S100A6 expression in fibrohistiocytic lesions

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.

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.

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.

Immunohistochemical markers in fibrohistiocytic lesions: factor XIIIa, CD34, S-100 and p75

BACKGROUND

The distinction between dermatofibroma (DF), dermatofibrosarcoma protuberans (DFSP), and other benign and malignant cutaneous spindle cell lesions frequently requires immunohistochemical staining. CD34 and factor XIIIa are the most commonly used immunostains; however, they may exhibit aberrant expression and introduce the potential for misdiagnosis. There is some data supporting that p75 and S100A6 may be additional helpful immunohistochemical markers.

METHODS

We undertook a large case series examining the use of CD34 and factor XIIIa as well as p75 and S100A6 in DF, cellular DF, DFSP, indeterminate fibrohistiocytic lesion, and scar.

RESULTS

As expected, CD34 stained DFSP, although it was usually negative in DF. Factor XIIIa was generally positive in DF and negative in DFSP. There were exceptions in both cases of DF and DFSP. S100A6 was routinely negative in all entities studied. P75 was negative in all cases except DFSP, approximately half of which showed weak and/or patchy positivity.

CONCLUSIONS

We conclude that to date, CD34 and factor XIIIa remain the most reliable immunohistochemical markers for DF and DFSP.

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.

Quantitative proteomic analysis of dexamethasone-induced effects on osteoblast differentiation, proliferation, and apoptosis in MC3T3-E1 cells using SILAC

SUMMARY

The impairment of osteoblast differentiation is one cause of the glucocorticoid-induced osteoporosis (GCOP). The quantitative proteomic analysis of the dexamethasone (DEX)-induced effects of osteoblast differentiation, proliferation, and apoptosis using stable-isotope labeling by amino acids in cell culture (SILAC) demonstrated drastic changes of some key proteins in MC3T3-E1 cells.

INTRODUCTION

The impairment of osteoblast differentiation is one of the main explanations of GCOP. SILAC enables accurate quantitative proteomic analysis of protein changes in cells to explore the underlying mechanism of GCOP.

METHODS

Osteoprogenitor MC3T3-E1 cells were treated with or without 10(−6) M DEX for 7 days, and the differentiation ability, proliferation, and apoptosis of the cells were measured. The protein level changes were analyzed using SILAC and liquid chromatography-coupled tandem mass spectrometry.

RESULTS

In this study, 10(−6) M DEX inhibited both osteoblast differentiation and proliferation but induced apoptosis in osteoprogenitor MC3T3-E1 cells on day 7. We found that 10(−6) M DEX increased the levels of tubulins (TUBA1A, TUBB2B, and TUBB5), IQGAP1, S100 proteins (S100A11, S100A6, S100A4, and S100A10), myosin proteins (MYH9 and MYH11), and apoptosis and stress proteins, while inhibited the protein levels of ATP synthases (ATP5O, ATP5H, ATP5A1, and ATP5F1), G3BP-1, and Ras-related proteins (Rab-1A, Rab-2A, and Rab-7) in MC3T3-E1 cells.

CONCLUSIONS

Several members of the ATP synthases, myosin proteins, small GTPase superfamily, and S100 proteins may participate in functional inhibition of osteoblast progenitor cells by GCs. Such protein expression changes may be of pathological significance in coping with GCOP.

Differential gene expression profiles of neurothekeomas and nerve sheath myxomas by microarray analysis

Neurothekeomas and dermal nerve sheath myxomas have previously been considered related cutaneous neoplasms of peripheral nerve sheath origin based on light microscopic similarities. However, recent immunohistochemical and ultrastructural data indicate nerve sheath myxomas exhibit true nerve sheath differentiation, whereas no such compelling evidence exists for neurothekeomas. Although neurothekeomas lack a specific immunohistochemical profile, similar antigen expression and histopathologic patterns suggest neurothekeomas may be categorized as fibrohistiocytic tumors. To date, no known molecular studies have examined the histogenetic relationship of these tumors. We report the first microarray-based gene expression profile study of these entities on formalin-fixed paraffin-embedded tissues. Cases of dermal schwannomas, dermal nerve sheath myxomas, myxoid/mixed/cellular neurothekeomas, and cellular fibrous histiocytomas diagnosed in the past 3 years were identified in our database. Archival formalin-fixed paraffin-embedded tissue from 28 patients was selected for microarray analysis (seven schwannomas, five nerve sheath myxomas, nine myxoid/mixed/cellular neurothekeomas and seven cellular fibrous histiocytomas). Following tumor RNA isolation, amplification and labeling using commercially available kits, labeled targets were hybridized to the Affymetrix GeneChip Human Genome U133 Plus 2.0 Array (Santa Clara, CA, USA). Acquisition of array images and data analyses was performed using appropriate software. Hierarchical clustering and principal component analysis demonstrated discrete groups, which correlated with histopathologically identified diagnoses. Dermal nerve sheath myxomas demonstrate very similar molecular genetic signatures to dermal schwannomas, whereas neurothekeomas of all subtypes more closely resemble cellular fibrous histiocytomas. We are the first to report distinct gene expression profiles for nerve sheath myxomas and neurothekeomas, which further substantiates the argument that these are separate entities. Our molecular data confirms that dermal nerve sheath myxomas are of peripheral nerve sheath origin, and suggests that neurothekeomas may actually be a variant of fibrous histiocytomas.

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.

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.

S100A6 expression and function in human osteosarcoma

There is a critical need to identify markers that can accurately identify existing or predict future metastatic disease in patients with osteosarcoma since the majority of patients present with undetectable micrometastatic disease. We previously reported S100A6 is overexpressed in human osteosarcoma and increased expression of S100A6 by immunohistochemistry correlated with decreased clinical metastasis. We have established 11 primary cultures from biopsies of patients with osteosarcoma and ten of the 11 primary cultures have increased expression of S100A6 relative to normal human osteoblasts. To further explore possible mechanisms for metastasis suppression previously reported, we used in this report siRNA-mediated knockdown of S100A6 in four commonly used human osteosarcoma lines, then examined their cell adhesion, migration, and invasion properties. Knockdown of S100A6 expression inhibited cell adhesion and promoted cell migration and invasion in these lines. Conversely, S100A6 overexpression enhanced cell adhesion and inhibited cell invasion. Our data demonstrate S100A6 is commonly overexpressed in human osteosarcoma. S100A6 may inhibit osteosarcoma metastasis by promoting cell adhesion and inhibiting cell motility and invasion. Thus, S100A6 may be considered a potential marker for human osteosarcoma with prognostic value for identifying patients without metastases.

Expression of S100A6 protein in a broad spectrum of cutaneous tumors using tissue microarrays

BACKGROUND

S100A6, a calcium-binding protein in the S100 family, has been observed in melanocytic nevi, neural tumors, fibrohistiocytic tumors and is overexpressed in melanoma. Previous studies reported S100A6 expression in atypical fibroxanthomas (AFX) but not in a small number of desmoplastic melanomas (DM). Limited data on S100A6 expression in cutaneous epithelial tumors exists in the literature. The goal of this study was to determine the specificity and sensitivity of S100A6 protein in a spectrum of cutaneous mesenchymal or epithelial tumors.

METHODS

Tissue microarrays of cutaneous epithelial neoplasms, mesenchymal neoplasms, DM and malignant peripheral nerve sheath tumors (MPNST) were stained with S100A6 antibody.

RESULTS

Eleven basal cell carcinomas (BCC) failed to express S100A6, whereas all 10 squamous cell carcinomas (SCC) expressed S100A6. Four of seven microcystic adnexal carcinomas (MAC) stained for S100A6. Tumors with duct differentiation variously expressed S100A6 protein, with two hidradenomas showing the strongest staining. Malignant spindle cell tumors, with the exception of 13 of 30 MPNST, had a high incidence of S100A6 positivity.

CONCLUSIONS

S100A6 expression may distinguish SCC from BCC, MAC from BCC and hidradenoma from other adnexal tumors. S100A6 expression favors DM over MPNST but overlap limits its diagnostic use.

Increased expression of S100A6 is associated with decreased metastasis and inhibition of cell migration and anchorage independent growth in human osteosarcoma

While most osteosarcoma patients have metastatic or micrometastatic lesions, less than 15% of them have clinically detectable metastatic diseases at presentation. To identify potential markers that may predict osteosarcoma metastasis, we analyzed the expression of S100A6 in 50 osteosarcoma cases and found that 84% of the analyzed specimens stained positive for S100A6. There is a trend towards decreased clinically evident metastasis with increased S100A6 staining. Overexpression of S100A6 in osteosarcoma cells decreases cell motility and anchorage independent growth on collagen gels. Our findings provide evidence that, while S100A6 is commonly overexpressed in human osteosarcoma, loss of its expression correlates with a metastatic phenotype.

Cellular neurothekeoma with histiocytic differentiation

BACKGROUND

It is generally accepted that the two types of neurothekeoma (myxoid type and cellular type) represent the two poles of a spectrum. This concept, however, has recently been challenged, and cellular neurothekeomas have been suggested as a separate classification and are included in the "fibrohistiocytic" category by some authors. Cellular neurothekeomas have been reported to show negative immunohistochemical staining for histiocytic markers, and PG-M1 is now considered to be the most reliable histiocytic marker.

CASE REPORT

We report a case of cellular neurothekeoma. The histopathological features in this case were typical for cellular neurothekeoma. Immunohistochemically, the neoplastic cells were diffusely positive for S-100A6 protein, PGP9.5, CD10, CD68 (KP1), PG-M1, and Vimentin, and negative for other antibodies including S-100 protein and factor XIIIa.

CONCLUSIONS

Cellular neurothekeoma expressing both KP-1 and PG-M1 is considered to show histiocytic differentiation, and may be interpreted as a neoplasm with immature nerve sheath differentiation, incidentally expressing histiocytic markers, or as an undifferentiated neoplasm derived from the neural crest cells of nerve sheath/fibrohistiocyte lineage. These results, such as the concomitant expressions of PGP9.5/S-100A6 and PG-M1/CD68 (KP-1), support the theory of multiple differentiation in cellular neurothekeomas. The significance of the expression of CD10 in this cellular neurothekeoma is unclear.

Primary purely intradermal pleomorphic liposarcoma

INTRODUCTION

Pleomorphic liposarcoma (PLPS) is a high-grade pleomorphic sarcoma, containing multivacuolated lipoblasts, which usually develops during late adult life. It usually occurs in the deep soft tissues and uncommonly arises in the subcutis, the dermis representing an exceedingly rare site of occurrence.

METHODS

We describe a case of PLPS arising in the dorsal aspect of the nose of a 75-year-old woman. Preoperative duration was 9 months.

RESULTS

The lesion was intradermal well-circumscribed, dome-shaped, measuring 1.2 cm. It fulfilled the histologic criteria for inclusion in the PLPS category. The tumor cells focally expressed calretinin. A review of the literature yielded four cases documented, to which we add the present report. All the patients were adults with a mean age of 67 (range 39-95) years, and three of five cases arose on the scalp. Local recurrence occurred in one patient, but no distant metastases or disease-related deaths were observed.

CONCLUSION

PLPS very rarely arises in the dermis. In spite of high-grade morphology, the intradermal tumor shows a relatively favorable prognosis. Diagnostic consideration includes pleomorphic lipoma, clear cell atypical fibroxanthoma, balloon cell melanoma, and metastatic clear cell carcinoma of renal origin. Recognition of this distinctive and rare type of liposarcoma is essential to avoid under- or misdiagnosis and inappropriate treatment.

S100A6 protein expression is different in Spitz nevi and melanomas

The Spitz nevus is a benign melanocytic lesion that can be identified reliably in many cases by conventional histopathological criteria. However, there are subsets of Spitz nevi and of malignant melanoma that closely resemble each other and represent diagnostic challenges. S100 proteins are of interest because of their involvement in neoplastic processes and their genes are clustered in chromosome 1q21. Chromosome 1 contains mutations in several types of tumors, including melanomas. The expression of different S100 proteins (A2, A6 and A8/A9 or A12) was examined in 42 Spitz nevi, 105 melanomas, and 73 melanocytic nevi to test the hypothesis that their expression differs among these entities and may contribute to the distinction between these entities. The results showed an up-regulation of S100A6 protein in Spitz nevi, melanomas, and melanocytic nevi but with a different percentage of positivity and pattern of immunoreactivity. The differences between these three entities were statistically significant (P <.001). All 42 Spitz nevi (100%) showed strong and diffuse S100A6 protein expression, both in junctional and in dermal components of the nevi. Thirty-three percent of melanomas expressed S100A6 (35/105). The expression was mainly weak (30/35) and patchy in the dermal component and was negative or minimal in the junctional component. Fifty-six percent of different subtypes of melanocytic nevi (41/73) expressed S100A6, almost all of them weakly (40/41) and in the dermal component. Normal intraepidermal melanocytes were negative. The melanocytic cells in these three entities did not express S100A2, S100A8/A9 or A12. However, an up-regulation of S100A2 and S100A8/A9 or A12 proteins was observed in normal keratinocytes in the epidermis overlying Spitz nevi and melanomas, without differences. In summary, a simple immunohistochemical test for S100A6 protein differentiated between Spitz nevi, melanomas, and melanocytic nevi. This marker could be used when the distinction is very difficult or controversial in routine studies, especially when there is a junctional component. Further molecular analyses of the S100A6 protein and gene should be performed to study the underlying genetic bases for such differences.

S100A protein expression in the distinction between lentigo maligna and pigmented actinic keratosis

Lentigo maligna (LM), a type of malignant melanoma in situ, and pigmented actinic keratosis (PAK) may have similar clinical appearances but are different in prognosis and treatment. Diagnosis is established by skin biopsy. In certain cases, microscopic features may be very similar in both entities, making it difficult to determine whether the pigmented atypical cells are keratinocytes or melanocytes. Immunohistochemical markers can be useful for the identification of melanocytes in these cases. There are limitations to the use of some standard immunohistochemistry markers, however. S100 proteins are a varied group of proteins that are of special interest because of their dysregulated expression in neoplastic disorders. Their expression is changed during malignant transformation, progression, and/or metastasis in various cell lines and tumors, including melanomas. Our study analyzed the expression of several of the S100 protein subtypes (S100A2, S100A6, and S100A8/A9 or A12) in 38 LM cases and 44 PAK cases to define their potential value in the distinction between these entities together with their role in the development of early malignant melanoma of the skin. The results showed an upregulation of S100A2 protein in atypical keratinocytes in PAK and in normal keratinocytes adjacent to melanoma cells in LM. There was also an upregulation of S100A8/A9 or A12 protein, as detected by the antibody MAC387, in normal keratinocytes adjacent to both atypical keratinocytes and melanocytes in PAK and LM, respectively. There were statistically significant differences in the level of positive cells and in the pattern of immunoreactivity for anti-S100A2 and MAC387 in each entity, however. Moreover, the findings of our study support the notion that melanocyte-keratinocyte interactions are abnormal in both of these disease entities and may be involved in their progression.

Antibody to S100a6 protein is a sensitive immunohistochemical marker for neurothekeoma

BACKGROUND

Neurothekeoma is a benign tumor of putative peripheral nerve sheath origin. It occurs in a myxoid (classic) variant, cellular variant, and intermediate (mixed) variant. Cellular neurothekeoma (CNT) usually involves the head and neck or extremities of young patients. Histologically, CNT can be confused with melanocytic and fibrohistiocytic lesions. An immunohistochemical antibody panel is often necessary to confirm the histological impression and exclude melanocytic and/or fibrohistiocytic lesions.

METHODS

Formalin-fixed, paraffin-embedded archival tissues were evaluated by immunohistochemistry using antibodies specific for S100A6 and PGP9.5 in 11 cases of neurothekeoma (seven cellular, four myxoid). A variety of other antibodies were evaluated by immunohistochemistry at the time of initial diagnosis.

RESULTS

All 11 neurothekeoma cases were positive for S100A6 protein (four cases, weak/1+; seven cases, strong/2+), corresponding to 100% sensitivity. In contrast, eight of 11 neurothekeoma cases (73% sensitivity) were positive for PGP9.5. All seven CNT cases were negative for S100B, as expected.

CONCLUSIONS

Anti-S100A6 is a highly sensitive antibody for neurothekeomas, including CNT, and, in our experience, is superior in sensitivity to PGP9.5. However, like other antibodies used in evaluating neurothekeomas, S100A6 lacks specificity, as has been demonstrated in previous studies. Nevertheless, S100A6 can be useful in an immunohistochemical antibody panel to evaluate lesions where the differential diagnosis includes CNT.