Development of Cutaneous Amelanotic Melanoma in the Absence of a Functional Tyrosinase

Lack of characteristic pigmentation and a wide range of clinical presentations account for the diagnostic challenge associated with amelanotic malignant melanoma. Experimental studies of this important human cancer have been hampered by the lack of an appropriate animal model. We previously described a transgenic mouse line (TG‐3) that spontaneously develops pigmented cutaneous melanoma. F1 crosses were generated with TG‐3 and several albino strains, and backcrosses were then made with the albinos. In the present report, we describe the restricted development and characterization of cutaneous amelanotic melanoma in these albino transgenic backcrosses. The incidence and behavior of melanoma in these mice were monitored. A high incidence (80–100%) of spontaneous amelanotic melanoma was observed in albino transgenic mice derived from backcrosses with A, AKR, FVB, and SJL strains. The lowest incidence (30%) was obtained in BALB/c‐derived crosses. No tumors were observed in non‐transgenic mice. Immunohistochemical and western blot analyses using antibodies against three melanocyte‐specific markers of the tyrosinase family of proteins confirmed that the tumors were composed of amelanotic melanocytes. Furthermore, the presence of numerous premelanosomes observed by electron microscopy further supported the melanocytic origin of these tumors. Previous in vitro studies on human melanoma have suggested that cutaneous amelanotic melanoma was evolving from pre‐existing pigmented cutaneous melanoma. However, our results indicate that it can occur directly, as evidenced by the appearance of cutaneous amelanotic melanoma in the tyrosinase‐deficient albino mice. These mice represent a potentially valuable model for studying the mechanistic, diagnostic, and therapeutic features of this highly malignant neoplasm.     

Experimental Boron Neutron Capture Therapy for Melanoma: Systemic Delivery of Boron to Melanotic and Amelanotic Melanoma

The boron-containing melanin precursor analogue p-boronophenylalanine (BPA) has previously been shown to selectively deliver boron to pigmented murine melanomas when administered in a single intragastric dose. If boron neutron capture therapy is to become a clinically useful method of radiation therapy for human malignant melanoma, the boron carrier must be capable of delivering useful amounts of boron to remote tumor sites (metastases) and to poorly pigmented melanomas. We have now determined the ability of BPA to accumulate in several nonpigmented melanoma models including human melanoma xenografts in nude mice. The absolute amount of boron in the nonpigmented melanomas was about 50% of that observed in the pigmented counterparts but was still selectively concentrated in the tumor relative to normal tissues in amounts sufficient for effective neutron capture therapy. Single intragastric doses of BPA resulted in selective localization of boron in the amelanotic Greene melanoma carried in the anterior chamber of the rabbit eye and in a pigmented murine melanoma growing in the lungs. The ratio of the boron concentration in these tumors to the boron concentration in the immediately adjacent normal tissue was in the range of 3:1 to 4:1. These distribution studies support the proposal that boron neutron capture therapy may be useful as a regional therapy for malignant melanoma.     

Fine needle aspiration cytology in recurrent amelanotic melanoma: a case report

BACKGROUND: Amelanotic melanoma can mimic a wide variety of epithelial and nonepithelial malignant tumors. Varied cytomorphology of melanoma has been described on exfoliative and fine needle aspiration cytology (FNAC). We report a case of recurrent amelanotic melanoma to highlight its varied cytomorphologic features, which may cause diagnostic problems on cytologic and on histologic examinations. CASE: A 63-year-old male presented with nodular swellings in the right anterior chest wall, right axilla and back. A nodule in the chest had been excised 6 months earlier. Clinically, the lesion was interpreted as recurrent soft tissue sarcoma. FNAC revealed malignant cells with highly varied morphology with plasmacytoid and pleomorphic malignant cells with occasional fibrocollagenous tissue strands showing adherent neoplastic cells. A cytologic diagnosis of pleomorphic malignant tumor was suggested, and the original histologic slides were reviewed; they showed a striking alveolar pattern that vaguely resembled an alveolar rhabdomyosarcoma. However, on immunohistochemistry, the tumor cells were S-100 and melan-A positive and desmin negative. A final diagnosis of amelanotic melanoma was made. CONCLUSION: Awareness of the highly varied cytomorphology of amelanotic melanoma minimizes the diagnostic difficulty on fine needle aspiration smears. Suitable immunohistochemical markers are of great value in difficult situations.     

HMB-45 staining for cytology of primary melanoma of the vagina. A case report

BACKGROUND: Malignant melanoma in the vagina is very rare, but its diagnosis is usually easy if a melanin pigment is present. With cytodiagnosis, however, it is difficult to differentiate amelanotic melanoma or scantily pigmented melanoma from other conditions. In the present case, monoclonal antibody HMB-45, the efficacy of which has been established in histologic studies, was used in the cytodiagnosis of amelanotic melanoma in the vagina. CASE: A woman, aged 78 years, presented with a brownish, nodular tumor, diameter 3 cm, in the vagina. Scraping smears with Papanicolaou staining showed nonepithelial malignant cells without granules suggesting melanin. Smears stained with HMB-45 showed positive immunoreactivity. The diagnosis underwent histologic confirmation of amelanotic melanoma on the initial biopsy. CONCLUSION: Cytodiagnosis was made with HMB-45, which proved very effective in the differential cytodiagnosis of amelanotic melanoma and scantily pigmented melanoma, particularly because it obviated the need for tissue invasion.     

An immunoperoxidase study of S-100 protein in neoplastic cells in serous effusions. Use as a marker for melanoma

S-100 protein has been demonstrated on histologic sections in a number of neural and nonneural tissues, including a variety of neoplasms. Since pleural or peritoneal effusions are frequently the initial presentation of cancer, a study was undertaken to determine if S-100 protein in exfoliated cancer cells could be used as a marker for melanoma. Cells in 36 serous fluids obtained from 32 patients were retrospectively examined for S-100 protein by the peroxidase-antiperoxidase technique. All samples had been previously studied as Papanicolaou-stained cytology specimens, and 25 samples had been studied by transmission electron microscopy. All benign effusions were negative for S-100 protein. Malignant effusions were negative except for some that contained malignant melanoma cells: two of five pigmented melanomas and both cases of amelanotic melanoma. This study indicates that S-100 protein in malignant cells is a useful marker for malignant melanomas, especially the amelanotic type.     

Identification of Hereditary Variants of Cutaneous Melanoma

The identification of hereditary variants of cutaneous melanoma and analysis of the role of hereditary factors and syndromes predisposing to cutaneous melanoma were carried out. The involvement of individual nevus phenotypes in the development of this disease was determined. Based on a survey of recent molecular biological data and our studies, the etiological and genetic heterogeneity of cutaneous melanoma is reported. In relatives of patients with cutaneous melanoma and persons with multiple pigmented nevi, the malignant tumors proved to be differentiated in the direction of the neural crist tissues and/or derivatives of cutaneous mesenchyma. Based on the evidence obtained, the approaches have been developed to formation of risk groups for the purpose of early diagnostics of cutaneous melanoma.     

Identification of the hereditary variants of skin melanoma

The identification of hereditary variants of cutaneous melanoma and analysis of the role of hereditary factors and syndromes predisposing to cutaneous melanoma were carried out. The involvement of individual nevus phenotypes in the development of this disease was determined. Based on a survey of recent molecular biological data and our studies, the etiological and genetic heterogeneity of cutaneous melanoma is reported. In relatives of patients with cutaneous melanoma and persons with multiple pigmented nevi, the malignant tumors proved to be differentiated in the direction of the neural crist tissues and/or derivatives of cutaneous mesenchyma. Based on the evidence obtained, the approaches have been developed to formation of risk groups for the purpose of early diagnostics of cutaneous melanoma.     

Conjunctival amelanotic melanoma--a case report

Conjunctival melanoma is a relatively rare malignancy. It is presented as pigmented nodule in any area of conjunctiva, amelanotic tumors are pink with smooth appearance. The authors describe an amelanotic melanoma of the conjunctiva in an 82-year-old female patient. Cytological, histopathological and immunohistochemical studies revealed an invasive amelanotic melanoma exhibiting S-100 and MART-1 positivity. The patient undervent surgical and chemotherapy treatment and three years after the initial treatment is in the terminal stage of metastatic disease. Absence of pigmentation delayed early clinical detection and treatment. Awareness of this nonpigmented melanoma is crucial for early recognition and appropriate management.     

New variants of B16 mouse melanoma: differentiation and metastatic properties

A system of tumor transplantation has been developed to select metastatic variants of B16 in mutants of the C57BL/6J black strain of mice. The effects of transplantation into nonagouti a/a and mutant recipients on the production of melanin and on the metastatic potential of tumors were investigated. Transplantation of the pigmented B16 melanoma from a nonagouti black a/a host to a yellow mutant Ay/a recipient resulted in an achromic and metastatic variant melanoma, designated YB16. The amelanotic phenotype occurred consistently after more than ten passages through yellow mice and simultaneously with an increase in the incidence of pulmonary metastases. When YB16 was transplanted back to the nonagouti black a/a host, a second variant, MB16, characterized by its variable pigmentation, was obtained. Pigmented and/or entirely achromic tumors were observed. MB16 was dramatically more metastatic than B16 and YB16 when injected s.c. or i.v. Metastases in the lungs were pigmented and/or achromic. The properties of tumor cells derived from artificially induced metastases were investigated after s.c. and i.v. injections. Whereas the metastatic cells expressed a potent ability to generate metastases when injected s.c., no differences in the incidence of metastases, as compared to the metastatic potential of cells of parental origin, were observed after i.v. injection. In the MB16 variant, there appeared to be an inverse relationship between differentiation (production of melanins) and malignancy. Our results demonstrate that differentiation and metastatic behaviour are dependent on specific mutations in the host environment which generate a pool of tumor cells from which highly metastatic variants can be selected.     

VEGF—A和VEGF—C在皮肤恶性黑色素瘤表达的临床病理意义

目的：内皮细胞生长因子（Vascularendothelialgrowthfactor,VEGF）与恶性肿瘤转移密切相关,研究发现VEGF过度表达与恶性黑色素瘤转移有关,在本研究中通过研究VEGF在恶性黑色素瘤中的表达及与临床病理指标的相关性,为以VEGF为靶的抗转移治疗提供依据。方法：应用免疫组织化学技术检测恶性黑色素瘤中VEGF-A和VEGF-C表达,及与临床病理特点和生存状态的关系。结果：VEGF—A在皮肤恶性黑色素瘤中的阳性表达率是83．33％（30／36）,在色素痣中阳性表达率是15％（3／20）,两组间有显著性差异（P〈O．05）。VEGF—C在皮肤恶性黑色素瘤中的阳性表达率是88．9％（32／36）,在色素痣中阳性表达率是10％（2/20）,两组间有显著性差异（P〈0．01）。VEGF-A和VEGF—C表达与年龄、性别、肿瘤形态、肿瘤大小无显著关系,但与淋巴结转移和封闭血管环形成有关,VEGF-A和VEGF—C阳性病例淋巴结转移率和封闭血管环出现率显著高于VEGF-A和VEGF-C阴性病例。有统计学意义。对VEGF-A和VEGF-C表达与恶性黑色素瘤生存状态的关系分析显示,VEGF-A和VEGF-C表达阴性的病例的生存期和生存率均显著高于VEGF-A和VEGF-C表达阴性的病例,有统计学意义。结论：VEGF-A和VEGF-C表达与恶性黑色素瘤的淋巴结转移、血管形成和生存期相关,这两种蛋白过度表达反映黑色素瘤处于进展状态和预后差,可以作为黑色素瘤诊断、预后和复发预测的指标和靶向治疗的靶蛋白。     

Evaluation of tyrosinase minigene co-injection as a marker for genetic manipulations in transgenic mice.

The utility of tyrosinase minigene co-injection was evaluated as a visual marker for the generation and breeding of transgenic mice. In an evaluation of 39 transgenic founder animals and 44 transgenic lines five phenotypic patterns of pigmentation were consistently observed, including albino, dark, light, mottled and himalayan. In these studies co-injection of the tyrosinase minigene along with the transgene of interest (TOI) resulted in genomic integration of the two transgenes in 95% of the F0 generation. Co-segregation of transgenes occurred in 94% of doubly transgenic mice in the F1 generation, without dissociation in subsequent generations. All pigmented phenotypes proved useful for distinguishing homozygous from heterozygous F2 animals via backcross trials, while the light, mottled and himalayan phenotypes proved useful in visually discriminating between homozygous and heterozygous F2 animals. In addition, the light, mottled and himalayan phenotypes proved useful in determining segregation patterns of transgenes in the progeny of crosses between separate transgenic lines. Moreover, there appears to be a correlation between intensity of pigmentation and degree of expression of the co-injected TOI. These studies confirm that tyrosinase co-injection is a useful adjunct in transgenic mouse studies and can serve to reduce routine genetic validation of transgenic lines.     

Anti-melanoma monoclonal antibody HMB45 identifies an oncofetal glycoconjugate associated with immature melanosomes.

The anti-melanoma monoclonal antibody HMB45 is widely used in diagnostic pathology owing to its great specificity and sensitivity in identifying pigmented tumors such as malignant melanoma. However, little is known regarding the nature of the antigen(s) recognized by this antibody. In the observations reported here, the HMB45-defined antigen was identified in another pigmented tissue, the retinal pigment epithelium (RPE). A series of immunocytochemical studies demonstrated transient reactivity of the prenatal and infantile human RPE with antibody HMB45; adult RPE is non-reactive with the antibody. By immunoelectron microscopy, the antibody was demonstrated to react with immature melanosomes. Pre-treatment of deparaffinized tissue sections with neuraminidase completely eliminated HMB45 immunoreactivity, suggesting that the antigen(s) recognized is a sialated glycoconjugate. Mannosidase or N-acetylglucosaminidase pre-treatment had no effect on immunoreactivity. Thus, HMB45 may identify an oncofetal antigen present in cutaneous melanocytes, RPE, and melanoma cells, and changes in immunoreactivity with maturation or malignant transformation may be a function of post-translational modification.     

Transgenic mouse models for tumors of melanocytes and retinal pigment epithelium

Cutaneous and ocular melanomas are due to malignant transformation of neural crest-derived melanocytes. The rising incidence of this tumor in humans has stimulated experiments to devise suitable mouse models. In the past years, transgenic mouse lines have been generated using different oncogenes - Ha-ras, SV40 T antigen (Tag), ret - which develop benign lesions of melanocytes, melanoma, and/or eye tumors. Pigment cell tumors in humans, although rather rare, can also develop from the retinal pigment epithelium (RPE), a cell layer of neuroectodermal origin. We, therefore, established transgenic models for this ocular tumor. Regulated by the promoter of tyrosinase-related protein-1 (TRP-1), two oncogenes, ret and SV40 Tag, were targeted to the developing RPE in transgenic mice. The TRP-1/ret transgenic mice displayed microphthalmia and benign tumors of the RPE. Expression of SV40 T antigen (TRP-1/Tag) led to malignant tumors, which were invasive and metastasized to inguinal lymph node and spleen.     

Development of early melanocytic lesions in transgenic mice predisposed to melanoma

We have previously described a line of transgenic mice (TG3) that spontaneously develops heritable malignant melanoma. Histological analysis of these animals during the first postnatal month is described here. In the TG3 line, the number of melanocytes is increased at all anatomical sites to which neural-crest-derived melanocytes normally migrate. Clonal expansion and morphological changes of these melanocytes can be detected as early as postnatal day (PND) 15. By PND 30, cells morphologically indistinguishable from the tumor cells of adult transgenic mice were detected in the ear, eye lid and perianal region. These cells are believed to be the precursors of the primary tumors in adult mice. The stepwise development of melanoma in the TG3 line is similar to the stepwise development of melanoma in humans.     

The ret oncogene can induce melanogenesis and melanocyte development in Wv/Wv mice.

We recently reported the establishment of transgenic mouse lines carrying the mouse metallothionein/ret fusion gene in which severe melanosis and melanocytic tumors developed. In the present study, we demonstrate that a significant number of pigmented hairs developed in Wv/Wv mice crossed to one of the transgenic mouse lines. The pigmented hair of Wv/Wv mice carrying the ret oncogene did not lose color during aging and reappeared after shaving, indicating that the melanocytes in the hair follicle function. The melanocytic tumors also developed in these mice, although the incidence was lower than that in the wild transgenic mice. Furthermore, the neutral tube culture of mouse embryos indicated that neural crest cells of the transgenic mice gave rise to a cell population that autonomously produced melanin even in the absence of melanocyte stimulating hormone. These results strongly suggested that the introduced ret oncogene could compensate for the defect of c-kit in Wv mice during both embryogenesis and postnatal life and induce a high level of melanin synthesis in the process of melanocyte development.     

Vitiligo-related pigment cell differentiation antigens are expressed on malignant melanoma cells following phenotypic reversion induced by contact inhibitory factor

Most vitiligo sera contain antibodies to surface antigens on pigmented human melanocytes but not to human or mouse amelanotic melanoma cells. A density-dependent line of hamster amelanotic melanocytic cells (FF) produces a diffusible factor (CIF) which restores contact inhibition of growth as well as several other normal phenotypic characteristics to hamster, murine, and human melanoma cells. The ability of CIF to induce the expression of a phenotypic characteristic of pigmented human melanocytic cells, i.e., the vitiligo-related surface antigens, on hamster and mouse amelanotic melanoma cells was investigated. Vitiligo and normal sera were reacted with CIF-treated and untreated hamster and mouse amelanotic melanoma cells for both indirect-immunofluorescence assays and ELISA. Immunofluorescence testing showed that about 80% of hamster and mouse melanoma cells had pigment-cell antigens (in the absence of pigmentation) in a granular surface pattern after, but not prior to, CIF-induced morphologic reversion and confluent growth. Less than 5% of the control hamster and mouse melanoma cells expressed such antigens at confluence. These results were confirmed by ELISA. Metabolic-labeling studies with 35S-methionine showed that the vitiligo antigens were synthesized by the CIF-treated melanoma cells. The slowing of melanoma cell proliferation in isoleucine-deficient medium failed to elicit the expression of vitiligo antigens. Since antigen appearance following phenotypic reversion occurred without pigment induction, it is concluded that vitiligo-related surface antigens and pigmentation are distinct aspects of a differentiated function which may be non-coordinately expressed. The expression of pigment-cell differentiation antigens on amelanotic melanoma cells is an additional feature of the pleiotypic trans-species response to CIF.     

Comparison of mercury levels in various tissues of albino and pigmented mice treated with two different brands of mercury skin-lightening creams

The use of mercury containing skin-lightening creams are becoming increasingly popular among dark-skinned women. The long-term use of certain brands may cause serious health effects over the years. In the present study, we investigated the dermal absorption of mercury and its accumulation in the tissues of albino and pigmented mice treated with two brands of mercury containing skin-lightening creams for a period of one months at different intervals. The mean +/- SD of mercury in the selected brands were: (1) Fair & Lovely (0.304 +/- 0.316 microg/g); and (2) Rose (77513.0 +/- 71063.0 microg/g). Mercury levels were measured in a total of 133 and 144 liver, kidney and brain tissue samples of albino and pigmented mice respectively by the Atomic Absorption Spectrophotometer coupled to Vapour Generator Accessory. In both strains, we found that the mercury concentration in the tissues of mice treated with Rose skin-lightening cream samples was significantly higher than those treated with Fair & Lovely skin lightening cream. Looking at the mercury concentration in the tissue samples with respect to the application of skin lightening creams at different intervals, the highest mercury concentrations were found in the tissues of albino and pigmented mice treated three times a day. On the other hand, the lowest mercury concentrations were found in the tissues of mice treated once a week. Despite the brand of skin-lightening cream that was applied, the study indicated that mercury was readily absorbed through the skin of both albino and pigmented mice as evidenced with its accumulation in the brain, kidney and liver tissues where the kidney had the highest mercury content and brain had the lowest (it P < 0.0001). Significant differences in the mercury levels were observed between the albino and pigmented mice. This emphasizes the protective role of melanin against mercury toxicity. Results of this study stresses the potential harm of these mercury containing skin-lightening creams regardless of their mercury contents especially for women who apply these creams frequently or for extended periods. Permanent nephrological or/and neurological deficits may occur if the damage is severe and diagnosis and treatment are delayed.     

Expression of Tyrosinase Gene in Transgenic Albino Mice: The Heritable Patterned Coat Colors

To elucidate the regulatory mechanism for tyrosinase gene expression in vivo, we microinjected a mouse tyrosinase minigene, mg-Qrs-J, into the fertilized eggs of BALB/c albino mice. As a result, we obtained six pigmented founder mice that exhibited non-standard coat color variations as well as the wild-type phenotype. These founder mice were subsequently crossed with BALB/c albino mice to establish the transgenic lines. As a consequence, two primary lines and five sublines have been obtained from four of the six founder mice. We found that not only uniformly pigmented phenotypes but also patterned phenotypes were inherited by their descendants. The possible underlying mechanism of the patterned phenotypes is discussed.