The use and application of special techniques in assessing melanocytic tumours

Effect of the Stromal Vascular Fraction on Changes in Melanin Formation in B16 Cells Treated by IBMX

OBJECTIVE

To investigate the effect of the stromal vascular fraction (SVF) on changes in melanin formation and tyrosinase activity in B16 cells treated by 3-isobutyl-1 methylxanthine (IBMX) and to explore the mechanism of SVF-mediated inhibition of pigmentation.

METHODS

We co-cultured extracted SVFs and B16 cells treated with IBMX in a certain proportion, and the marker molecule HMB-45 was detected by immunochemistry. Melanin content was determined by NaOH lysis. Activity of tyrosinase was measured by the DOPA oxidation method.

RESULTS

HMB-45 was commonly expressed in B16 cells induced by IBMX. After the addition of SVFs, the expression of HMB-45 decreased significantly and positively correlated with increases in SVFs. After the induction of B16 cells by IBMX, melanin content increased significantly. However, melanin decreased after SVF and B16 co-culturing; the effect was more substantial with the increase and decrease in SVFs, and the activity of tyrosinase decreased.

CONCLUSION

SVFs inhibit the production of melanin and reduce the activity of tyrosinase, possibly providing a new breakthrough for the treatment of pigment disorders.

NO LEVEL ASSIGNED

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Tyrosinase and nestin immunohistochemical expression in melanocytic nevi as a histopathologic pattern to trace melanocyte differentiation and nevogenesis

While histological analysis represents a powerful tool for the classification of melanocytic lesions as benign or malignant, a clear-cut distinction between a nevus and a melanoma is sometimes a challenging step of the diagnostic process. The immunohistochemical detection of tyrosinase, cardinal melanogenic enzyme during melanocytic maturation, has often been helpful in formulating a differential diagnosis due to the peculiar staining pattern in nevocytes compared with melanoma cells. Tyrosinase distribution in nevi appears to overlap with the cytoarchitectural changes observable within these lesions, that result in epidermal or superficial dermal nevocytes being larger and strongly expressing melanocytic differentiation antigens, such as tyrosinase, compared with deeper dermal nevus cells. Our study aimed to evaluate the immunohistochemical expression pattern of tyrosinase in different histological types of acquired dysplastic melanocytic nevi, including junctional, compound, and intradermal nevi. Moreover, to estimate whether in nevocytes the expression of tyrosinase was associated with their differentiation state, we investigated the expression of two recognized markers of pluripotency, CD34 and nestin. In all examined nevi, our analysis revealed a remarkable immunoreactivity for tyrosinase in junctional and superficial dermal nevocytes and a decreasing gradient of staining in dermal nevocytes, up to become negative in deeper dermis. Meanwhile, junctional and dermal nevocytes were lacking in CD34 protein. Furthermore, nestin immunostaining showed an opposite distribution compared with tyrosinase, leading us to look into the tyrosinase/nestin expression pattern in melanocytic nevus as a tool to better understand the final stages of differentiation of melanocyte precursors toward their ultimate anatomical site into the epidermis.

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.

Marginal and joint distributions of S100, HMB-45, and Melan-A across a large series of cutaneous melanomas

CONTEXT

The distribution of the standard melanoma antibodies S100, HMB-45, and Melan-A has been extensively studied. Yet, the overlap in their expression is less well characterized.

OBJECTIVES

To determine the joint distributions of the classic melanoma markers and to determine if classification according to joint antigen expression has prognostic relevance.

DESIGN

S100, HMB-45, and Melan-A were assayed by immunofluorescence-based immunohistochemistry on a large tissue microarray of 212 cutaneous melanoma primary tumors and 341 metastases. Positive expression for each antigen required display of immunoreactivity for at least 25% of melanoma cells. Marginal and joint distributions were determined across all markers. Bivariate associations with established clinicopathologic covariates and melanoma-specific survival analyses were conducted.

RESULTS

Of 322 assayable melanomas, 295 (91.6%), 203 (63.0%), and 236 (73.3%) stained with S100, HMB-45, and Melan-A, respectively. Twenty-seven melanomas, representing a diverse set of histopathologic profiles, were S100 negative. Coexpression of all 3 antibodies was observed in 160 melanomas (49.7%). Intensity of endogenous melanin pigment did not confound immunolabeling. Among primary tumors, associations with clinicopathologic parameters revealed a significant relationship only between HMB-45 and microsatellitosis (P = .02). No significant differences among clinicopathologic criteria were observed across the HMB-45/Melan-A joint distribution categories. Neither marginal HMB-45 (P = .56) nor Melan-A (P = .81), or their joint distributions (P = .88), was associated with melanoma-specific survival.

CONCLUSIONS

Comprehensive characterization of the marginal and joint distributions for S100, HMB-45, and Melan-A across a large series of cutaneous melanomas revealed diversity of expression across this group of antigens. However, these immunohistochemically defined subclasses of melanomas do not significantly differ according to clinicopathologic correlates or outcome.

Immunohistochemical Expression of Melanocytic Antigen PNL2, Melan A, S100, and PGP 9.5 in Equine Melanocytic Neoplasms

The immunoreactivity of PNL2, Melan A, and protein gene product (PGP) 9.5 was compared with that of S100 protein in 50 formalin-fixed, paraffin-embedded equine melanocytic neoplasms. PNL2, PGP 9.5, and S100 protein were detected in all 50 neoplasms; none expressed Melan A. PNL2 was not expressed in 62 nonmelanocytic tumors (equine sarcoids, schwannomas, carcinomas, sarcomas, endocrine tumors, sex-cord stromal tumors, germ cell tumors, and leukocytic tumors) or in normal tissues other than epidermis. In summary, antibody PNL2 is a sensitive marker of equine melanocytic neoplasms and is more specific than S100 protein or PGP 9.5. In contrast, the monoclonal antibody to Melan A did not react with any of the equine melanomas.

Primary oral melanoma: a histopathological and immunohistochemical study of 22 cases of Latin America

OBJECTIVE

The aim of this study was to analyze the histopathological and immunohistochemical characteristics of 22 cases of primary oral melanomas (OM).

STUDY DESIGN

Twenty two cases of primary oral melanoma were analyzed by description of their histopathological features and immunohistochemical study using the antibodies S-100, HMB-45, Melan-A and Ki-67.

RESULTS

The mean age was 58 years and 14 cases were female. The main affected sites were the hard palate, followed by the upper gingiva. Microscopically, 15 cases presented level III of invasion, 2 cases were amelanotic and 13 showed a mixed epithelioid and plasmacytoid or spindle cells composition. Some cases showed necrosis, perivascular and perineural invasion. S-100 and HMB-45 were positive in all cases, but 3 cases were negative for Melan-A. The proliferative index with Ki-67 was high, with labeling index ranging from 15.51% to 63% of positive cells.

CONCLUSION

S-100 and HMB-45 are more frequently expressed than Melan-A in primary oral melanomas and these markers are helpful to confirm the diagnosis.

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.

Immunohistochemical Identification of Canine Melanocytic Neoplasms With Antibodies to Melanocytic Antigen PNL2 and Tyrosinase

The immunoreactivity of PNL2 and antityrosinase in formalin-fixed, paraffin-embedded canine melanocytic neoplasms ( n = 101) was compared with that of Melan A. Of the 113 samples overall, 106 were positive for PNL2, 101 for Melan A, and 90 for tyrosinase. Six melanomas that were positive for PNL2 were negative for Melan A; 1 melanoma that was negative for PNL2 was positive for Melan A. Eighty tumors were positive for all 3 markers; 111 reacted with at least 1 the 3 antibodies. Decalcification with formic acid for up to 1 week did not affect immunoreactivity of any of the markers; however, decalcification with HCl for 1 day or 1 week notably decreased or completely abrogated immunoreactivity for Melan A and PNL2. There was only minor loss of immunoreactivity for tyrosinase in tissues decalcified with HCl for 1 week. Prolonged fixation (up to 2 months) did not affect PNL2 or tyrosinase immunoreactivity; however, Melan A immunoreactivity was reduced after 1 month of fixation. PNL2 was not expressed in 120 nonmelanocytic tumors (carcinomas, sarcomas, steroid-producing tumors, and leukocytic tumors). In summary, antibody PNL2 is slightly more sensitive than Melan A and more sensitive than tyrosinase in the identification of canine melanocytic neoplasms. Furthermore, PNL2 does not appear to cross-react with nonmelanocytic neoplasms. PNL2 is resistant to prolonged fixation but sensitive to strong decalcification. Results indicate that PNL2 is an excellent marker in the identification of canine melanomas and that the sensitivity is close to 100% when used in conjunction with Melan A and tyrosinase.

Expression of the embryonic morphogen Nodal in cutaneous melanocytic lesions

Nodal, a potent embryonic morphogen in the transforming growth factor-beta family, is a proposed key regulator of melanoma tumorigenicity. However, there has been no systematic study of Nodal expression in melanocytic lesions. We investigated Nodal expression by immunohistochemistry in 269 melanocytic lesions, including compound nevi, dysplastic nevi, congenital nevi, Spitz nevi, melanoma in situ, malignant melanoma including the variant desmoplastic melanoma, and metastatic melanoma. We found that the Nodal expression was significantly increased in malignant lesions (including melanoma in situ, malignant melanoma, and metastatic melanoma) compared with compound nevi, Spitz nevi, and dysplastic nevi. Surprisingly, congenital nevi expressed a level of Nodal comparable with malignant lesions, whereas desmoplastic melanoma showed lower expression than nondesmoplastic malignant melanoma (P<0.05). Deep melanoma (Breslow depth >1 mm) displayed a higher percentage of Nodal-positive tumor cells than did superficial melanoma (Breslow depth < or =1 mm), although there was no statistical difference in the overall staining intensity (P=0.18). Melanomas in situ showed a lower level of Nodal expression than did deep melanomas and metastatic melanomas (P<0.05). The low expression of Nodal in normal and dysplastic nevi, and its increasing expression with the progression of malignant lesions, are suggestive of a role for Nodal in melanoma progression.

The correlation of TRPM1 (Melastatin) mRNA expression with microphthalmia-associated transcription factor (MITF) and other melanogenesis-related proteins in normal and pathological skin, hair follicles and melanocytic nevi

BACKGROUND

Melastatin (TRPM1), a.k.a. transient receptor potential cation channel, subfamily M, member 1 (TRPM-1) regulates melanocyte differentiation and proliferation. TRPM1 is transcriptionally regulated by the essential melanocyte transcription factor MITF (microphthalmia-associated transcription factor). For the most part, MITF expression is preserved during melanoma progression, while TRPM1 mRNA expression decreases or is completely lost. The loss of TRPM1 is associated with melanomas that are more aggressive.

OBJECTIVE

To assess the relationship between TRPM1 mRNA expression and the expression of MITF and nine other markers of melanocytes and melanin-related proteins by immunohistochemistry in normal skin, scars, hair follicles and ordinary melanocytic nevi.

METHODS

Samples of normal skin (n = 102; from tumor excisions and plastic procedures), scars (n = 5; from re-excision specimens) and compound melanocytic nevi (n = 4) were evaluated for the presence of TRPM1 mRNA transcripts as detected by chromogenic in situ hybridization (CISH). Immunohistochemical techniques were used to detect melanin-related proteins including: MITF, S100 protein, Mart-1, tyrosinase, Mel5, HMB45, tyrosinase-related protein-1 (TRP1), TRP2 and alpha-melanocyte stimulating hormone (alphaMSH). The labeling index (LI) was defined as the number of intraepidermal cells expressing mRNA or protein per one hundred basal keratinocytes.

RESULTS

A wide range of LI was found for all markers (0-33 positive cells/100 keratinocytes). When these LI were compared, no significant differences in the expression of MITF, S100, Mart1, tyrosinase proteins and TRPM1 mRNA were identified. The LI for TRPM1 mRNA expression ranged from 74% of that for MITF to 86% for tyrosinase. The LI for TRP-1, TRP-2 and Mel5 was similar to that of TRPM1, while HMB-45 had a significantly lower LI than all other markers. TRPM1 mRNA correlated most tightly with MITF and tyrosinase expression (r = 0.81 and 0.68, respectively, both p = 0.0001). Likewise, the strongest correlation among all the melanin-related proteins existed between tyrosinase and MITF (r = 0.79, p = 0.0001). There was variable expression of melanin-related proteins when LI were analyzed by anatomic site, patient age, extent of sun-damage and proximity to a melanocytic tumor. Anogenital skin showed the highest and acral skin the lowest LI for TRPM1, MITF, S100 protein, Tyrosinase, Mel5 and HMB45. Advanced age (> 60 years) was associated with decreased TRPM1 expression. Sun-damaged skin exhibited significantly increased LI as measured by MITF, S100 protein, Mart1, tyrosinase and HMB-45, but no differences for TRPM1. However, the MITF-TRPM1 differential (i.e. MITF LI-TRPM1 LI = MITF+TRPM1--melanocytes) was significantly increased in site-matched skin (4.6 +/- 4.4 vs. 1.5 +/- 2.5, p = 0.01). There was a suggestion of reduced LI in normal skin in the proximity of melanoma (from melanoma re-excision specimens) for S100, HMB45 and TRPM1 mRNA. TRPM1 LI was significantly decreased in scars compared to normal skin (5.6 +/- 1.4 vs. 9.7 +/- 4.3, p = 0.02), this was reflected in an increase in the MITF-TRPM1 differential (9.6 +/- 7.5 vs. 3.2 +/- 3.1, p = 0.0001). MITF LI were consistently higher than MSLN LI at all levels of the hair follicle; notably, MITF was expressed by isthmic-bulge cells. In ordinary melanocytic nevi, MITF and TRPM1 expression decreased with melanocyte descent: there was more signal for both markers in superficial epithelioid type A melanocytes than deeper type C melanocytes.

CONCLUSIONS

By CISH, TRPM1 mRNA expression is specific for melanocytes and strongly associated with MITF and tyrosinase expression, the latter implicating a mature melanocyte phenotype. However, in normal skin, TRPM1 mRNA expression appears to be dynamic, labeling most but not all melanocytes, with variable expression ostensibly related to local environmental factors.

A Novel Immunohistochemical Marker of Normal and Neoplastic Melanocytes in Formalin-fixed, Paraffin-embedded Tissues of Albino Rats

In albino rats, spontaneous occurrence of melanocytic tumors is rare, with diagnosis difficult. This study evaluated immunoreactivity for PNL2 in normal and neoplastic melanocytes in formalin-fixed and paraffin-embedded tissues of albino rats. The samples consisted of 11 (1.57%) amelanotic melanomas in 700 rats (2 studies), 23 non-melanocytic tumors, and a wide variety of normal tissues. In normal albino rats, PNL2 stained the melanocytes in the iris and choroid of the eyeball and the hair bulb and basal cell layers of the epidermis of the whole body. In amelanotic melanoma, the tumor cells consisted of spindle cells with eosinophilic cytoplasm without melanin granules. PNL2 consistently stained cytoplasm in all amelanotic melanoma cells. In contrast, the nonmelanocytic tumor cells were not labeled. Electron microscopically, neoplastic, and normal melanocytes showed numerous cytoplasmic premelanosomes (stage II melanosome). In conclusion, PNL2 is direct against a fixative-and decalcific-resistant melanocyte-associated antigen, and has high specificity against normal and neoplastic melanocytes of albino rats.

Differential Expression of Melanocytic Markers in Myoid, Lipomatous, and Vascular Components of Renal Angiomyolipomas

Context.—Renal angiomyolipoma is a tumor composed of varying amounts of fat, smooth muscle, and blood vessels. Characteristically, tumor cells express melanocytic markers such as HMB-45 and Melan-A. Recently, several other markers have been described as having excellent diagnostic sensitivity in cutaneous melanocytic lesions.

Objectives.—To compare the sensitivities of 5 melanocytic markers in renal angiomyolipoma and to study the expression patterns of these markers in the 3 different components of angiomyolipoma.

Design.—A tissue microarray of 20 renal angiomyolipomas was constructed. For each case, 3 cores containing fat, blood vessels, and smooth muscle were taken. The tissue microarray was then stained for HMB-45, Melan-A, tyrosinase, NK1-C3, and CD117.

Results.—HMB-45 was positive in 95%, Melan-A in 85%, NK1-C3 in 70%, tyrosinase in 50%, and CD117 in 40% of the cases. All (20/20) were positive for HMB-45 and Melan-A combined. These 5 markers had different sensitivities in the 3 components. HMB-45 was positive in 90%, 85%, and 80% of fat, smooth muscle, and blood vessel components, respectively; Melan-A in 70%, 60%, and 40%; NK1-C3 in 55%, 55%, and 45%; tyrosinase in 30%, 40%, and 10%; and CD117 in 20%, 40%, and 10%, respectively, of these 3 components.

Conclusions.—HMB-45 and Melan-A combined were positive in 100% of the renal angiomyolipomas. We recommend the use of these 2 markers in the workup of this entity, including those with predominantly 1 component. Other melanocytic markers are of limited use. A tissue block comprising predominantly fat or smooth muscle components should be used when performing melanocytic marker immunostain.

A gene expression signature associated with survival in metastatic melanoma

Background

Current clinical and histopathological criteria used to define the prognosis of melanoma patients are inadequate for accurate prediction of clinical outcome. We investigated whether genome screening by means of high-throughput gene microarray might provide clinically useful information on patient survival.

Methods

Forty-three tumor tissues from 38 patients with stage III and stage IV melanoma were profiled with a 17,500 element cDNA microarray. Expression data were analyzed using significance analysis of microarrays (SAM) to identify genes associated with patient survival, and supervised principal components (SPC) to determine survival prediction.

Results

SAM analysis revealed a set of 80 probes, corresponding to 70 genes, associated with survival, i.e. 45 probes characterizing longer and 35 shorter survival times, respectively. These transcripts were included in a survival prediction model designed using SPC and cross-validation which allowed identifying 30 predicting probes out of the 80 associated with survival.

Conclusion

The longer-survival group of genes included those expressed in immune cells, both innate and acquired, confirming the interplay between immunological mechanisms and the natural history of melanoma. Genes linked to immune cells were totally lacking in the poor-survival group, which was instead associated with a number of genes related to highly proliferative and invasive tumor cells.

Cutaneous melanoma

Episodic exposure of fair-skinned individuals to intense sunlight is thought to be responsible for the steadily increasing melanoma incidence worldwide over recent decades. Rarely, melanoma susceptibility is increased more than tenfold by heritable mutations in the cell cycle regulatory genes CDKN2A and CDK4. Effective treatment requires early diagnosis followed by surgical excision with adequately wide margins. Sentinel lymph node biopsy provides accurate staging, but no published results are yet available from clinical trials designed to assess the therapeutic efficacy of early complete regional node dissection in those with metastatic disease in a sentinel node. Magnetic resonance spectroscopy is one technique under investigation for non-invasive, in-situ assessment of sentinel nodes. Localised metastatic disease is best treated surgically. No postoperative adjuvant therapy is of proven value for improving overall survival, although numerous clinical trials of vaccines and cytokines are in progress. Medical therapies have contributed little to the control of established metastatic disease, but molecular pathways recently identified as being central to melanoma growth and apoptosis are under intense investigation for their potential as therapeutic targets.