S100A6 protein expression is different in Spitz nevi and melanomas

The Spectrum of Spitz Melanocytic Lesions: From Morphologic Diagnosis to Molecular Classification

Spitz tumors represent a distinct subtype of melanocytic lesions with characteristic histopathologic features, some of which are overlapping with melanoma. More common in the pediatric and younger population, they can be clinically suspected by recognizing specific patterns on dermatoscopic examination, and several subtypes have been described. We now classify these lesions into benign Spitz nevi, intermediate lesions identified as “atypical Spitz tumors” (or Spitz melanocytoma) and malignant Spitz melanoma. More recently a large body of work has uncovered the molecular underpinning of Spitz tumors, including mutations in the HRAS gene and several gene fusions involving several protein kinases. Here we present an overarching view of our current knowledge and understanding of Spitz tumors, detailing clinical, histopathological and molecular features characteristic of these lesions.

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.

Cutaneous Malignant Melanoma: A Review of Early Diagnosis and Management

Cutaneous melanoma (CM) is a malignant tumor formed from pigment-producing cells called melanocytes. It is one of the most aggressive and fatal forms of skin malignancy. In the last decades, CM's incidence has gradually risen, with 351,880 new cases in 2015. Since the 1960s, its incidence has increased steadily, in 2019, with approximately 96,000 new cases. A greater understanding of early diagnosis and management of CM is urgently needed because of the high mortality rates due to metastatic melanoma. Timely detection of melanoma is crucial for successful treatment, but diagnosis with histopathology may also pose a significant challenge to this objective. Early diagnosis and management are essential and contribute to better survival rates of the patient. To better control this malignancy, such information is expected to be particularly useful in the early detection of possible metastatic lesions and the development of new therapeutic approaches. This article reviews the available information on the early diagnosis and management of CM and discusses such information's potential in facilitating the future prospective.

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.

RAGE Signaling in Melanoma Tumors

Despite recent progresses in its treatment, malignant cutaneous melanoma remains a cancer with very poor prognosis. Emerging evidences suggest that the receptor for advance glycation end products (RAGE) plays a key role in melanoma progression through its activation in both cancer and stromal cells. In tumors, RAGE activation is fueled by numerous ligands, S100B and HMGB1 being the most notable, but the role of many other ligands is not well understood and should not be underappreciated. Here, we provide a review of the current role of RAGE in melanoma and conclude that targeting RAGE in melanoma could be an approach to improve the outcomes of melanoma patients.

Mesenchymal Stem Cell-Secreted Exosome Promotes Chemoresistance in Breast Cancer via Enhancing miR-21-5p-Mediated S100A6 Expression

Emerging evidence has shown the role of mesenchymal stem cell-derived exosome (MSC-exo) in inducing resistance of cancer cells to chemotherapy. However, it remains unclear whether the change of MSC-exo in response to chemotherapy also contributes to chemoresistance. In this study, we investigated the effect of a standard-of-care chemotherapeutic agent, doxorubicin (Dox), on MSC-exo and its contribution to the development of Dox resistance in breast cancer cells (BCs). We found that the exosome secreted by Dox-treated MSCs (Dt-MSC-exo) induced a higher degree of Dox resistance in BCs when compared with non-treated MSC-exo. By analysis of the MSC-exo-induced transcriptome change in BCs, we identified S100A6, a chemoresistant gene, as a top-ranked gene induced by MSC-exo in BCs, which was further enhanced by Dt-MSC-exo. Furthermore, we found that Dox induced the expression of miR-21-5p in MSCs and MSC-exo, which was required for the expression of S100A6 in BCs. Importantly, silencing of miR-21-5p expression in MSCs and MSC-exo abolished the resistance of BCs to Dox, indicating an exosomal miR-21-5p-regulated S100A6 in chemoresistance. Our study thus uncovered a novel mechanistic insight into the role of MSC-secreted exosome in the development of chemoresistance in the tumor microenvironment.

Genomic Landscape of Spitzoid Neoplasms Impacting Patient Management

Spitzoid neoplasms are a distinct group of melanocytic proliferations characterized by epithelioid and/ or spindle shaped melanocytes. Intermediate forms that share features of both benign Spitz nevi (SN) and Spitz melanoma, i.e., malignant Spitz tumor (MST) represent a diagnostically and clinically challenging group of melanocytic lesions. A multitude of descriptive diagnostic terms exist for these ambiguous lesions with atypical Spitz tumor (AST) or Spitz tumor of uncertain malignant potential (STUMP) just naming two of them. This diagnostic gray zone creates confusion and high insecurity in clinicians and in patients. Biological behavior and clinical course of this intermediate group still remains largely unknown, often leading to difficulties with uncertainties in clinical management and prognosis. Consequently, a better stratification of Spitzoid neoplasms in benign and malignant forms is required thereby keeping the diagnostic group of AST/STUMP as small as possible. Ancillary diagnostic techniques such as immunohistochemistry, comparative genomic hybridization, fluorescence in situ hybridization, next generation sequencing, micro RNA and mRNA analysis as well as mass spectrometry imaging offer new opportunities for the distinct diagnosis, thereby allowing the best clinical management of Spitzoid neoplasms. This review gives an overview on these additional diagnostic techniques and the recent developments in the field of molecular genetic alterations in Spitzoid neoplasms. We also discuss how the recent findings might facilitate the diagnosis and stratification of atypical Spitzoid neoplasms and how these findings will impact the diagnostic work up as well as patient management. We suggest a stepwise implementation of ancillary diagnostic techniques thereby integrating immunohistochemistry and molecular pathology findings in the diagnosis of challenging ambiguous Spitzoid neoplasms. Finally, we will give an outlook on pending future research objectives in the field of Spitzoid melanocytic lesions.

Common and not so Common Melanocytic Lesions in Children and Adolescents

The acquired melanocytic nevus is the most common lesion encountered by pediatric pathologists and dermatopathologists in their daily practice. In most cases, there are few difficulties in histopathologic diagnosis. However, it is the acquired melanocytic lesion known as the Spitz nevus, with its intrinsic atypical features which becomes the challenge since it exists along a histopathologic and biologic continuum from the atypical Spitz tumor to spitzoid melanoma. The frustration with some of these spitzoid lesions is that even the "experts" cannot agree as to the differentiation of one from the other even at the level of molecular genetics. Other melanocytic lesions are discussed including the congenital melanocytic nevus with its proliferative nodule(s) and melanoma as the ultimate complication. Although uncommon, cutaneous melanoma in the first 2 decades is emerging as a clinical problem especially in young women in the second decade of life. These are ultraviolet-associated neoplasms whose histopathologic and prognostic features are identical to the adult experience. Considerable progress has been made over the past 15 to 20 years in our understanding of cutaneous melanocytic lesions, but gaps still exist in the important group of spitzoid lesions. It can also be anticipated that more cutaneous melanomas in children will be seen in the future based upon epidemiologic studies.

Affinity Proteomics Exploration of Melanoma Identifies Proteins in Serum with Associations to T-Stage and Recurrence

BACKGROUND

Blood-based proteomic profiling may aid and expand our understanding of diseases and their different phenotypes. The aim of the presented study was to profile serum samples from patients with malignant melanoma using affinity proteomic assays to describe proteins in the blood stream that are associated to stage or recurrence of melanoma.

MATERIAL AND METHODS

Multiplexed protein analysis was conducted using antibody suspension bead arrays. A total of 232 antibodies against 132 proteins were selected from (i) a screening with 4595 antibodies and 32 serum samples from melanoma patients and controls, (ii) antibodies used for immunohistochemistry, (iii) protein targets previously related with melanoma. The analysis was performed with 149 serum samples from patients with malignant melanoma. Antibody selectivity was then assessed by Western blot, immunocapture mass spectrometry, and epitope mapping. Lastly, indicative antibodies were applied for IHC analysis of melanoma tissues.

RESULTS

Serum levels of regucalcin (RGN) and syntaxin 7 (STX7) were found to be lower in patients with both recurring tumors and a high Breslow's thickness (T-stage 3/4) compared to low thickness (T-stage 1/2) without disease recurrence. Serum levels of methylenetetrahydrofolate dehydrogenase 1-like (MTHFD1L) were instead elevated in sera of T3/4 patients with recurrence. The analysis of tissue sections with S100A6 and MTHFD1L showed positive staining in a majority of patients with melanoma, and S100A6 was significantly associated to T-stage.

CONCLUSIONS

Our findings provide a starting point to further study RGN, STX7, MTHFD1L and S100A6 in serum to elucidate their involvement in melanoma progression and to assess a possible contribution to support clinical indications.

Protein gene product 9.5 (PGP9.5) expression in benign cutaneous mesenchymal, histiocytic, and melanocytic lesions: comparison with cellular neurothekeoma

Cellular neurothekeoma (CNTK) frequently enters the differential diagnosis of a benign dermal cellular proliferation. Diagnosis often relies on immunohistochemistry including the use of protein gene product 9.5 (PGP9.5). A previous study demonstrated PGP9.5 expression across a wide variety of soft tissue neoplasms. We explored the utility of this antibody in distinguishing CNTK from other benign dermal-based lesions. A cohort of CNTK (n=7) and benign cutaneous lesions of neural (n=28), fibrohistiocytic (n=23), fibroblastic (n=25), histiocytic (n=18), myofibroblastic (n=7), smooth muscle (n=14), and melanocytic (n=12) differentiations were immunostained with PGP9.5. Staining was graded by H-score and compared with CNTK. A significantly higher H-score was found in CNTK compared with the fibrohistiocytic (p=0.0001), histiocytic (p=0.0016), myofibroblastic (p=0.0003), smooth muscle (p<0.0001), and melanocytic (p=0.0004) groups, with the exceptions of plexiform fibrohistiocytic tumour, xanthoma, and xanthogranuloma. No significant difference was found when comparing CNTK with fibroblastic and neural lesions, with the exceptions of neurofibroma and perineurioma. In conclusion, PGP9.5 is helpful in distinguishing CNTK from most benign cutaneous fibrohistiocytic, histiocytic, myofibroblastic, smooth muscle, and melanocytic lesions. In addition to CNTK and neural lesions, PGP9.5 is also expressed in benign fibroblastic lesions, and therefore distinction of these lesions should not be based on PGP9.5 positivity.

Clear-Cell Atypical Fibroxanthoma: A Combined Immunohistochemistry Analysis

Atypical fibroxanthoma is considered to be a low-grade sarcoma, characterized by a proliferation of bizarre spindled cells. A case of a rare variant of this tumor, a clear-cell atypical fibroxanthoma, presenting with rapid growth on a 63-year-old female, is reported. The differential diagnosis of a clear cell proliferation and a review of the immunohistochemistry markers used in the diagnosis of atypical fibroxanthoma are discussed. In particular, the usefulness of markers such as CD10, procollagen 1, CD68, CD163, CD99, and S100A6, and the importance of negative markers such as S100, cytokeratin, and desmin are emphasized. Furthermore, the development of a keratoacanthoma at the site of previous Mohs surgery is recounted.

The S100 proteins in epidermis: Topology and function

BACKGROUND

S100 proteins are small calcium binding proteins encoded by genes located in the epidermal differentiation complex (EDC). Differently to other proteins encoded by EDC genes, which are indispensable for normal epidermal differentiation, the role of S100 proteins in the epidermis remains largely unknown.

SCOPE OF REVIEW

Particular S100 proteins differ in their distribution in epidermal layers, skin appendages, melanocytes and Langerhans cells. Taking into account that each epidermal component consists of specialized cells with well-defined functions, such differential distribution may be indicative of the function of a given S100 protein. We used this criterion together with the survey of the current experimental data pertinent to epidermis to provide a fairly comprehensive view on the possible function of individual S100 proteins in this tissue.

MAJOR CONCLUSIONS

S100 proteins are differently expressed and, despite extensive structural homology, perform diverse functions in the epidermis. Certain S100 proteins probably ensure constant epidermal renewal and support wound healing while others act in epidermal differentiation or have a protective role. As their expression is differently affected in various skin pathologies, particular S100 proteins could be valuable diagnostic markers.

GENERAL SIGNIFICANCE

S100 proteins seem to be important although not yet fully recognized epidermal constituents. Better understanding of their role in the epidermis might be helpful in designing therapies to various skin diseases.

S100A6 expression in cutaneous smooth muscle neoplasms

The S100A6 protein is expressed in a variety of tissues and distinct staining patterns in S100A6 immunohistochemistry may be useful in the differential diagnosis of difficult lesions. We evaluated the staining pattern of the S100A6 antibody in 22 cases each of pilar leiomyoma (LM), angioleiomyoma (ALM), and cutaneous leiomyosarcoma (LMS). S100A6 labeled both the nucleus and cytoplasm of myocytes in positive cases. About 64% of LM and 86% ALM had positive staining to the S100A6 antibody but predominantly in a weak staining pattern. In contrast, 95% of the LMS exhibited moderate to strong staining with the S100A6 antibody. The difference in the frequency of positive cases was statistically significant in the LM vs LMS comparison (p = 0.025), but we found intensity of staining to be of greatest practical utility. Analysis between the groups taking in to consideration differences in intensity of staining using the nonparametric rank sum (Mann-Whitney U test) demonstrated that there was a statistically significant difference between LM and LMS and between ALM and LMS. Weak or absent S100A6 staining supports a diagnosis of LM, whereas strong positive staining supports a diagnosis of LMS.

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.

A multiplexed, targeted mass spectrometry assay of the S100 protein family uncovers the isoform-specific expression in thyroid tumours

Background

Mounting evidence demonstrates a causal role for S100 proteins in tumourigenesis and several S100 isoforms have shown utility as biomarkers of several types of cancer. The S100 family is comprised of 21 small isoforms, many of them implicated in important cellular functions such as proliferation, motility and survival. Furthermore, in vivo experiments have proven the role of S100 proteins in tumour growth and disease progression, while other studies have shown their prognostic value and involvement in resistance to chemotherapy drugs. Taken together, all these aspects highlight S100 proteins as potential therapeutic targets and as a promising panel of cancer biomarkers. In this work, we have developed a mass spectrometry (MS)-based method for the multiplexed and specific analysis of the entire S100 protein family in tumour tissues and have applied it to investigate the expression of S100 isoforms in the context of thyroid cancer, the main endocrine malignancy.

Methods

Selected Reaction Monitoring (SRM)-MS and stable isotope labelling/label-free analysis were employed to investigate the expression of the 21 S100 protein isoforms in thyroid tissue samples. Specimens included 9 normal thyroid tissues and 27 tumour tissues consisting of 9 follicular adenomas (FA), 8 follicular carcinomas (FTC) and 10 papillary carcinomas (PTC).

Results

The multiplexed and targeted mass spectrometry method led to the detection of eleven S100 protein isoforms across all tissues. Label- and label-free analyses showed the same significant differences and results were confirmed by western blot. S100A6, S100A11 and its putative interaction partner annexin A1 showed the highest overexpression in PTC compared to normal thyroid. S100A13 was also elevated in PTC. Reduced S100A4 expression was observed in FA compared to all other tissues. FA and FTC showed reduction of S100A10 and annexin A2 expression.

Conclusions

Targeted mass spectrometry allows the multiplexed and specific analysis of S100 protein isoforms in tumour tissue specimens. It revealed S100A13 as a novel candidate PTC biomarker. Results show that S100A6, S100A11 and Annexin A1 could help discriminate follicular and papillary tumours. The diagnostic and functional significance of S100A4 and S100A10 reduction in follicular tumours requires further investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1217-x) contains supplementary material, which is available to authorized users.

Atypical Spitzoid neoplasms: a review of potential markers of biological behavior including sentinel node biopsy

Atypical cutaneous melanocytic lesions, including those with Spitzoid features, can be difficult to categorize as benign or malignant. This can lead to suboptimal management, with potential adverse patient outcomes. Recent studies have enhanced knowledge of the molecular and genetic biology of these lesions and, combined with clinicopathological findings, is further defining their biological spectrum, classification, and behavior. Sentinel node biopsy provides important prognostic information in patients with cutaneous melanoma, but its role in the management of melanocytic lesions of uncertain malignant potential (MELTUMP) is controversial. This paper examines the role of molecular testing and sentinel node biopsy in MELTUMPs, particularly atypical Spitzoid tumors.

Cutaneous malignant melanoma: update on diagnostic and prognostic biomarkers

The incidence of cutaneous malignant melanoma has rapidly increased in recent years in all parts of the world, and melanoma is a leading cause of cancer death. As even relatively small melanomas may have metastatic potential, accurate assessment of progression is critical. Although diagnosis of cutaneous malignant melanoma is usually based on histopathologic criteria, these criteria may at times be inadequate in differentiating melanoma from certain types of benign nevi. As for prognosis, tumor (Breslow) thickness, mitotic rate, and ulceration have been considered the most important prognostic indicators among histopathologic criteria. However, there are cases of thin primary melanomas that have ultimately developed metastases despite complete excision. Given this, an accurate assessment of melanoma progression is critical, and development of molecular biomarkers that identify high-risk melanoma in its early phase is urgently needed. Large-scale genomic profiling has identified considerable heterogeneity in melanoma and suggests subgrouping of tumors by patterns of gene expression and mutation will ultimately be essential to accurate staging. This subgrouping in turn may allow for more targeted therapy. In this review, we aim to provide an update on the most promising new biomarkers that may help in the identification and prognostication of melanoma.

S100A6 and c-Kit-Positive Spindle Cell Melanoma of the Dorsal Foot

Spindle cell melanoma, which is a rare form of melanoma, is clinically and histopathologically difficult to diagnose from a variety of nonmelanocytic spindle cell tumors. We describe a 42-year-old Japanese woman with amelanotic melanoma that comprised spindle cells with positive c-kit and S100A6 staining. The use of c-kit and S100A6 might be useful for improving the diagnosis.

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.

MCW melanoma cocktail for the evaluation of micrometastases in sentinel lymph nodes of cutaneous melanoma

Prevailing reports support the status of sentinel lymph node biopsy as the standard of care in the management of cutaneous melanoma. However, the evaluation of sentinel lymph nodes for melanoma metastases with traditionally used immunomarkers such as S100 protein and HMB45 has proved challenging. The MCW melanoma cocktail (a mixture of MART-1 [1:500], Melan-A [1:100] and tyrosinase [1:50] monoclonal antibodies) has demonstrated a highly discriminatory immunostaining pattern. Contrary to conventionally used immunomarkers such as S100 protein, the MCW melanoma cocktail facilitates detection of even singly scattered melanoma cells in sentinel lymph nodes, not only in permanent sections but also in imprint smears.

Update on immunohistochemistry in melanocytic lesions

This article is an up-to-date overview of the potential uses and limitations of immunohistochemistry (IHC) in melanocytic lesions. The information is intended to assist dermatopathologists and dermatologists who read slides to appropriately use IHC in this setting. In addition, dermatologists who do not review microscopic slides will better understand the rationale of the pathologist when reading and interpreting the pathology report.

Spitz nevi and other Spitzoid lesions part I. Background and diagnoses

Spitz nevi are melanocytic proliferations that are characterized by spindled and/or epithelioid nevomelanocytes. First interpreted as juvenile melanoma, these lesions were later characterized as benign and were observed to affect all age groups. Today, contrasting opinions persist regarding the fundamental benignancy versus malignancy within the spectrum of Spitz tumors. Beyond clinical outcome, this controversy has also been fueled by complex and sometimes convoluted classification schemes based on pathologic characteristics. More recently, immunophenotypic and molecular analyses have begun to clarify the etiologic nature of these tumors. Recent evidence suggests that histopathologic features that suggest more aggressiveness in Spitz tumors relate to mitoses and inflammation.

Melanoma update: diagnostic and prognostic factors that can effectively shape and personalize management

Routine light microscopy remains a powerful tool to diagnose, stage and prognose melanoma. Although it is very economical and efficient, it requires a significant level of expertise and, in difficult cases the final diagnosis is affected by subjective interpretation. Fortunately, new insights into the genomic aberrations characteristic of melanoma, coupled with ancillary studies, are further refining evaluation and management allowing for more confident diagnosis, more accurate staging and the selection of targeted therapy. In this article, we review the standard of care and new updates including four probe FISH, the 2009 American Joint Commission on Cancer staging of melanoma and mutant testing of melanoma, which will be crucial for targeted therapy of metastatic melanoma.

Atypical Spitzoid melanocytic tumors: a morphological, mutational, and FISH analysis

BACKGROUND

Identification of the clinical behavior of atypical Spitzoid tumors with conflicting histopathologic features remains controversial.

OBJECTIVE

We sought to assess whether molecular findings may be helpful in the diagnostic and prognostic assessment of atypical Spitzoid tumors.

METHODS

A total of 38 controversial, atypical Spitzoid lesions (≥ 1 mm in thickness) were analyzed for clinicopathological features, chromosomal alterations by fluorescence in situ hybridization (FISH) analysis (RREB1/MYB/CCND1/CEP6), BRAF(V600E) mutation by allele-specific real-time polymerase chain reaction confirmed by sequencing, and H-RAS gene mutation by direct sequencing.

RESULTS

Atypical Spitzoid lesions developed in 21 female and 17 male patients (mean age 22 years). Nine patients underwent sentinel lymph node biopsy and a sentinel lymph node micrometastasis was detected in 4 of these 9 cases. Four additional patients, who did not receive a sentinel lymph node biopsy, experienced bulky lymph node metastases and one experienced visceral metastases and death. Lesions from patients with lymph node involvement showed more deep mitoses (P < .01), less inflammation (P = .05), and more plasma cells (P = .04). FISH analysis demonstrated the presence of chromosomal alterations in 6 of 25 cases. Correlation with follow-up data showed that the only case with fatal outcome showed multiple chromosomal alterations by FISH analysis. BRAF(V600E) mutation was detected in 12 of 16 cases (75%) and H-RAS mutation on exon 3 was found in 3 of 11 cases (27%).

LIMITATIONS

Our results require validation in a larger series with longer follow-up information.

CONCLUSIONS

FISH assay may be of help in the prognostic evaluation of atypical Spitzoid tumors. Diagnostic significance of BRAF(V600E) and H-RAS mutations in this setting remains unclear.

The usefulness of c-Kit in the immunohistochemical assessment of melanocytic lesions

C-Kit (CD117), the receptor for the stem cell factor, a growth factor for melanocyte migration and proliferation, has shown differential immunostaining in various benign and malignant melanocytic lesions. The purpose of this study is to compare c-Kit immunostaining in benign nevi and in primary and metastatic malignant melanomas, to determine whether c-Kit can aid in the differential diagnosis of these lesions. c-Kit immunostaining was performed in 60 cases of pigmented lesions, including 39 benign nevi (5 blue nevi, 5 intradermal nevi, 3 junctional nevi, 15 cases of primary compound nevus, 11 cases of Spitz nevus), 18 cases of primary malignant melanoma and 3 cases of metastatic melanoma. The vast majority of nevi and melanomas examined in this study were positive for c-Kit, with minimal differences between benign and malignant lesions. C-Kit cytoplasmatic immunoreactivity in the intraepidermal proliferating nevus cells, was detected in benign pigmented lesions as well as in malignant melanoma, increasing with the age of patients (P=0.007) in both groups. The patient's age at presentation appeared to be the variable able to cluster benign and malignant pigmented lesions. The percentage of c-Kit positive intraepidermal nevus cells was better associated with age despite other variables (P=0.014). The intensity and percentage of c-Kit positivity in the proliferating nevus cells in the dermis was significantly increased in malignant melanocytic lesions (P=0.015 and P=0.008) compared to benign lesions (compound melanocytic nevi, Spitz nevi, intradermal nevi, blue nevi). Immunostaning for c-Kit in metastatic melanomas was negative. Interestingly in two cases of melanoma occurring on a pre-existent nevus, the melanoma tumor cells showed strong cytoplasmatic and membranous positivity for c-kit, in contrast with the absence of any immunoreactivity in pre-existent intradermal nevus cells. C-Kit does not appear to be a strong immunohistochemical marker for distinguishing melanoma from melanocytic nevi, if we consider c-Kit expression in intraepidermal proliferating cells. The c-Kit expression in proliferating melanocytes in the dermis could help in the differential diagnosis between a superficial spreading melanoma (with dermis invasion) and a compound nevus or an intradermal nevus. Finally, c-Kit could be a good diagnostic tool for distinguishing benign compound nevi from malignant melanocytic lesions with dermis invasion and to differentiate metastatic melanoma from primary melanoma.

Immunohistochemistry in the diagnosis of cutaneous neoplasms

In recent years, there has been a significant increase in the number of diagnostic immunohistochemical stains available to pathologists and dermatopathologists. Immunohistochemistry has become an indispensable tool in dermatopathology, not only in diagnosis but also in the treatment and prognostication of cutaneous neoplasms. In this review we attempt to outline current, as well as new, immunohistochemical stains of relevance in the diagnosis and classification of cutaneous neoplasms.

Diagnostic value of CD163 in cutaneous spindle cell lesions

BACKGROUND

The histologic diagnosis of atypical fibroxanthoma (AFX) can sometimes be challenging. No specific marker exists to confirm the diagnosis other than excluding other entities. CD163 has been shown to have great specificity for tumors of monocyte/histiocyte lineage. In this study, we evaluated the diagnostic utility of CD163 in diagnosing AFX and in identifying skin lesions with histiocytic/dendritic derivation.

METHODS

A total of 157 cases, including 14 AFXs, 5 spindle cell squamous cell carcinomas (SCCs), and 7 spindle cell/desmoplastic melanomas, along with other cutaneous spindle cell and histiocytic/fibrohistiocytic lesions, were stained with CD163.

RESULTS

CD163 was expressed in 11 of 14 (79%) AFXs, with moderate to strong intensity. No staining was observed in cases of spindle cell SCC (0/5) and dermatofibrosarcoma protuberans (0/10). Rare spindle cell/desmoplastic melanomas (2/7) and cutaneous leiomyosarcomas (1/5) demonstrated positive staining. CD163 reactivity was seen in 24 of 29 of benign fibrous histiocytomas (BFHs), including 8 of 8 cellular fibrous histiocytomas and 6 of 9 epithelioid cell histiocytomas. The majority of cutaneous histiocytic lesions, including juvenile xanthogranuloma, Langerhans cell histiocytosis and Rosai-Dorfman disease, were positive for CD163.

CONCLUSION

CD163 is a useful adjunct in distinguishing AFX from other malignant cutaneous spindle cell tumors and offers improved specificity in identifying cutaneous histiocytic/dendritic lesions.

Evaluation of sentinel lymph nodes for melanoma metastases by pathologists

The pathologic evaluation of sentinel lymph nodes for melanoma metastases is not without significant challenges. It is affected by significant variation in approaches, which may compromise the final interpretation, leading to nonrepresentative spurious results. This article discusses various approaches along with recommended dos and don'ts for optimum evaluation of sentinel lymph nodes for melanoma metastases.

Expression patterns of S100 proteins in melanocytes and melanocytic lesions

S100 proteins are differentially expressed in tumours of epithelial origin. Little is known about their expression in melanocyte-derived tumours of neuroectodermal origin. We have analysed the expression of some S100 proteins in this line of lesions using SAGE Genie informatics, cell culture and human tumour tissue. The pattern of expression of six S100 proteins was investigated at both the mRNA and protein levels, using quantitative real-time PCR, western blotting and immunohistochemical analysis. No differential expression was observed with respect to S100A4, S100A7, S100A8, S100A9 and S100A11. In contrast, S100A10 was downregulated in three melanoma cell lines compared with normal melanocytes. Using SAGE informatics, two-dimensional displays of microarray expression data from the NCI60_Novartis cell lines displayed a positive correlation between the expression of S100A10 and the expression of the proliferation marker, Ki67. Our data suggest that S100A10, like its binding partners S100A7 and annexin A2, is an oxidant-sensitive protein. In addition, higher expression of S100A10 was detected in melanocyte cell lines with long projections compared with melanoma cell lines with small ripples. In a panel of 47 melanocyte-derived lesions comprising melanocytic naevi and melanomas, S100A10 was expressed to varying degrees in the melanocytic lesions. The antigen was primarily expressed in regions with a strong proliferating or differentiating capacity, especially in regions in or near the epidermis. We suggest that S100A10 may play a role in the regulation of the proliferation or early maturation sequence of melanocytic lesions, and that it merits further study as a potential biomarker of activity.

Immunohistochemical expression of S100A6 in cellular neurothekeoma: clinicopathologic and immunohistochemical analysis of 31 cases

Neurothekeoma is a term introduced by Gallager and Helwig describing a superficial tumor of purported nerve sheath derivation, with cellular and myxoid types. Recently, it has been suggested that the cellular type does not have nerve sheath differentiation. This subtype represents an uncommon neoplasm and sometimes can be problematic to diagnose because it can be easily mistaken for melanoma. We studied the immunohistochemical features of 31 cases of cellular neurothekeomas to evaluate their immunoprofile. Immunohistochemical studies were performed in all 31 cases with formalin-fixed paraffin-embedded tissue sections with antibodies against S100 protein, S100A6, and melanoma antigen recognized by T-cells (MART-1). In addition, 8 cases were evaluated for HMB-45 antigen, keratin (with a pankeratin cocktail), epithelial membrane (EMA), and smooth muscle antigen (SMA). The lesions were from 8 men and 23 women aged 6-64 years (mean 35 years). Four tumors were located on the nose; 4 scalp; 4 finger; 3 thigh; 2 shoulder; 2 wrist; 2 hand; and 1 each on pelvis, cheek, toe, chest, eyebrow, forearm, penis, axilla, mouth, and leg. All tumors were positive for S100A6 (100%) and negative for cytokeratin, HMB-45 antigen, MART-1, and EMA (100%); 29 cases were negative for S100 protein (93.5%; the 2 positive cases had only scattered cells labeled), and only 2 cases were focally positive for SMA (7.5%). Therefore, the combination of strong immunoreactivity for S100A6, in nested dermal spindle cell proliferations, and lack of S100 protein or keratin, supports a diagnosis of cellular neurothekeoma.