guided fine-needle aspiration and the core biopsies of the largest pulmonary lesion revealed high-grade spindle cell neoplasm with individual cell apoptosis and necrosis. The immunohistochemical profile on the cell block showed that the cells are positive for Vimentin. The S-100 stain showed only focal positivity. The immunohistochemical stains for HMB45, Melan A, pancytokeratin, and smooth muscle actin were negative. Five years ago the patient was diagnosed with melanoma on the back with Clark level of IV. The melanoma was excised with clear margins and sentinel lymph nodes were negative. Careful examination of patient's previous slides revealed an area of spindle cell melanoma adjacent to a nodular type melanoma. Based on the patient's previous history, current clinico-pathologic presentation and immunohistochemical profile, the diagnosis of metastatic malignant melanoma resembling peripheral nerve sheath tumor was favored over the diagnosis of metastatic malignant spindle cell neoplasm of unknown primary site, which by itself is very rare clinical scenario.

Diagnosis and management of intracranial malignant peripheral nerve sheath tumors

OBJECTIVE

Intracranial malignant peripheral nerve sheath tumors (MPNSTs) are rare and generally carry a poor prognosis. We have analyzed our experience with MPNSTs and conducted a review of the literature in an attempt to identify a rational approach to the management of these tumors.

METHODS

Eight patients underwent surgical treatment for intracranial MPNSTs during a 10-year period from 1996 to 2005. The general strategy was to perform complete resection whenever possible and to provide adjuvant radiotherapy for residual tumor. Chemotherapy was not used in this group. The clinical, radiological, operative, and pathological findings of the patients were reviewed retrospectively.

RESULTS

Six of the eight patients underwent primary operations; two of the eight patients had previously undergone other transcranial surgery operations. Total tumor resection was achieved in five patients. At this time, two have been recurrence-free for 3.5 and 5 years, respectively, and the other three patients had a mean postoperative survival of 7 months. There was one case of near total (>90%) and two cases of partial (<90%) tumor removal; the postoperative survival rate was 4, 4, and 2 months, respectively. Only two patients in our group accepted radiotherapy after surgery; one survived only 4 months and the other has been recurrence-free for 5 years.

CONCLUSION

MPNSTs are fast-growing, invasive tumors with rather unsatisfactory outcomes. Total surgical resection seems to be the most effective therapeutic method, and radiotherapy may play a role in local control.

Differential expression of S100 protein subtypes in malignant melanoma, and benign and malignant peripheral nerve sheath tumors

BACKGROUND

Desmoplastic melanoma (DM) may simulate various benign and malignant lesions, including benign peripheral nerve sheath tumors (BPNSTs) and malignant peripheral nerve sheath tumors (MPNSTs). The latter case is diagnostically challenging because DM generally show only S100 protein expression but no reaction to melanocytic markers. S100 family of proteins consists of over 20 members. We report on S100 subtypes in malignant melanomas (MMs), and BPNSTs and MPNSTs to investigate differential expression.

DESIGN

S100A1, S100A2, S100A4, S100A6 and S100B immunostains were performed on 80 MMs including conventional and desmoplastic types, 86 BPNSTs and 77 MPNSTs.

RESULTS

S100A1 expression was seen in > 91% of MMs in a diffuse reaction, whereas BPNSTs showed focal or no reaction. Sixteen percent of MPNSTs focally expressed S100A1 except for one case with diffuse reaction. S100A2 staining was negative or focal in all three groups whereas S100A4 reaction was variable in all three. S100A6 was diffusely expressed in MMs, BPNSTs and MPNSTs. S100B was stained diffusely in MMs and BPNSTs, but its reaction was observed in 30% of MPNSTs in a focal fashion.

CONCLUSION

S100A1 expression was diffuse in most of MMs but absent or focal in BPNSTs and MPNSTs. This may be helpful to distinguish between the two entities.

MALIGNANT PERIPHERAL NERVE SHEATH TUMOR OF THE OCCIPITAL REGION

OBJECTIVE

A rare case of a malignant peripheral nerve sheath tumor of the occipital region is presented. The role of postoperative radiotherapy in such cases is reviewed.

CLINICAL PRESENTATION

A 36-year-old man presented with a small spongy swelling in the posterior aspect of the cranium since childhood. The swelling gradually increased for 2 years and then rapidly over the next 7 months. There were no associated symptoms of headache, vomiting, vertigo, focal weakness, or visual impairment.

INTERVENTION

A small occipital craniectomy for total excision of the tumor was attempted. However, as a result of intracranial extension to the transverse sinus, the tumor could not be completely excised. Local radiotherapy to a dose of 59.4 Gy in 33 fractions over 6.5 weeks was delivered to the residual microscopic disease in the posterior part of the cranium. The patient has been followed up regularly for the past 28 months and continues to remain asymptomatic.

CONCLUSION

An aggressive malignant peripheral nerve sheath tumor of an atypical site such as the scalp, in which complete surgery may not always be possible, could benefit from postoperative radiotherapy. A dose of approximately 60 Gy could be effectively delivered with a satisfactory outcome.

Divergent differentiation in malignant melanomas: a review

The aim of this review was to document and discuss diagnostic problems associated with divergent differentiation ('metaplastic change') in malignant melanomas, defined as the development in these tumours of morphologically, immunohistochemically and/or ultrastructurally recognizable non-melanocytic cell or tissue components. Types of divergent differentiation reported in malignant melanoma include: fibroblastic/myofibroblastic, Schwannian and perineurial, smooth muscle, rhabdomyosarcomatous, osteocartilaginous, ganglionic and ganglioneuroblastic, neuroendocrine and probable epithelial. Divergent differentiation is certainly a rare phenomenon and, when it occurs, can be missed by unwary pathologists and lead to diagnostic uncertainty. A carefully chosen immunohistochemical panel and the input of electron microscopy can help to clarify the nature of the cellular differentiation of these tumours and lead to a correct final diagnosis. The clinical significance of such aberrations is uncertain, nor are the underlying mechanisms as yet well defined.

A novel mutation in the XPA gene associated with unusually mild clinical features in a patient who developed a spindle cell melanoma

BACKGROUND

Xeroderma pigmentosum (XP) is an autosomal recessive disorder of, in most cases, defective nucleotide excision repair (NER) of ultraviolet radiation (UV)- and chemical-induced DNA damage. The condition is characterized by an increased sensitivity of the skin to UV radiation, with early development of pigmentary changes and premalignant lesions in sun-exposed areas of the skin, signs of photoageing and a greatly increased incidence from a young age of skin tumours including melanoma. Approximately 20% of patients with XP show neurological abnormalities of varying severity due to primary neuronal degeneration. Genetic analysis by somatic cell hybridization has led to the identification in the NER-defective form of XP of seven complementation groups, designated XP-A to XP-G. These complementation groups correspond to different proteins involved in the NER process. XP-A classically includes some of the most severely affected patients.

OBJECTIVES

We describe a 61-year-old Punjabi woman with XP. Remarkably she had only mild cutaneous abnormalities, minimal neurological features and unusual longevity, and developed a malignant spindle cell melanoma. There are few previous reports of spindle cell melanoma associated with XP. To gain insight into the aetiology of these unusual features, we sought to analyse the DNA repair properties of the patient and identify the complementation group and the causative mutation in the defective gene.

METHODS

Unscheduled DNA synthesis and the inhibition of RNA synthesis were measured. The complementation group was assigned by fusing the cells of our patient with XP cells of known complementation groups and determining the ability to carry out unscheduled DNA repair. Molecular analysis of the cDNA was carried out by polymerase chain reaction and DNA sequencing.

RESULTS

Levels of DNA repair were extremely low and complementation analysis assigned the defect to the XP-A group. Sequencing of the XPA gene revealed a novel homozygous mutation of A-->G at the eighth nucleotide of intron 4 causing aberrant splicing and a nonfunctional truncated XP-A protein. However, a small amount of normally spliced mRNA was detected at <5% the level in normal cells.

CONCLUSIONS

The small amount of normally spliced mRNA detected may be sufficient to explain the relatively mild clinical features in our patient.

Primary Malignant Melanoma of the Uterine Cervix

BACKGROUND

Malignant melanoma of the uterine cervix is a rare neoplasm with poor prognosis. Diagnosis is confirmed by immunohistochemical methods and by exclusion of other primary sites of melanoma.

CASE

In this paper, we are reporting a case of a 38-year-old patient with a malignant melanoma of the uterine cervix. Diagnosis was made by histological and immunohistochemical method. The tumor was stage IB1 of the International Federation of Gynecology and Obstetrics classification. Chest x-ray and abdominopelvic computed tomography scanning were normal. A radical hysterectomy with bilateral salpingo-oophorectomy and pelvic lymphadenectomy was performed. After performing combined radical surgery and irradiation, complete remission of the tumor was achieved. The patient has been followed for 24 months. She is well without any symptoms or signs of recurrence.

CONCLUSIONS

Malignant melanoma is usually misdiagnosed specially in the chronic form. The immunohistochemical study is useful for definite diagnosis. Treatment is not well established, and the disease histogenesis has been controversial for a long time.

The use of immunohistochemistry in the differential diagnosis of tumors of the testis and paratestis

Although most testicular and paratesticular tumors can be recognized by their light microscopic features, some raise significant differential diagnostic questions. Immunohistochemical staining has proved of significant value in this situation. There is still a role for the traditional markers, including placental-like alkaline phosphatase and alpha-fetoprotein, but newer markers provide additional support and often have greater sensitivity and specificity for many diagnoses. OCT4 is virtually 100% sensitive and specific for seminoma, embryonal carcinoma, and intratubular germ cell neoplasia, unclassified type. Inhibin-alpha, among testicular tumors, is limited to those in the sex cord-stromal category or those having adrenocortical-type differentiation (testicular tumor of the adrenogenital syndrome) or of trophoblastic lineage. Calretinin is another positive marker for the sex cord-stromal tumors but has less specificity. Additional markers, including differential cytokeratins, c-kit, CD30, epithelial membrane antigen, S-100, melan-A, and others, are useful in specific situations. This article reviews the application of immunohistochemical markers for a number of differential diagnostic considerations in the testis and paratestis categorized according to their light microscopic patterns.

Unusual histological variants of cutaneous malignant melanoma with some clinical and possible prognostic correlations

Malignant melanoma is known for the wide range of histological patterns it can assume mimicking other malignant tumors. We present a review of most of the unusual histological variants of cutaneous melanoma and describe their immunohistochemical features, associate clinical findings, and possible behavior related to the histological subtype. In addition, we propose their classification into four groups corresponding to the (1) architectural patterns; (2) cytologic features; (3) stromal changes; and (4) the possible association of these findings (i.e. architectural + cytologic features). Although most of these unusual variants have the same prognosis as conventional melanomas, with Breslow thickness and ulceration, being the most important predictor of survival in clinical stage I, some of them have a peculiar biologic behavior that the clinicians and the dermatopathologists should know in order to give melanoma patients all educational information available.

Acute monocular blindness resulting from transformation of von Recklinghausen's neurofibromatosis to malignant melanocytic schwannomas

A 59-year-old male was transferred to our facility after initial workup for left eye blindness revealed multiple brain lesions. The patient presented with scant pedunculated skin lesions on his neck and arms, axillary freckling and bilateral subcutaneous ankle nodules suggestive of neurofibromatosis type 1 (NF-1). Neurological examination revealed left-sided blindness, diminished pupillary response to light, incomplete eyelid closure and facial droop. A CT series of the chest/abdomen/pelvis demonstrated several lesions in the lungs, liver and left kidney. CT-guided biopsy of the renal lesion was "consistent with metastatic melanoma" based on the presence of malignant cell staining for the melanocyte differentiation antigen MART-1, as well as the calcium binding protein S-100. A dermatology consultant confirmed neurofibromas and a café au lait macule. No dysplastic nevi or primary melanoma were identified. An ophthalmology consultant noted gray choroidal lesions on fundoscopic examination thought to be metastatic disease of unknown primary. Despite treatment with whole brain irradiation and intravenous steroids, the patient died on hospital day 10. A full autopsy showed diffuse neurofibromas and café au lait macules consistent with NF-1 and malignant melanocytic schwannomas with multiple metastases.

Epithelioid malignant peripheral nerve sheath tumor. Report of a case with inflammatory infiltration

The epithelioid malignant peripheral nerve sheath tumor (EMPNST) is a rare sarcoma originating from the supportive non-neuronal components of peripheral nerves. Our patient was a 75-year-old Japanese man who presented with complaints about pain and a mass in the left thigh. Characteristic histopathological features were large epithelioid-like cells closely resembling a malignant melanoma or another type of soft tissue tumor. Notable infiltration of neutrophils in the tumor was seen. Immunohistochemically, the tumor cells proved positive for S-100, NSE, GFAP, MBP, chromogranin A and synaptophysin, and negative for CEA, keratin, HMB-45, G-CSF, and GM-CSF. Tumor-related inflammatory infiltration may be caused by an autonomous production of some cytokines. However, these tumor cells were negative for G-CSF and GM-CSF so that the mechanism triggering inflammatory infiltration is unclear. Electron microscopy revealed the presence of an extracellular basal lamina, intermediate cell junctions, and numerous dense-cored granules in the cytoplasm. These findings suggested a schwannian derivation, consistent with the diagnosis of EMPNST. There have been reports on S-100 positivity and HMB-45 negativity of this tumor type, but to the best of our knowledge, this is the first description of an EMPNST positive for MBP, chromogranin A, and synaptophisin. Where unequivocal features are lacking, these markers might be useful for differential diagnosis.

Distinction of desmoplastic melanoma from non-desmoplastic melanoma by gene expression profiling

Desmoplastic melanoma (DM) is a variant of melanoma characterized by the presence of amelanotic fusiform melanocytes dispersed in a prominent collagenous stroma. DM behaves differently from conventional non-desmoplastic melanoma (NDM). It has a higher tendency for local recurrence and is less likely to metastasize to regional lymph nodes. In this study, we explored the possibility of distinguishing DM from NDM by gene expression profiling. RNA samples from ten primary cutaneous melanomas of similar depth of invasion were analyzed using the Affymetrix U133A oligonucleotide platform. Four tumors were DM, five were ND, and one tumor showed combined features of desmoplastic and conventional. Hierarchical cluster analysis clearly separated DM from NDM. The expression of a number of melanocyte differentiation genes was decreased in DM compared with NDM, which corresponded to immunohistochemical results. Various genes were upregulated in DM, including neurotrophic factors and genes involved in extracellular matrix production. A novel finding was the high expression of clusterin in DM, which was confirmed by immunohistochemical studies. Our results from gene expression profiling validate the distinction of DM from NDM. They also provide the opportunity to learn more about the biology of DM which had previously not yet been associated with this variant of melanoma.

Niedrig-maligne periphere Nervenscheidentumoren der Nasen- und Nasennebenh�hlenschleimhaut

Sinonasal malignant peripheral nerve sheath tumors (MPNST) are infrequent neoplasms. 16 cases of low-malignant MPNST in this localization were retrieved from the files of soft tissue tumors established in Jena. They were examined with regard to their morphology and immunohistochemistry. The importance of an only partial immunostaining by S100 protein antibodies for diagnosis and differential diagnostic discrimination to benign peripheral nerve sheath tumors (schwannomas and neurofibromas) is explained. Finally, the differential diagnosis of spindle cell tumors in the sinonasal region in general is briefly discussed.

Non-melanocytic lesions mimicking melanocytic lesions

Distinction between benign and malignant melanocytic lesions commonly represents a big challenge for the pathologist. Equally difficult is separating tumours with melanocytic lineage from those displaying other lines of differentiation. This is because benign and malignant melanocytic lesions are able to display a wide range of histological appearances that frequently closely mimic reactive and neoplastic lesions (benign and malignant). This applies to processes with almost any line of differentiation. Difficulties in differential diagnosis are mainly found in melanocytic lesions restricted to the dermis or those in which the junctional component is minimal. Although purely junctional melanocytic lesions less commonly pose a problem in differential diagnosis, they may be very problematic, especially in small biopsies. Immunohistochemistry is usually a very important aid in the differential diagnosis of mimics of melanocytic lesions but pitfalls often occur. This is particularly true when small samples are analysed and when close clinicopathological correlation is lacking. This review discusses the histological differential diagnosis of mimics of melanocytic lesions. These mimics are separated into those primarily presenting in the epidermis and those presenting in the dermis.

Utility of image guided surgery in the diagnosis of pterygopalatine fossa lesions

OBJECTIVES

To describe the utility of image guided surgery in the diagnosis of pterygopalatine fossa lesions and to discuss the varied pathologic diagnoses from this area.

STUDY DESIGN

Case series presentation.

METHODS

Three cases of pterygopalatine fossa lesions were accessed and biopsied by way of a middle meatus antrostomy approach into the pterygopalatine fossa under image guidance for rapid localization.

RESULTS

The diagnoses of melanoma, squamous cell carcinoma, and schwannoma were obtained with minimal morbidity with image guidance. More extensive external approaches were avoided, and appropriate treatment was started without delay. The utility of the image guided approach will be discussed along with the varied pathologies encountered in the pterygopalatine fossa.

CONCLUSIONS

1). One must recognize the diverse, yet related, symptoms of patients presenting with pterygopalatine fossa lesions. Early recognition as well as skull-base imaging is crucial. 2). Biopsy, in addition to imaging, is necessary for diagnosis and may be achieved with little morbidity and increased accuracy using the image guided surgery middle meatus antrostomy approach to the pterygopalatine fossa. 3). The origin of lesions that involve the pterygopalatine fossa may be difficult to identify. Involvement of the pterygopalatine fossa by malignancy may be by contiguous spread, by way of metastasis, or by perineural invasion.

Differential diagnosis of non-epithelial tumors of the pancreas: malignant non-epithelial pancreatic tumor with focal pigmentation

Non-epithelial tumors only rarely affect the pancreas. In this report, we describe a malignant non-epithelial tumor with combined characteristics of malignant peripheral nerve sheath tumor (MPNST) and malignant melanoma. To more closely define the differential diagnosis of MPNST with focal pigmentation versus metastatic melanoma resembling MPNST, the tumor was investigated using histomorphology, immunohistochemistry, electron microscopy, and comparative genomic hybridization. As a result, from these analyses and from clinical findings, the diagnosis of a pancreatic MPNST with focal pigmentation was favored. However, the diagnosis of a malignant melanoma or a composite tumor could not be definitely ruled out, due to the considerable morphological and genotypical overlap between both entities, which can be explained by the close histogenetic relationship between both tumor entities.

Malignant peripheral nerve sheath tumour-like primary cutaneous malignant melanoma

Malignant melanoma is known for its protean cytomorphological features, architectural patterns, and stromal changes, in addition to its ability to mimic various benign and malignant non-melanocytic tumours. Anecdotal cases of metastatic malignant melanoma simulating soft tissue sarcomas have been reported. Interestingly, this mimicry is more often seen in recurrent lesions and metastatic deposits. This report describes a case of a primary spindle cell cutaneous malignant melanoma with a prominent neural-like fascicular pattern and nuclear palisading, simulating a conventional malignant peripheral nerve sheath tumour (MPNST). Clinical, microscopic, and immunohistochemical features of the different entities included in the differential diagnosis of cutaneous spindle cell malignant tumours, such as MPNST, atypical fibroxanthoma, and spindle cell squamous cell carcinoma are discussed. Of note, the presence of an atypical epidermal or junctional component, cell pigmentation, and cell nesting, in addition to diffuse and strong reactivity for S-100 protein and other melanocytic markers, are helpful in the diagnosis of these troublesome lesions.

Ganglioneuroblastic differentiation in a primary cutaneous malignant melanoma

Ganglioneuroblastic differentiation in malignant melanomas is an exceedingly rare event. Although there has been a single report of this occurrence in a metastatic melanoma, divergent ganglioneuroblastic differentiation has not been documented previously in a primary cutaneous lesion of melanoma. The present report describes an unusual case of invasive melanoma arising on the lower leg of a 61-year-old woman. The 16.9-mm thick tumor showed extensive ganglioneuroblastic differentiation, which was confirmed both immunohistochemically and ultrastructurally. Although the prognostic significance of this observation remains uncertain, the unique case reaffirms the potential morphologic diversity of melanomas and suggests a shared histogenetic origin from a common neural crest derivative.

Expression of protein gene product 9.5 in epithelioid and conventional malignant peripheral nerve sheath tumors

CONTEXT

Due to the frequent lack of S100 protein expression in malignant peripheral nerve sheath tumors (MPNSTs), especially the epithelioid variant, these tumors are difficult to diagnose without the aid of electron microscopy or a clinical history of neurofibromatosis.

METHODS

Protein gene product 9.5 (PGP9.5), a broad neural marker, is expressed in nerve fibers and neurons of both the peripheral and central nervous systems. We compared its expression to that of S100 protein in 16 cases of MPNST. As controls, 6 monophasic synovial sarcomas, 9 leiomyosarcomas, and 5 dermatofibrosarcoma protuberans were included.

RESULTS

Expression of PGP9.5 was seen in 15 MPNSTs, with 3 to 4+ positivity in the majority of the cases. Ten cases, 2 epithelioid and 8 conventional MPNSTs, were reactive with PGP9.5, but were negative for S100 protein. Five cases were immunoreactive for both S100 protein and PGP9.5. One case was negative for PGP9.5 but demonstrated focal S100 protein positivity. Expression of PGP9.5 was seen in 4 of 6 synovial sarcomas, 3 of 9 leiomyosarcomas, and none of 5 dermatofibrosarcoma protuberans.

CONCLUSION

Although PGP9.5 is not a specific marker for MPNST, it is a more sensitive marker than S100 protein (94% vs 38%). When there is a lack of S100 protein expression and a broad panel of immunostains, such as cytokeratin, epithelial membrane antigen, and smooth muscle actin, yields only focal or equivocal staining, PGP9.5 is a useful diagnostic adjunct in confirming the neural origin of a spindle cell sarcoma.

Primary extrapulmonary sugar tumor (PEST): a report of four cases

The cell of origin and direction of differentiation of the clear cell tumor of the lung (the so-called sugar tumor) remains enigmatic. Recognition of HMB-45 immunoreactivity and identification of melanosomes have suggested a relationship to angiomyolipoma of kidney or liver and lymphangiomyoma. This has given rise to the concept that clear cell tumors are neoplasms of so-called perivascular epithelioid cells--PEComas. Herein we report the existence of four similar tumors occurring in extrapulmonary sites, one of which had malignant features. The three benign tumors occurred in females ages 9, 20, and 40 years; two were located in the rectum and one in the vulva. The malignant tumor occurred in the inter-atrial cardiac septum of a 29-year-old man. Common histologic features were a richly vascular organoid architecture, tumor cells with clear to pale eosinophilic cytoplasm, abundant glycogen, and immunoreactivity for HMB 45, but not S100, multiple keratin, neuroendocrine, or muscle markers. Benign tumors demonstrated low mitotic activity, no necrosis, and good circumscription; the malignant tumor showed considerable mitotic activity, necrosis, and an infiltrative growth pattern. Ultrastructurally, glycogen was present, mitochondria were abundant, and membrane-bound lamellated bodies consistent with premelanosomes were present in two cases, and equivocal in one. Because these tumors have light microscopic, immunohistochemical, and electron microscopic features similar to pulmonary sugar tumors, we propose the name primary extrapulmonary sugar tumor (PEST) for them. Although most PEST's are probably benign, malignant forms appear to exist. These cases further support the concept of a family of systemic HMB-45 positive tumors that include sugar tumors, angiomyolipoma of kidney or liver, lymphangiomyomas, and clear-cell myomelanocytic tumors of the falciform ligament/ligamentum teres.

Clear cell variant of malignant melanoma of the uterine cervix: a case report and review of the literature

BACKGROUND

A rare variant of malignant melanoma of the uterine cervix mimicking clear cell carcinoma or clear cell sarcoma is described.

CASE

A 33-year-old Japanese woman was admitted to the hospital complaining of genital discharge and lower back pain. The stage was FIGO IIB and radical hysterectomy and pelvic lymphadenectomy were done. Pathological examination, immunohistochemical studies of melanin granules, and molecular analysis of the EWS/ATF-1 fusion gene were also done. A diffuse proliferation of amelanotic clear cells was detected in the uterine cervix. Tumor cells were positive for HMB 45, Melan-A (MART-1), and S-100 protein and negative for epithelial markers. The EWS/ATF-1 fusion gene was not detected.

CONCLUSION

This is apparently the first report of a case of clear cell melanoma of the uterine cervix. Despite its rarity, this variant of malignant melanoma should be considered when diagnosing clear cell neoplasms of the uterine cervix.