Diagnostic value of Sox10 immunohistochemical staining for the detection of metastatic melanoma in sentinel lymph nodes

Evaluation of SOX-10 immunohistochemical expression in canine melanoma and non-melanocytic tumors by tissue microarray

Melanoma is the most common malignant oral tumor in dogs. It frequently presents a diagnostic challenge as many melanomas lack or contain scant melanin and may have a variable microscopic phenotype. Previous studies evaluating immunohistochemical markers for diagnosing melanoma have shown limited sensitivity and/or specificity for S-100, PNL2, melan A, TRP-1, TRP-2, and HMB-45. Sry-related HMG-box gene 10 (SOX-10) is a transcription factor associated with melanocytic, peripheral neural crest, and peripheral nervous system development. In humans, SOX-10 expression has been demonstrated in melanoma, breast carcinoma, glioma, and schwannoma, but has only recently been explored in veterinary species. In this study, 198 tumors comprised of 147 melanocytic neoplasms and 51 non-melanocytic neoplasms were evaluated by immunohistochemistry using a tissue microarray for SOX-10, PNL2, melan A, TRP-1, and TRP-2 expressions. The SOX-10 had the highest diagnostic sensitivity (96.7%) in melanomas. In addition, SOX-10 had the highest percentage (91.5%; 130/142) of melanomas label at least 75% of neoplastic cells. Of the 51 selected non-melanocytic tumors examined, SOX-10 labeling was observed in mammary carcinomas (6/6), gliomas (4/4), and oral soft tissue sarcomas (4/18). Of the 41 non-melanocytic oral neoplasms evaluated, SOX-10 had a specificity of 92.7%. Therefore, SOX-10 represents a useful immunohistochemical screening marker for the diagnosis of canine melanoma given its extremely high sensitivity and robust labeling intensity. The SOX-10 may have utility in diagnosing some non-melanocytic neoplasms in the dog, although this requires further investigation.

Sentinel lymph node assessment in melanoma: current state and future directions

Assessment of sentinel lymph node status is an important step in the evaluation of patients with melanoma for both prognosis and therapeutic management. Pathologists have an important role in this evaluation. The methodologies have varied over time, from the evaluation of dimensions of metastatic burden to determination of the location of the tumour deposits within the lymph node to precise cell counting. However, no single method of sentinel lymph node tumour burden measurement can currently be used as a sole independent predictor of prognosis. The management approach to sentinel lymph node-positive patients has also evolved over time, with a more conservative approach recently recognised for selected cases. This review gives an overview of past and current status in the field with a glimpse into future directions based on prior experiences and clinical trials.

Tissue Biomarkers Predicting Lymph Node Status in Cutaneous Melanoma

Cutaneous melanoma is a severe neoplasm that shows early invasiveness of the lymph nodes draining the primary site, with increased risk of distant metastases and recurrence. The tissue biomarker identification could be a new frontier to predict the risk of early lymph node invasiveness, especially in cases considered by current guidelines to be at low risk of lymph node involvement and not requiring evaluation of the sentinel lymph node (SLN). For this reason, we present a narrative review of the literature, seeking to provide an overview of current tissue biomarkers, particularly vascular endothelium growth factors (VEGF), Tetraspanin CD9, lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1), D2-40, and gene expression profile test (31-GEP). Among these, 31-GEP seems to be able to provide a distinction between low or high risk for positive SLN classes. VEGF receptor-3 and CD9 expression may be independent predictors of positive SLN. Lastly, LYVE-1 and D2-40 allow an easier assessment of lymph vascular invasion, which can be considered a good predictor of SLN status. In conclusion, biomarkers to assess the lymph node status of cutaneous melanoma patients may play an important role in those cases where the clinician is in doubt whether or not to perform SLN biopsy.

Actualities in the Morphology and Immunohistochemistry of Cutaneous and Ocular Melanoma: What Lies Ahead? A Single-Centre Study

Melanoma is the most aggressive melanocytic tumor whose incidence is continuously increasing worldwide.

METHODS

We highlight the morphological, immunohistochemistry, and particularities of various melanoma types based on the cases diagnosed in our department from 2017 to 2021.

RESULTS

We present 100 melanoma cases and one capsular nevus case. The most common type was nodular melanoma. The immunohistochemistry markers used were SRY-box transcription factor 10 (SOX10), S100 protein, human melanoma black 45 (HMB45), and melanoma antigen recognized by T cells 1 (Melan-A). Uveal melanoma and conjunctival melanoma represent particular tumors with independent prognostic factors. Uveal melanoma requires assessment of macrophages, microvascularisation, and mitoses. Sentinel lymph node metastases are essential targets that provide staging tools. Conjunctival melanoma and capsular nevi are diagnostic pitfalls.

CONCLUSION

Melanoma can appear in various forms, and sometimes the diagnosis might be unclear. Today, immunohistochemistry remains the most important tool in confirming the diagnosis and prognosis for this type of neoplasia.

Targeting SOX10-deficient cells to reduce the dormant-invasive phenotype state in melanoma

Cellular plasticity contributes to intra-tumoral heterogeneity and phenotype switching, which enable adaptation to metastatic microenvironments and resistance to therapies. Mechanisms underlying tumor cell plasticity remain poorly understood. SOX10, a neural crest lineage transcription factor, is heterogeneously expressed in melanomas. Loss of SOX10 reduces proliferation, leads to invasive properties, including the expression of mesenchymal genes and extracellular matrix, and promotes tolerance to BRAF and/or MEK inhibitors. We identify the class of cellular inhibitor of apoptosis protein-1/2 (cIAP1/2) inhibitors as inducing cell death selectively in SOX10-deficient cells. Targeted therapy selects for SOX10 knockout cells underscoring their drug tolerant properties. Combining cIAP1/2 inhibitor with BRAF/MEK inhibitors delays the onset of acquired resistance in melanomas in vivo. These data suggest that SOX10 mediates phenotypic switching in cutaneous melanoma to produce a targeted inhibitor tolerant state that is likely a prelude to the acquisition of resistance. Furthermore, we provide a therapeutic strategy to selectively eliminate SOX10-deficient cells.

Signal pathways of melanoma and targeted therapy

Melanoma is the most lethal skin cancer that originates from the malignant transformation of melanocytes. Although melanoma has long been regarded as a cancerous malignancy with few therapeutic options, increased biological understanding and unprecedented innovations in therapies targeting mutated driver genes and immune checkpoints have substantially improved the prognosis of patients. However, the low response rate and inevitable occurrence of resistance to currently available targeted therapies have posed the obstacle in the path of melanoma management to obtain further amelioration. Therefore, it is necessary to understand the mechanisms underlying melanoma pathogenesis more comprehensively, which might lead to more substantial progress in therapeutic approaches and expand clinical options for melanoma therapy. In this review, we firstly make a brief introduction to melanoma epidemiology, clinical subtypes, risk factors, and current therapies. Then, the signal pathways orchestrating melanoma pathogenesis, including genetic mutations, key transcriptional regulators, epigenetic dysregulations, metabolic reprogramming, crucial metastasis-related signals, tumor-promoting inflammatory pathways, and pro-angiogenic factors, have been systemically reviewed and discussed. Subsequently, we outline current progresses in therapies targeting mutated driver genes and immune checkpoints, as well as the mechanisms underlying the treatment resistance. Finally, the prospects and challenges in the development of melanoma therapy, especially immunotherapy and related ongoing clinical trials, are summarized and discussed.

Biomarkers for Diagnosis, Prognosis and Response to Immunotherapy in Melanoma

Simple Summary

Cutaneous Melanoma is a form of skin cancer characterized by an elevated mutational load that favors high spread to distant organs and resistance to therapies. The identification of biomarkers, able to dissect normal and pathogenic biological processes and response to therapeutic intervention, is necessary to describe melanoma as accurately as possible, having a positive impact on early diagnosis, in turn selecting the best therapeutic option. Recently, a great number of new biomarkers were evaluated, in order to identify those patients who may have clinical benefit from a therapeutic choice, particularly for immunotherapy. At present, these new biomarkers wait to be validated before clinical use. Hence, the requirement to look at and periodically update the advances in this field.

Abstract

Cutaneous Melanoma classification is constantly looking for specific and sensitive biomarkers capable of having a positive effect on diagnosis, prognosis and risk assessment, eventually affecting clinical outcome. Classical morphological, immunohistochemical and the well-known BRAF and NRAS genetic biomarkers do not allow the correct categorization of patients, being melanoma conditioned by high genetic heterogeneity. At the same time, classic prognostic methods are unsatisfactory. Therefore, new advances in omics and high-throughput analytical techniques have enabled the identification of numerous possible biomarkers, but their potentiality needs to be validated and standardized in prospective studies. Melanoma is considered an immunogenic tumor, being the first form of cancer to take advantage of the clinical use of the immune-checkpoint blockers. However, as immunotherapy is effective only in a limited number of patients, biomarkers associated with different responses are essential to select the more promising therapeutic approach and maximize clinical benefits. In this review, we summarize the most utilized biomarkers for Cutaneous Melanoma diagnosis, focusing on new prognostic and predictive biomarkers mainly associated with immunotherapy.

Melanoma Biomarkers and Their Potential Application for In Vivo Diagnostic Imaging Modalities

Melanoma is the deadliest form of skin cancer and remains a diagnostic challenge in the dermatology clinic. Several non-invasive imaging techniques have been developed to identify melanoma. The signal source in each of these modalities is based on the alteration of physical characteristics of the tissue from healthy/benign to melanoma. However, as these characteristics are not always sufficiently specific, the current imaging techniques are not adequate for use in the clinical setting. A more robust way of melanoma diagnosis is to "stain" or selectively target the suspect tissue with a melanoma biomarker attached to a contrast enhancer of one imaging modality. Here, we categorize and review known melanoma diagnostic biomarkers with the goal of guiding skin imaging experts to design an appropriate diagnostic tool for differentiating between melanoma and benign lesions with a high specificity and sensitivity.

SOX10 is as specific as S100 protein in detecting metastases of melanoma in lymph nodes and is recommended for sentinel lymph node assessment

BACKGROUND

Sentinel lymph node (SLN) biopsy remains crucial for melanoma staging. The European Organisation for Research and Treatment of Cancer Melanoma Group recommends performing immunohistochemical stainings for reproducible identification of melanoma metastases. S100 protein (pS100) is a commonly used melanocytic antigen because of its high sensitivity in spite of relatively low specificity. SRY-related HMG-box 10 protein (SOX10) is a transcription factor characterising neural crest-derived cells. It is uniformly expressed mostly in the nuclei of melanocytes, neural, and myoepithelial cells. Pathologists sometimes prefer SOX10 as a melanoma marker, but it has not yet been investigated on a large-scale to confirm that it is reliable and recommendable for routine SLN evaluation.

METHODS

Four hundred one treatment-naïve lymph node (LN) metastatic melanomas were included in high-density tissue microarrays and were assessed for the presence of SOX10 and pS100 by immunohistochemistry. The slides were digitalised, shared and evaluated by a panel of experienced melanoma pathologists.

RESULTS

The vast majority of melanomas were double-positive for pS100 and SOX10 (93.2%); a small percentage of the cases (3.9%) were double-negative melanomas. Discordance between the two markers was observed: 1.9% pS100(-)/SOX10(+) and 0.75% pS100(+)/SOX10(-). SOX10 was not expressed by immune cell types in the LN, resulting in a less controversial interpretation of the staining.

CONCLUSIONS

SOX10 is as equally specific as pS100 for the detection of melanoma metastases in LNs. The interpretation of SOX10 staining is highly reproducible among different centres and different pathologists because of the absence of staining of immune cells.

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.

Can SOX-10 or KBA.62 Replace S100 Protein in Immunohistochemical Evaluation of Sentinel Lymph Nodes for Metastatic Melanoma?

BACKGROUND

Microscopic evaluation of sentinel lymph nodes for metastatic melanoma relies, in part, on the use of immunohistochemical analysis to identify minute metastatic deposits that may be overlooked on routine microscopy. At present S100 protein is widely used in this role, in large part for its superior sensitivity; however, interpretation is hampered by the presence of benign S100 protein-positive cellular elements present in every lymph node, leading to reduced specificity and consequent difficulties in interpretation. In recent years, multiple melanocytic markers have emerged that promise superior sensitivity and specificity, including KBA.62 and SOX-10. SOX-10 shows a nuclear pattern of staining. In normal tissue it is expressed in Schwann cells, melanocytes, and myoepithelial cells of salivary, bronchial, and mammary glands. KBA.62 is also specific except for staining of endothelial cells and shows a membranous staining pattern. This study was undertaken to determine whether KBA.62 or SOX-10 could equal (or surpass) the sensitivity of S100 protein while offering superior specificity in the immunohistochemical evaluation of sentinel lymph nodes for metastatic melanoma.

DESIGN

In this study we performed immunohistochemical stains for S100 protein, Sox-10, and KBA.62 on 50 lymph nodes with proven metastatic melanoma.

RESULTS

SOX-10 detected all cases of metastatic melanoma (50 of 50 cases; 100%) compared with S100 protein (48 of 50 cases; 96%) and KBA.62 (37 of 50 cases; 74%). There was no "background" staining of normal cellular elements with SOX-10 or KBA.62. In contrast, S100 protein was expressed in scattered dendritic interdigitating reticulum cells in the paracortex of lymph nodes, showing cytoplasmic and nuclear positivity, sometimes posing significant difficulty in differentiating benign reticulum cells from single cell metastatic melanoma.

CONCLUSIONS

Our findings suggest that SOX-10 may be superior to S100 protein for identifying metastatic melanoma in a lymph node. KBA.62 was less sensitive than either marker, although more specific than S100 protein.

Immunohistochemistry in dermatopathology

CONTEXT

Immunohistochemistry is not a diagnostic test but a highly valuable tool that requires interpretation within a context.

OBJECTIVE

To review the current status and limitations of immunohistochemistry in dermatopathology.

DATA SOURCES

English-language literature published between 1980 and 2014.

CONCLUSIONS

Although immunohistochemistry is rarely completely specific or sensitive, it is an important adjunctive technique in dermatopathology and can be helpful in a series of diagnostic dilemmas.

Challenges in the differential diagnosis of interdigitating dendritic cell sarcoma of intraparotid lymph node vs. metastatic malignant melanoma with unknown primary site

Interdigitating dendritic cell sarcoma (IDCS) is an uncommon form of malignant histiocytosis affecting dendritic cells. The parotid gland more frequently than other salivary glands has metastasis from extraparotid tumours, which in 80% of cases are melanomas and squamous cell carcinomas. Herein we report our case, a 64-year-old woman who presented with a short history of fluctuating in size swelling below her right ear. Ultrasound scan showed a loculated cystic lesion extending in the parotid parenchyma. Fine needle aspiration (FNA) revealed appearances that were highly suspicious of malignancy, therefore MRI scan was arranged, and parotidectomy planned. The histology of tumour was a malignant spindle cell neoplasm, with immunohistochemical features highly suggestive of metastatic malignant melanoma with divergent differentiation. The challenges in the differential diagnosis of IDCS of intraparotid lymph node vs. metastatic malignant melanoma with unknown primary tumour are described here.

The rarity of this neoplasm figures highlights the importance of describing all new cases putting special emphasis on the steps to be taken in order to shorten the diagnosis, management and treatment process.

Emerging clinical applications of selected biomarkers in melanoma

Melanoma is a lethal skin disease with a mostly predictable clinical course according to a known constellation of clinical and pathologic features. The distinction of melanoma from benign melanocytic nevus is typically unequivocol; however, there is a subset of tumors known for its diagnostic challenges, development of late metastases, and difficulties in treatment. Several melanocytic tissue biomarkers are available that can facilitate the histopathologic interpretation of melanoma as well as provide insight into the biologic potential and mutational status of this disease. This review describes the clinical application of some of these established and emerging tissue biomarkers available to assess melanocytic differentiation, vascular invasion, mitotic capacity, and mutation status. The selected tissue biomarkers in this review include MiTF, Sox10, D2-40, PHH3, H3KT (anti-H3K79me3T80ph), anti-BRAFV600E, and anti-BAP-1.

Value of melanocytic-associated immunohistochemical markers in the diagnosis of malignant melanoma: a review and update

Since the identification of S100 protein as an immunohistochemical marker that could be useful in the diagnosis of melanoma in the early 1980s, a large number of other melanocytic-associated markers that could potentially be used to assist in the differential diagnosis of these tumors have also been investigated. A great variation exists, however, among these markers, not only in their expression in some subtypes of melanoma, particularly desmoplastic melanoma, but also in their specificity because some of them can also be expressed in nonmelanocytic neoplasms, including various types of soft tissue tumors and carcinomas. This article reviews the information that is currently available on the practical value of some of the markers that have more often been recommended for assisting in the diagnosis of melanomas, including those that have only recently become available.

Newly Available Antibodies With Practical Applications in Surgical Pathology

Selected antibodies that have become available in recent years and have applications in diagnostic pathology are discussed. They include antibodies that are organ-related, provide information on cellular differentiation or histogenetic type, have predictive value in tumors, and highlight infective agents. PAX8 (paired box gene 8) is a marker expressed in the lower female genital tract, thyroid, and kidney and their tumors. Napsin A is expressed in the lung and kidney and is an alternative marker for pulmonary adenocarcinoma. Arginase A is a sensitive and specific marker for liver tumors. ERG (Ets-related gene) is an excellent marker for endothelium and vascular tumors as well as prostatic cancer (about 50% of cases). SOX10 (SRY-related HMG box) is expressed predominantly in melanocytic and Schwann cells and the corresponding tumors. DOG1 (discovered on GIST 1) is an excellent marker for gastrointestinal stromal tumor (GIST) and acinic cell carcinoma. OCT3/4 is a pan–germ cell tumor marker, except yolk sac tumor. SALL4 is positive in various types of germ cell tumors, including yolk sac tumor. MUC4 (mucin-related antigen 4) is a sensitive and specific marker for low-grade fibromyxoid sarcoma. Langerin is a specific marker for Langerhans cells and their tumors. SOX11 is a sensitive marker for mantle cell lymphoma. New generation antibodies against anaplastic lymphoma kinase (ALK) are required to reliably demonstrate ALK gene translocation in pulmonary carcinomas. Lack of expression of succinate dehydrogenase B is seen in paragangliomas of the hereditary form and in the pediatric type of GIST. Antibodies against Trepenoma pallidum can facilitate the diagnosis of syphilis, whereas those against SV40 (simian virus 40) are helpful for diagnosis of BK virus infection and progressive multifocal leukoencephalopathy.

Value of SOX10 immunostaining in tumor diagnosis

SOX10 is a transcription factor that is essential for the generation of neural crest cells, their survival, and maintenance of pluripotency. Recent studies have shown that, among tumors, SOX10 is commonly expressed in melanomas, including desmoplastic melanomas, tumors with Schwann cell differentiation, and some salivary gland neoplasms, particularly those with myoepithelial differentiation. Because of its restricted expression, SOX10 has proved to be a useful immunohistochemical marker with a wide range of diagnostic applications in surgical pathology, some of which are briefly reviewed.

Diagnostic utility of neural stem and progenitor cell markers nestin and SOX2 in distinguishing nodal melanocytic nevi from metastatic melanomas

Sentinel lymph node evaluation is a critical component of melanoma staging, and lymph node status provides one of the most powerful predictors of melanoma recurrence and survival. One of the well-known diagnostic pitfalls in melanoma sentinel lymph node evaluation is the presence of nodal melanocytic nevi, which has been demonstrated in up to 26% of lymphadenectomy specimens and specifically in melanoma patients. Melanocytic markers enhance the sensitivity of melanoma detection in sentinel lymph nodes. However, established markers such as anti-melan-A/MART1, S100 protein and SOX10 antibodies cannot discriminate melanoma metastasis from nodal nevi. Recent studies have demonstrated strong expression of neural stem/progenitor cell markers nestin and SOX2 in melanoma. In this study, we tested the diagnostic utility of nestin and SOX2 in differentiating metastatic melanomas from nodal nevi. Twenty-three lymph nodes with metastatic melanomas and 17 with nodal nevi were examined. Of the 23 metastatic melanomas, 18 showed diffuse and strong (3+) nestin, 4 showed rare cells with strong (3+) nestin, and one showed diffuse but faint (1+) nestin staining. Nuclear SOX2 was positive in 13 metastatic melanomas. In contrast, 15 nodal nevi showed no nestin, and 2 showed rare cells with very faint (<1+) nestin staining. SOX2 was negative in 13 nodal nevi. Overall, nestin was strongly expressed in metastatic melanomas (n=22/23; 96%), but not in nodal melanocytic nevi (n=15/17; 88%; P<0.0001). SOX2 was also expressed in metastatic melanomas (n=13/23; 57%) but not in the majority of nodal melanocytic nevi (n=13/16; 81%; P=0.02). In one lymph node harboring metastatic melan-A-negative desmoplastic melanoma, nestin and SOX2 strongly highlighted the infiltrating tumor cells, suggesting the potential clinical value of these two markers in desmoplastic melanoma lymph node biopsies. This study provides evidence that nestin and SOX2 can effectively differentiate nodal melanocytic nevi from metastatic melanomas and serve as powerful diagnostic adjuncts in melanoma staging.

Expression of Sox10 and c-kit in sinonasal mucosal melanomas arising in the Chinese population

Sinonasal mucosal melanomas (SNMM) of the head and neck regions are rare and aggressive malignancies. Although they can affect patients of any ethnicity, they are more numerous in Chinese patients. The diagnosis and treatment of these tumors can be challenging. Recent studies have reported that Sox10 is a sensitive melanocytic marker for cutaneous melanoma (Nonaka et al. in Am J Surg Pathol 32:1291-1298, 2008). In addition, a CD117 (c-kit) gene mutation has been identified in cutaneous melanomas, indicating that there may be potential therapeutic benefits of tyrosine kinase inhibitors, such as Imatinib. The purpose of this study was to detect and test the immunohistochemical expression of Sox10 and c-kit in mucosal melanomas (MM) arising in the nasal cavities of Chinese patients. Twenty eight patients with mucosal melanomas of the nasal cavity were treated in two major hospitals in China. All cases had been locally diagnosed as primary SNMM. We confirmed all diagnoses with positive immunohistochemical stains for S100 and HMB-45. Additionally, automated immunohistochemistry was performed using a goat polyclonal Sox10 antibody and a monoclonal c-kit antibody counterstained using a standard avidin-biotin complex method. Immunohistochemical positive expression of Sox10 was defined by nuclear stain; and positivity for c-kit resulted in a distinct membranous staining. The extent of nuclear positivity for Sox10 and membranous stain for c-kit was graded by 4 board certified pathologists as follows: 1+, 1-25 % of positive tumor cells; 2+, 25-50 %; 3+, 50-75 %; and 4+, ≥75 %. Sox10 nuclear expression was found in all cases (100 %), with 4+ staining in 26 out of 28 cases (92.8 %) and 3+ staining in two cases with (7.1 %). The overall positivity for S100 staining was 23 out of 28 (82.1 %), with 1+ staining in 10 cases, 2+ staining in 6 cases, 3+ staining in 7 cases, and no staining in 5 cases. The sensitivity and intensity of Sox10 immunohistochemistry were both higher than with S100 immunohistochemistry. Immunopositivity of membranous stain for c-kit (CD117) was seen in 24 out of 28 cases (85.7 %), including 6 tumors that were 4+, eight that were 3+, six that were 2+, and four that showed 1+ staining. Our results demonstrate that Sox10 is a sensitive marker for SNMM and it may possess diagnostic value in addition to that of S100 protein. The expression of c-kit in the majority of MMs suggests that it may be useful in the assessment of these tumors for potential treatment with tyrosine kinase inhibitors.

Sox10 is expressed in primary melanocytic neoplasms of various histologies but not in fibrohistiocytic proliferations and histiocytoses

BACKGROUND

Sox10 is a transcription factor associated with neural crest development. Its expression has been reported in melanocytes and peripheral nerve sheath cells and their associated tumors.

OBJECTIVE

To assess Sox10 sensitivity in benign and malignant melanocytic neoplasms of various histologic subtypes and to discern the specificity of Sox10 in distinguishing between melanocytic neoplasms and fibrohistiocytic and histiocytic mimickers.

METHODS

Sox10 expression was examined by immunohistochemistry in 145 cases of formalin-fixed paraffin-embedded tissue, including benign and malignant melanocytic lesions of various histologies and stages (n = 83), fibrohistiocytic and histiocytic lesions (n = 33), and peripheral nerve sheath tumors (n = 19), among others (n = 10).

RESULTS

Immunoreactivity with Sox10 was observed in 100% (83/83) of benign and malignant melanocytic lesions of various subtypes, as well as in 100% (19/19) of benign and malignant peripheral nerve sheath lesions. Among the fibrohistiocytic proliferations and histiocytoses examined, Sox10 was negative in all cases (0/33). Sox10 expression did not vary by histologic subtype in nevi or melanoma; however, both the percentage of tumor nuclei demonstrating Sox10 expression and the intensity of expression were inversely correlated with malignant potential (nevi, melanoma in situ, invasive and metastatic melanoma) (P < .001, P = .016, respectively). Malignant peripheral nerve sheath tumors also showed decreased mean Sox10 expression and decreased intensity of expression when compared with benign counterparts (P < .001, P = .021, respectively).

LIMITATIONS

This is a retrospective study with 145 cases included.

CONCLUSIONS

Sox10 is a highly sensitive marker for melanocytic proliferations and may be useful diagnostically when the differential diagnosis includes fibrohistiocytic and histiocytic proliferations demonstrating S100 expression.

Identification of nodal metastases in melanoma using sox-10

The presence of S100-positive dendritic cells hinders the identification of isolated melanoma tumor cells and micrometastases in sentinel lymph nodes. Sox-10, a transcription factor that plays an important role in schwannian and melanocytic cell development, is not expressed in dendritic cells. We investigated the diagnostic utility of Sox-10 in the identification of metastases in sentinel and nonsentinel lymph nodes for melanoma. We examined the expression pattern of Sox-10, as compared with S100, Melan-A, and HMB-45 in 93 lymph nodes (40 originally reported as positive and 53 originally reported as negative for metastasis) from 33 sentinel lymph node biopsies and regional lymphadenectomies. Sox-10 and S100 both highlighted metastases in 43 of 43 (100%) positive lymph nodes identified in this study; however, Sox-10 immunohistochemical staining significantly improved the detection of nodal metastases. The nuclear staining of Sox-10 promoted improved distinction between heavily pigmented melanophages and melanocytic metastases in 3 positive lymph nodes. In 2 lymph nodes, Sox-10 was critical in distinguishing S100-positive atypical nodal dendritic cells from tumor cells. Also, Sox-10 significantly improved the identification of micrometastases and isolated tumor cells as compared with S100 in 10 positive lymph nodes. Most importantly, Sox-10 identified micrometastases in 2 lymph nodes, originally reported as negative on S100, Melan-A, and HMB-45 immunostains. Therefore, Sox-10 is a comparable marker to S100 in identifying nodal metastases in melanoma and is especially useful in the setting of lymph nodes with heavily pigmented metastases, numerous S100-positive nodal dendritic cells, micrometastases, and isolated tumor cells.

SOX10 expression in superficial spreading and nodular malignant melanomas

SOX10 is a transcription factor expressed in nerve cells and melanocytes. The aim of this study was to investigate the protein expression pattern of SOX10 in malignant melanoma tumors and to analyze whether the results correlated with clinical parameters and the proliferation marker Ki-67. Furthermore, proliferation and migration were analyzed in three different cell lines employing SOX10 small interfering RNA-mediated silencing. Expression patterns were determined in 106 primary tumors and 39 metastases in addition to 16 normal skin samples and six benign nevi employing immunohistochemistry and tissue microarrays. The immunohistochemical staining was evaluated manually and with an automated algorithm. SOX10 was strongly expressed in the benign tissues, but for the malignant tumors superficial spreading melanomas stained stronger than nodular malignant melanomas (P=0.008). The staining intensity was also inversely correlated with T-stage (Spearman's ρ=-0.261, P=0.008). Overall survival and time to recurrence were significantly correlated with SOX10 intensity, but not in multivariate analysis including T-stage. With the automated algorithm there was an inverse correlation between the SOX10 staining intensity and the proliferation marker, Ki-67 (ρ=-0.173, P=0.02) and a significant difference in the intensity signal between the benign tissues, the primary tumors and the metastases where the metastases stained the weakest (P≤0.001). SOX10 downregulation resulted in variable effects on proliferation and migration rates in the melanoma cell lines. In conclusion, the SOX10 intensity level differed depending on the tissue studied and SOX10 might have a role in survival. No conclusion regarding the role of SOX10 for in-vitro proliferation and migration could be drawn.

Sox proteins in melanocyte development and melanoma

Over 10 years have passed since the first Sox gene was implicated in melanocyte development. Since then, we have discovered that SOX5, SOX9, SOX10 and SOX18 all participate as transcription factors that affect key melanocytic genes in both regulatory and modulatory fashions. Both SOX9 and SOX10 play major roles in the establishment and normal function of the melanocyte; SOX10 has been shown to heavily influence melanocyte development and SOX9 has been implicated in melanogenesis in the adult. Despite these advances, the precise cellular and molecular details of how these SOX proteins are regulated and interact during all stages of the melanocyte life cycle remain unknown. Improper regulation of SOX9 or SOX10 is also associated with cancerous transformation, and thus understanding the normal function of SOX proteins in the melanocyte will be key to revealing how these proteins contribute to melanoma.