Immunohistochemical labeling of normal melanocytes

Cutaneous Melanomas: A Single Center Experience on the Usage of Immunohistochemistry Applied for the Diagnosis

Cutaneous melanoma (cM) is the deadliest of all primary skin cancers. Its prognosis is strongly influenced by the stage at diagnosis, with early stages having a good prognosis and being potentially treatable with surgery alone; advanced stages display a much worse prognosis, with a high rate of recurrence and metastasis. For this reason, the accurate and early diagnosis of cM is crucial-misdiagnosis may have extremely dangerous consequences for the patient and drastically reduce their chances of survival. Although the histological exam remains the "gold standard" for the diagnosis of cM, a continuously increasing number of immunohistochemical markers that could help in diagnosis, prognostic characterization, and appropriate therapeutical choices are identified every day, with some of them becoming part of routine practice. This review aims to discuss and summarize all the data related to the immunohistochemical analyses that are potentially useful for the diagnosis of cM, thus rendering it easier to appropriately applicate to routine practice. We will discuss these topics, as well as the role of these molecules in the biology of cM and potential impact on diagnosis and treatment, integrating the literature data with the experience of our surgical pathology department.

Hypopigmented burn hypertrophic scar contains melanocytes that can be signaled to re-pigment by synthetic alpha-melanocyte stimulating hormone in vitro

There are limited treatments for dyschromia in burn hypertrophic scars (HTSs). Initial work in Duroc pig models showed that regions of scar that are light or dark have equal numbers of melanocytes. This study aims to confirm melanocyte presence in regions of hypo- and hyper-pigmentation in an animal model and patient samples. In a Duroc pig model, melanocyte presence was confirmed using en face staining. Patients with dyschromic HTSs had demographic, injury details, and melanin indices collected. Punch biopsies were taken of regions of hyper-, hypo-, or normally pigmented scar and skin. Biopsies were processed to obtain epidermal sheets (ESs). A subset of ESs were en face stained with melanocyte marker, S100β. Melanocytes were isolated from a different subset. Melanocytes were treated with NDP α-MSH, a pigmentation stimulator. mRNA was isolated from cells, and was used to evaluate gene expression of melanin-synthetic genes. In patient and pig scars, regions of hyper-, hypo-, and normal pigmentation had significantly different melanin indices. S100β en face staining showed that regions of hyper- and hypo-pigmentation contained the same number of melanocytes, but these cells had different dendricity/activity. Treatment of hypo-pigmented melanocytes with NDP α-MSH produced melanin by microscopy. Melanin-synthetic genes were upregulated in treated cells over controls. While traditionally it may be thought that hypopigmented regions of burn HTS display this phenotype because of the absence of pigment-producing cells, these data show that inactive melanocytes are present in these scar regions. By treating with a pigment stimulator, cells can be induced to re-pigment.

Effect of serum from healthy individuals on the growth of melanocytes in vitro following moxibustion at the "Jiudianfeng" point

Objective

To investigate the effects of serum from healthy individuals obtained following moxibustion at the “Jiudianfeng” point on melanocytes in vitro .

Methods

Ten healthy adults (five male and five female) were treated by moxibustion at the “Jiudianfeng” point for 30 minutes once daily for 3 months. The effects of treatment with serum obtained following moxibustion on melanocyte proliferation, melanin content, tyrosinase activity, cell cycle progression, and c-kit mRNA and protein expression were assessed in vitro before and after moxibustion for 1, 2, and 3 months.

Results

Exposure to sera from healthy adults following moxibustion therapy promoted melanocyte proliferation, melanin synthesis, tyrosinase activity, and c-kit mRNA and protein expression in vitro . Melanin synthesis and tyrosinase activity increased in the first 2 months following moxibustion and a synchronous decline was observed during the third month. Serum also promoted melanocyte entry into the G1 phase of the cell cycle.

Conclusions

Serum treatment following moxibustion at the “Jiudianfeng” point promoted melanocyte proliferation and melanin synthesis. Further exploration of this intriguing phenomenon is essential.

Diagnostic Immunohistochemistry in Cutaneous Neoplasia: An Update

Immunohistochemistry (IHC) is an important adjunct in the diagnosis of neoplastic skin diseases. In addition to the many established IHC markers currently in use, new markers continue to emerge, although their general acceptance and routine application requires robust validation. Here, we summarize the most well-established and commonly used biomarkers along with an array of newer ones reported in the past several decades that either demonstrate or hold high clinical promise in the field of cutaneous pathology. We also highlight recent applications of novel IHC markers in melanoma diagnosis including genetic mutation status markers [e.g. BRAF (v-raf murine sarcoma viral oncogene homolog B) and NRAS (neuroblastoma RAS viral oncogene homolog)] and an epigenetic alteration marker (e.g. 5-hydroxymethylcytosine). We specifically focus on the role of IHC in the differential diagnosis of cutaneous lesions that fall under the following categories: melanoma, epidermal tumors with an intraepidermal epitheliomatous pattern, spindle cell lesions of the dermis, small round blue cell tumors of the dermis, and cutaneous adnexal tumors. While IHC is a valuable tool in diagnostic dermatopathology, marker selection and interpretation must be highly informed by clinical context and the histologic differential diagnosis. With rapid progress in our understanding of the genetic and epigenetic mechanisms of tumorigenesis, new IHC markers will continue to emerge in the field of diagnostic dermatopathology.

Immunolocalization of tenascin-C in vitiligo

The disappearance of melanocytes because of defective adhesion is one of the accepted theories to explain vitiligo. Tenascin-C is a large, extracellular matrix glycoprotein that is thought to inhibit adhesion of melanocytes to fibronectin. The current study aimed to evaluate the pattern of tenascin-C expression in vitiligenous skin compared with normal pigmented skin by means of immunohistochemistry. The study was carried out on skin biopsies from lesional and perilesional skin of 30 patients with vitiligo and on normal skin of 10 healthy volunteers. Several histopathologic changes were observed in vitiliginous skin such as keratinocyte vacuolization, a thickened basement membrane, and dermal inflammatory changes. Tenascin-C was expressed in keratinocytes of the basal epidermal layer of normal skin biopsies at a mild intensity but it did not stain the dermis, whereas vitiligenous skin showed tenascin-C expression in most cases (93.3% ), in the papillary dermis, epidermis, and in both. Diffuse epidermal expression of tenascin-C correlated with more loss of pigment and continuous staining of tenascin-C in the papillary dermis correlated with progressive forms of vitiligo. Intense tenascin-C expression was associated with a more progressive course of the disease assessed by the vitiligo disease activity score. From this study, tenascin-C is highly expressed in the dermis, epidermis, and both of vitiligo as a secondary event for the disease. Keratinocyte is a source of tenascin-C in vitiligo, and diffuse epidermal expression of tenascin-C may induce more loss of melanocytes and melanin pigment. Dermal expression of tenascin-C in the vitiligenous lesion may be linked to the disease more than epidermal expression, because this pattern is only seen in a vitiligenous lesion and it is completely absent in normal and perilesional skin.

Clinical, pathologic, and ultrastructural studies of progressive macular hypomelanosis

BACKGROUND

Progressive macular hypomelanosis (PMH), a condition of uncertain etiology, is characterized by asymptomatic hypopigmented macules, predominantly located on the trunk. To date, the study of this disease has been sporadic and there are still no clinical diagnostic criteria. The aim of this study was to investigate the histopathologic and ultrastructural characteristics of PMH, and propose the clinical diagnostic criteria of PMH.

METHODS

The Wood's lamp and Confocal Laser Scanning Microscopy were used to observe the lesions' features. Skin biopsies were used for hematoxylin and eosin staining, melanin staining, antibodies staining of S-100 protein, tyrosinase-related protein-1(TRP-1) and tyrosinase (T311), and also for ultra-structural study. Melanocytes were isolated and cultured from the lesions.

RESULTS

Under Wood's lamp examination, the lesions of PMH showed punctiform red fluorescence. Confocal Laser Scanning Microscopy observation of the lesion showed that its "pigmented ring" around the dermal papillae was intact, but its melanin content was decreased compared with the surrounding normal skin. Ferrous sulfate staining showed that melanin content in the lesion of PMH was significantly decreased compared with the normal skin (P < 0.05). S-100 staining showed that the number of positive cells in the basal layer had no statistical significance (P > 0.05) between the lesion areas (8.25 ± 0.96) and the surrounding normal skin (8.75 ± 1.71). TRP-1 staining showed no significant difference between lesion areas (4.25 ± 0.96) and the surrounding normal skin (4.50 ± 1.29) (P > 0.05), and T311 staining also showed no difference between lesion areas (4.01 ± 0.87) and the surrounding normal skin (4.30 ± 1.05) (P > 0.05). Ultra-structural studies revealed a large reduction in the number of mature melanosome from PMH lesions. There were many membrane-bound groups in PMH lesions with normal appearance the margin, which contained a number of smaller type II-IV melanosomes, which were distributed in clusters. No degradation of melanosomes was present in the lysosomal compartments of PMH lesions. When melanocytes from the PMH lesions were cultured in vitro, the morphology of those melanocytes showed no difference compared with normal melanocytes.

CONCLUSION

As a result of the above findings, we discussed and summarized the PMH's clinical diagnostic criteria.

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.

Skin layer-specific Melan-A expression during progression of human cutaneous melanoma: implications for diagnostic applications of the marker

Melan-A is widely used in the diagnostics of human melanoma. The immunogenicity of this glycoprotein makes it a potential target in immunotherapy and several authors have suggested its potential as a prognostic factor. Up to now there has been no clear direct evidence of changes of Melan-A expression during the progression of melanoma. We have performed objective immunohistochemical assessment of the expression of Melan-A in benign naevi and melanomas at different stages of progression. Our results show a complex pattern of changes in the expression of Melan-A in melanomas depending on the location of melanoma cells within individual skin layers. The expression of the antigen during tumour progression significantly decreases for melanoma cells located in the granular/spinous layer (r=-0.94, P=0.02) and increases for the papillary layer (r=0.99, P=0.002) and reticular layer (r=0.89, P=0.04). It should also be emphasized that from the Clark II level of progression the melanomas can be detected with high sensitivity and specificity using a simple cut-off test based on the determination of Melan-A expression in tumour cells located within the papillary layer.

Immunoarchitectural characterization of a human skin model reconstructed in vitro

CONTEXT AND OBJECTIVE

Over the last few years, different models for human skin equivalent reconstructed in vitro (HSERIV) have been reported for clinical usage and applications in research for the pharmaceutical industry. Before release for routine use as human skin replacements, HSERIV models need to be tested regarding their similarity with in vivo skin, using morphological (architectural) and immunohistochemical (functional) analyses. A model for HSERIV has been developed in our hospital, and our aim here was to further characterize its immunoarchitectural features by comparing them with human skin, before it can be tested for clinical use, e.g. for severe burns or wounds, whenever ancillary methods are not indicated.

DESIGN AND SETTING

Experimental laboratory study, in the Skin Cell Culture Laboratory, School of Medical Sciences, Universidade Estadual de Campinas.

METHODS

Histological sections were stained with hematoxylin-eosin, Masson's trichrome for collagen fibers, periodic acid-Schiff reagent for basement membrane and glycogen, Weigert-Van Gieson for elastic fibers and Fontana-Masson for melanocytes. Immunohistochemistry was used to localize cytokeratins (broad spectrum of molecular weight, AE1/AE3), high molecular weight cytokeratins (34betaE12), low molecular weight cytokeratins (35betaH11), cytokeratins 7 and 20, vimentin, S-100 protein (for melanocytic and dendritic cells), CD68 (KP1, histiocytes) and CD34 (QBend, endothelium).

RESULTS

Histology revealed satisfactory similarity between HSERIV and in vivo skin. Immunohistochemical analysis on HSERIV demonstrated that the marker pattern was similar to what is generally present in human skin in vivo.

CONCLUSION

HSERIV is morphologically and functionally compatible with human skin observed in vivo.

Nipple-areolar pigmentation: histology and potential for reconstitution in breast reconstruction

The makeup of nipple-areolar skin, in terms of its melanin and melanocyte content has not previously been established. This histological information is required if pigmentation of the reconstructed nipple-areola is to be successful in post-mastectomy breast reconstruction. We describe examination of 200 parallel sections of nipple-areolar skin of 20 women using histochemical (Masson-Fontana) and immunohistochemical (Mel-5) techniques, evaluated using quantitative image analysis. The amount of melanin present per length of basement membrane was 2.14 times higher in areolar skin than breast skin. The ratio of melanocytes to keratinocytes was 1:9.7 in areolar skin vs. 1:14.7 in breast skin. We also describe a cell culture and skin construct method using autologous human serum without toxic growth promoting additives, which could be used in the clinical setting of nipple-areolar reconstruction.

The use and application of special techniques in assessing melanocytic tumours

To improve diagnostic accuracy, a number of novel techniques have been developed to assist in the evaluation of melanocytic tumours. Dematologists have begun to explore the use of new instruments, such as dermoscopy or confocal scanning laser microscopy, in their clinical assessment of pigmented lesions. They have also benefited from advances in digital photography and applied this technique to monitor patients with numerous atypical naevi. Likewise, the diagnostic armamentarium of pathologists has been enriched over the past decade. A number of new reagents have become available for immunohistochemical analysis of melanocytes in archival material, such as antibodies to tyrosinase, Melan-A/Mart-1, micropthalmia-associated transcription factor and PNL2. These markers have allowed improvements in the sensitivity and specificity in the diagnosis of melanoma and its distinction from histological mimics. However, some pitfalls in the use of various reagents have also become apparent. Most recently, molecular techniques are being explored for their potential use in the diagnosis of melanoma. In this review, various modalities are discussed with regard to their application in the evaluation of melanocytic neoplasms.

Proliferative Nodules in Congenital Melanocytic Nevi

Congenital melanocytic nevi (CMN) occur in 1% to 2% of newborns, and the risk of malignant melanoma is increased in patients with large CMN. Appearance at birth or later of a nodular or hyperpigmented area within a CMN simulates malignant melanoma and prompts biopsy. Although their clinical and pathologic features seem ominous, proliferative nodules (PNs) typically are benign and may regress, although atypical features cause greater concern. Here we report clinical and pathologic findings with outcome in 10 children who had multiple biopsies of large CMN with PNs. We reviewed 78 separate samples from the 10 patients and classified the 60 PNs according to published criteria. A subset of 30 samples containing both the CMN and a PNs was analyzed for immunohistochemical reactivity for melanocytic (S-100 protein, HMB45, melan-A), lymphocytic (CD45), cell-cycle/proliferative (Mib-1, p16, p21, p27, c-Myc), apoptotic (p53, Bax, c-kit, CD95), and anti-apoptotic (bcl-2) markers. Both CMN and PNs had similar expression of melanocytic, lymphocytic, and most cell-cycle/proliferative and apoptotic markers, including Mib-1, p16, p21, p27, c-Myc, Bax, CD95, and bcl-2. A greater proportion of PNs than CMN were reactive for p53 (67% vs. 30%, P < 0.0098) and c-kit (97% vs. 3%, P < 0.0001). p53 and p21 expression in CMN and all types of PNs were inversely correlated. When ordinary and atypical PNs were compared, the atypical PNs more frequently expressed p53, Mib-1, Bax, and bcl-2, but less frequently expressed p21. The c-kit expression in nearly all PNs and its absence in nearly all CMN is potentially useful for recognition of PN, suggests a delayed melanocytic maturation process in proliferative nodules, and may be likely indicative of their benign nature. p53 reactivity in concert with a lack of p21 up-regulation by immunohistochemistry suggests that a p53 mutation may be present in PN, although the immunohistochemical findings alone cannot exclude possible overexpression of wild-type p53. Regressive, involutional, or maturational changes were observed in sequential samples from 4 patients. No patient developed malignant melanoma or another melanocytic nevus-associated malignancy during the follow-up period. These findings underscore the similarities between PNs and the underlying CMN and suggest that maturational, proliferative, and apoptotic processes are involved in their clinical evolution.