Acquired Melanocytic Nevi Mimicking Acral Lentiginous Melanoma in a Patient Taking a BRAF Inhibitor

This case report describes a patient in their 60s with metastatic colon cancer who developed multiple new dark nevi within 2 months of initiating encorafenib and panitumumab therapy.

Regulatory T Cells Play an Important Role in the Prevention of Murine Melanocytic Nevi and Melanomas

Melanocytic nevi are benign proliferations of pigment cells that can occasionally develop into melanomas. There is a significant correlation between increased nevus numbers and melanoma development. Our previous reports revealed that 7,12-dimethylbenz(a)anthracene (DMBA) and 12-O-tetradecanoyl-phorbol-13-acetate (TPA) induced dysplastic nevi in C3H/HeN mice, with a potential to transform into melanomas. To understand the immune mechanisms behind this transformation, we applied increasing DMBA doses followed by TPA to the skin of C3H/HeN mice. We observed that increased doses of DMBA correlated well with increased numbers of nevi. The increased DMBA dose induced diminished immune responses and promoted the expansion of regulatory T cells (Treg) that resulted in increased IL10 and reduced IFNγ levels. Mice with increased nevus numbers had loss of p16 expression. These mice had increased migration of melanocytic cells to lymph nodes (LN) and a greater percent of LNs produced immortalized melanocytic cell lines. DMBA-induced immunosuppression was lost in CD4-knockout (KO) mice. Lymphocytes in the CD4KO mice produced less IL10 than CD8KO mice. Furthermore, CD4KO mice had significantly reduced nevus numbers and size compared with wild-type and CD8KO mice. These results suggest that Tregs play a vital role in the incidence of nevi and their progression to melanoma.Prevention Relevance: There has been little progress in developing novel strategies for preventing premalignant dysplastic nevi from becoming melanomas. In this study in mice, regulatory-T cells enhanced progression of benign nevi to malignant melanomas; and by inhibiting their activity, melanomas could be retarded. The findings identify new possibilities for melanoma prevention in high risk individuals.

Agminated melanocytic nevus status post dabrafenib therapy for metastatic melanoma

Agminated melanocytic nevus is an uncommon type of mole, characterized by a local group of macular or papular pigmented lesions, well demarcated, without a common pigmented background. This pattern has also been associated with Spitz nevi, dysplastic melanocytic nevi, and non-melanocytic lesions.We describe the onset of an acquired agminated melanocytic nevus after dabrafenib treatment. Our case highlights paradoxical MAPK activation in the setting of single-agent BRAF blockade and underscores the importance of characterizing the diverse side effects of selective BRAF inhibitors. This is the first case, to our knowledge, of agminated melanocytic nevus in association with dabrafenib.

Investigation of safety, tolerability, pharmacokinetics, and pharmacodynamics of single and multiple doses of a long-acting α-MSH analog in healthy overweight and obese subjects

MC4-NN2-0453 is a novel, long-acting, selective, melanocortin-4-receptor agonist developed for treatment of obesity. This first-human-dose, randomized, double-blind, placebo-controlled trial investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of single and multiple doses of MC4-NN2-0453 in overweight to obese but otherwise healthy subjects. The trial included a single-dose part of ascending subcutaneous 0.03-1.50 mg/kg doses in overweight to obese but otherwise healthy men, and a multiple-dose part of ascending subcutaneous 0.75-3.0 mg/day doses in obese but otherwise healthy men/women. The single-dose part included 7 cohorts of 8 subjects, randomized 6:2 to active drug/placebo; the multiple-dose part included 4 cohorts of 20 subjects, randomized 16:4 to active drug/placebo. MC4-NN2-0453 was well tolerated and raised no safety concerns except for nonserious skin-related adverse events, this along with lack of weight loss effect led to premature termination of the trial. Headache, sexual-arousal disturbance, and penile erection were also reported. Single-dose pharmacokinetics showed dose-linearity and dose-proportionality. Maximum plasma concentration was observed after 50-100 hours, which then declined with a of approximately 250 hours. Plasma concentration reached steady state after 4 weeks for 0.75 and 1.5 mg/day multiple-dose cohorts, and the was similar to single dose. There were no significant pharmacodynamic effects, including effect on body weight.

Atypical melanocytic naevi following melanotan injection

Melanotan is a synthetic analogue of alpha melanocyte stimulating hormone (a-MSH) that stimulates melanogenesis. It is sold on the internet and tanning salons as a quick 'tanning jab'. We report a patient who developed multiple new onset atypical naevi within one week of receiving two Melanotan injections. This case highlights the potential risk of Melanotan in stimulating dysplastic naevi or possibly malignant melanoma.

The TFIID subunit TAF4 regulates keratinocyte proliferation and has cell-autonomous and non-cell-autonomous tumour suppressor activity in mouse epidermis

The TAF4 subunit of transcription factor TFIID was inactivated in the basal keratinocytes of foetal and adult mouse epidermis. Loss of TAF4 in the foetal epidermis results in reduced expression of the genes required for skin barrier function, leading to early neonatal death. By contrast, TAF4 inactivation in adult epidermis leads to extensive fur loss and an aberrant hair cycle characterised by a defective anagen phase. Although the mutant epidermis contains few normal anagen-phase hair follicles, many genes expressed at this stage are strongly upregulated indicating desynchronised and inappropriate gene expression. The TAF4 mutant adult epidermis also displays interfollicular hyperplasia associated with a potent upregulation of several members of the EGF family of mitogens. Moreover, loss of TAF4 leads to malignant transformation of chemically induced papillomas and the appearance of invasive melanocytic tumours. Together, our results show that TAF4 is an important regulator of keratinocyte proliferation and has cell-autonomous and non-cell-autonomous tumour suppressor activity.

Melanocyte expression of survivin promotes development and metastasis of UV-induced melanoma in HGF-transgenic mice

We previously found the apoptosis inhibitor Survivin to be expressed in melanocytic nevi and melanoma but not in normal melanocytes. To investigate the role of Survivin in melanoma development and progression, we examined the consequences of forced Survivin expression in melanocytes in vivo. Transgenic (Tg) mouse lines (Dct-Survivin) were generated with melanocyte-specific expression of Survivin, and melanocytes grown from Dct-Survivin mice expressed Survivin. Dct-Survivin melanocytes exhibited decreased susceptibility to UV-induced apoptosis but no difference in proliferative capacity compared with melanocytes derived from non-Tg littermates. Induction of nevi in Dct-Survivin and non-Tg mice by topical application of 7,12-dimethylbenz(a)anthracene did not reveal significant differences in lesion onset (median, 10 weeks) or density (4 lesions per mouse after 15 weeks). Dct-Survivin mice were bred with melanoma-prone MH19/HGF-B6 Tg mice, and all progeny expressing either individual, neither, or both (Survivin/HGF) transgenes were UV-treated as neonates and then monitored for 43 weeks. Melanocytes in neonatal Survivin+/HGF+ mouse skin were less susceptible to UV-induced apoptosis than those from Survivin-/HGF+ mice. Onset of melanocytic tumors was earlier (median, 18 versus 24 weeks; P = 0.01, log-rank test), and overall tumor density was greater (7.7 versus 5.2 tumors per mouse; P = 0.04) in Survivin+/HGF+ compared with Survivin-/HGF+ mice. Strikingly, melanomas arising in Survivin+/HGF+ mice showed a greater tendency for lymph node (35% versus 0%; P = 0.04) and lung (53% versus 22%) metastasis and lower rates of spontaneous apoptosis than those in Survivin-/HGF+ mice. These studies show a role for Survivin in promoting both early and late events of UV-induced melanoma development in vivo.

Malignant transformation of DMBA/TPA-induced papillomas and nevi in the skin of mice selectively lacking retinoid-X-receptor alpha in epidermal keratinocytes

Retinoid-X-receptor alpha (RXRalpha), a member of the nuclear receptor (NR) superfamily, is a ligand-dependent transcriptional regulatory factor. It plays a crucial role in NR signalling through heterodimerization with some 15 NRs. We investigated the role of RXRalpha and its partners on mouse skin tumor formation and malignant progression upon topical DMBA/TPA treatment. In mutants selectively ablated for RXRalpha in keratinocytes, epidermal tumors increased in size and number, and frequently progressed to carcinomas. As keratinocyte-selective peroxisome proliferator-activated receptor gamma (PPARgamma) ablation had similar effects, RXRalpha/PPARgamma heterodimers most probably mediate epidermal tumor suppression. Keratinocyte-selective RXRalpha-null and vitamin-D-receptor null mice also exhibited more numerous dermal melanocytic growths (nevi) than control mice, but only nevi from RXRalpha mutant mice progressed to invasive human-melanoma-like tumors. Distinct RXRalpha-mediated molecular events appear therefore to be involved, in keratinocytes, in cell-autonomous suppression of epidermal tumorigenesis and malignant progression, and in non-cell-autonomous suppression of nevi formation and progression. Our study emphasizes the crucial role of keratinocytes in chemically induced epidermal and melanocytic tumorigenesis, and raises the possibility that they could play a similar role in UV-induced tumorigenesis, notably in nevi formation and progression to melanoma.

Nevos plantares múltiples posquimioterapia

The induction of multiple melanocytic nevi in children after chemotherapy has been documented in the literature. This situation apparently has more to do with the state of immunosuppression that is produced than with any specific agent used. We present the case of a 12-year-old girl who presented with multiple plantar melanocytic nevi after multidrug chemotherapy for acute lymphocytic leukemia. None of the lesions showed any alarming clinical signs. Although the degeneration of post-chemotherapy melanocytic nevi to melanoma has not been documented in any of the cases described, the presence of a high number of melanocytic nevi is an accepted risk factor for melanoma; thus, close clinical follow-up of these patients seems advisable.

Induction of eruptive benign melanocytic naevi by immune suppressive agents, including biologicals

BACKGROUND

Eruptive naevi have been described to potentially arise in immune compromised patients.

OBJECTIVES

We describe three patients with eruptive benign melanocytic naevi during a phase of immunosuppressive therapy. METHODS/DIAGNOSIS: Two patients with Crohn disease were treated with either azathioprine monotherapy or a combination of azathioprine and infliximab, when eruptive naevi arose particularly at the palms and soles. Our third patient with plaque psoriasis developed eruptive naevi during two episodes of treatment: during a course with the biological agent alefacept and during etanercept therapy.

CONCLUSIONS

We conclude that treatment with the recently available biological agents might be associated with the formation of eruptive naevi. Although positive evidence for the occurrence of malignant pigmented lesions is lacking, alertness to the development of eruptive melanocytic naevi during treatment with biological agents is indicated.

Sudden onset of Multiple nevi after administration of 6-mercaptopurine in an adult with Crohn's disease: a case report

The correlation between combined chemotherapy, including 6-mercaptopurine, and development of excessive number of melanocytic nevi in childhood has been previously reported and studied. As of yet, no such relation has been reported in adults. We recently observed a 27-year-old female patient who developed numerous benign melanocytic nevi during a 20-month period while taking 6-mercaptopurine for Crohn's disease. The appearance of many nevi was worrisome to the patient from a cosmetic and medical perspective (given the higher risk of melanoma associated with large numbers of nevi).

Hyperpigmented scar due to minocycline therapy

A 20-year-old woman presented with a heavily pigmented scar on the left lower abdomen following excision of a benign compound nevus. Reexcision showed an organizing scar with pronounced hemosiderinlike pigment deposition and no residual melanocytic lesion. Results of further histopathologic workup showed positive staining with both Perls stain for iron and Fontana-Masson stain. These findings led to further questioning of the patient, which revealed a history of minocycline therapy--information that had not been provided during her initial evaluation. Hyperpigmented scars may result from minocycline ingestion. We present a review of the literature, with particular regard to the possible mechanisms of minocycline hyperpigmentation and the differential diagnosis of hyperpigmented scars.

UV light from 290 to 325 nm, but not broad-band UVA or visible light, augments the formation of melanocytic nevi in a guinea-pig model for human nevi

We have previously described a guinea-pig model where pigmented nevi similar to human nevi can be produced by application of low-dose topical 7,12-dimethylbenzanthracene (DMBA) followed by solar-simulated light. Five groups of guinea-pigs were used to test the effect of various spectral bands of solar-simulated light on low-dose DMBA-induced melanocytic nevi. Animals were irradiated with either UVB to near UVA2 (290-325 nm), UVA, visible light, full solar spectrum or no irradiation three times per wk for 12 mo to determine the broad-band effect of nevi-inducing irradiation. There was a significant increase in nevi/animal in the UVB-treated group (mean 1.53) compared with all groups (versus UVA 0.3, p<0.001; versus visible light 0.24, p<0.001; versus full spectrum (UVB+UVA+visible) 0.68, p=0.02; versus control (nil irradiation) 0.37, p=0.01). No differences in skin thickness were found between any group (p=0.11). In conclusion, we present a report of the active waveband of melanocytic nevi induction; where UVB to near UVA2 is the likely responsible waveband. Furthermore, because there was a significant decrease in nevi/animal receiving the full solar spectrum compared with the UVB group, it is possible that broad-band UVA and or visible light may be inhibitory wavebands for nevi induction.

Topical application of dimethylbenz[a]anthracene results in the generation of multiple melanocytic nevi in C3H/HeN mice

Melanocytic nevi are a common dermatological problem for which there are few in vivo models. It has been postulated that environmental factors contribute to their development. Experiments were therefore conducted to determine whether application of dimethylbenz[a]anthracene (DMBA) to the skin of mice would result in the development of melanocytic nevi. One hundred microliters of a 0.1%, 0.5%, or 1.0% solution of DMBA was applied to the dorsal skin of C3H/HeN mice. The mice were then observed for the appearance of pigmented lesions. Histological examination revealed perifollicular accumulations of nevus cells, which were S-100-protein and HMB-45-positive, confirming their melanocytic origin. Pigmented lesions did not occur in animals treated with vehicle alone. Dose response studies revealed both greater numbers of nevi and lesions with larger diameters as the dose of DMBA was increased from 0.1% to 0.5%. In no instance was an invasive melanoma observed even after 40 weeks. The fact that melanocytic nevi can be produced by topical application of DMBA suggests that xenobiotics may play a previously unrecognized role in the development of this common benign neoplasm. Because this is one of the only animal models for melanocytic nevi, further examination of this model may facilitate identification of the molecular and biochemical mechanisms that lead to the development of pigmented nevi and the factors that promote their evolution into invasive melanomas.

Eruptive multiple lentigo-maligna-like lesions in a patient undergoing chemotherapy with an oral 5-fluorouracil prodrug for metastasizing colorectal carcinoma: a lesson for the pathogenesis of malignant melanoma?

Induction of multiple eruptive dermal and atypical melanocytic naevi has frequently been reported in children with malignant haematological diseases and chemotherapy-induced immunosuppression. This is the first report of an adult patient to develop multiple eruptive melanocytic skin lesions while undergoing chemotherapy with an oral 5-fluorouracil prodrug for metastasizing cancer. Our observation adds further evidence to the link between systemic (iatrogenic or intrinsic) immunosuppression and the induction of melanocyte proliferation and transformation.

The augmentation of melanocytic nevi in guinea pigs by solar-simulated light: an animal model for human melanocytic nevi

Strong epidemiological evidence confirms the role of sunlight in human melanoma induction. Furthermore, the frequency of melanocytic nevi is a good indicator of future development of melanoma and a short-term marker of adverse reactions to melanoma-inducing sun exposure in humans. Thus, the aim of this study was to develop and define an animal model for sunlight-induced nevi that can be used as a surrogate model for sunlight-induced melanoma. Five treatment groups of 30-40 Hartley albino guinea pigs/group were treated with topical 7,12-dimethylbenzanthracene at a dose range of 6-240 mg on the dorsum of the skin. At week 20, half of the animals in each group were given a 12-month regimen of minimal erythemal solar-simulated light, 3 times/week, increased weekly to maintain erythema. These regimes induced epidermally derived pigmented melanocytic nevi clinically and histologically similar to human nevi (junctional, compound, and dermal). S100 and HMB45 staining was also consistent with the patterns seen in human nevi. In contrast to the high-dose 7,12-dimethylbenzanthracene-treated animals (60 and 240 mg), where solar-simulated light had no effect on nevi multiplicity, those groups treated with low doses (24, 12, and 6 mg) had a significant increase in nevi multiplicity after 12 months of solar-simulated light treatment (24 mg, 0.5 nevi/animal unirradiated versus 1.4 nevi/animal irradiated, P = 0.03; 12 mg, 0.2 unirradiated versus 1.2 irradiated, P = 0.02; 6 mg, 0 unirradiated versus 1.9 irradiated, P = 0.008). UVB-induced minimal erythemal dose was unaltered after exposure to photoreactivating light, consistent with the observation of others that placental mammals lack the DNA photolyase responsible for strong photoreactivation seen in nonplacental mammals and lower metazoans. Thus, our guinea pig model has some of the essential elements required to be a robust animal model for human nevi and a surrogate model for melanoma. These nevi are augmented by solar-simulated light, are histologically similar, occupy the same level within the skin, have the same natural history as human nevi, and are produced in an animal lacking strong photoreactivation. These features are not found in any previously described small laboratory animal model.

[Eruptive melanocytic nevi after chemotherapy]

BACKGROUND

Induction of melanocytic naevi by chemotherapy in children is reported in the literature. The reason for this phenomenon is not known yet.

HISTORY AND CLINICAL FINDINGS

We present a 6-year-old girl who fell ill with acute lymphoblastic leukemia at the age of 2 years. After a combined chemotherapeutic treatment for 2 years followed by complete remission of leukemia, many (> 100) small pigmented naevi appeared over the whole body. The naevi did not show features suggestive of dysplasia.

CONCLUSIONS

Patients with excess numbers of melanocytic naevi constitute a risk group for malignant melanoma, therefore periodic skin examination is recommended.

Lack of effect of growth hormone therapy on the count and density of melanocytic naevi in children

An observation of accelerated growth of acquired melanocytic naevi (AMN) during treatment with human growth hormone (GH) raised concerns about the potential risk of melanoma in treated patients. An increased number of AMN, rather than growth rate, is associated with a higher risk for melanoma. It is unknown whether treatment with GH causes an increase in numbers of AMN. We evaluated the effect of GH treatment on the number of AMN in a cross-sectional study of 90 children with GH deficiency. AMN counts and densities in these children were compared with those found in a control group of 100 children. Factors potentially related to increased numbers of AMN, such as age, sex, skin colour, number of episodes of sunburn and duration of GH therapy were determined. Among the various factors, only the age and colour of unexposed skin area were predictive for the total number and density of AMN. No correlation was found between the AMN counts or density and the duration of GH therapy. There was no difference in AMN counts or density between the GH-deficient patient group and the control groups. We conclude that GH therapy in children is not associated with increased AMN count and density and is unlikely to potentiate the risk for melanoma in these children.

Naevocyte triggering by recombinant human growth hormone

The influence of growth hormone and insulin-like growth factor I on human melanocytes is being increasingly recognized. Clinical evidence has shown that when recombinant human growth hormone (hGH) is administered to children of short stature, the growth of melanocytic naevi is boosted. This study was conducted on 56 hGH-triggered naevi and nine similar lesions excised before or after hGH therapy for hypopituitarism and Turner's syndrome. A series of 40 naevi excised from age-matched healthy children served as controls. Atypicality of naevocytes was investigated using image analysis, AgNOR counts, immunohistochemistry (HMB-45, NKI-C3, Ki-67, anti-bcl-2-oncoprotein), and DNA flow cytometry. The data associate hGH treatment with anisokaryosis and increased AgNOR and Ki-67 counts in naevocytes. The same cells also show abnormal patterns of HMB-45 immunolabelling. These indications of naevocyte activation were not suggestive of malignant transformation. hGH-triggered melanocytomas should be added to the list of atypical melanocytic naevi. The long-term evolution of these lesions remains unknown and the potential risk of malignant transformation awaits careful evaluation.

[Induction of multiple melanocytic nevus cell nevi in 2 children with malignant hematologic systemic diseases and chemotherapy-induced immunosuppression]

Two children developed multiple melanocytic naevi after polychemotherapy administered for acute lymphoblastic leukaemia in one and for non-Hodgkin lymphoma in the other. Induction of naevi does not seem to be related to specific agents used in chemotherapy, but rather to the immunosuppression resulting from multiple-agent chemotherapy. There are reports in the literature of both intrinsically and iatrogenically immunosuppressed patients who have developed multiple melanocytic naevi.

Effect of maintenance chemotherapy in childhood on numbers of melanocytic naevi

OBJECTIVE

(a) To determine whether children given chemotherapy for haematological malignancy have significantly more melanocytic naevi than age matched children in the local population; (b) to establish whether any observed variation in naevus counts from normal is seen at the start of maintenance chemotherapy.

DESIGN

Follow up of 29 consecutive children starting maintenance chemotherapy, with parental interview and count of all melanocytic naevi > or = 2 mm on the child's skin. Assessment repeated three years later after completion of maintenance chemotherapy. Other dermatological problems identified at either visit were also recorded.

SETTING

Royal Hospital for Sick Children, Glasgow.

RESULTS

At the start of maintenance chemotherapy all children had total body counts of melanocytic naevi within the normal range established for age matched children in the local population. Three years later total body naevus counts were significantly increased, the median increase being 66 naevi per child (95% confidence interval 57 to 94). The only other problem noted in these children was relatively poor regrowth of scalp hair.

CONCLUSION

Children on maintenance chemotherapy for haematological malignancies develop an excessive number of melanocytic naevi. Excessive numbers of melanocytic naevi are the most important risk factor for melanoma in the general population. These children should have periodic skin examinations at their follow up visits, and both child and parent should be educated about clinical features of early melanoma.

Acral PUVA--induced pigmented macules

This report describes four patients with chronic psoriasiform dermatitis of the palms and soles who developed pigmented macular lesions after localized photochemotherapy (PUVA) to these areas. These lesions had varied histopathologic presentations including lentigines, atypical melanocytic proliferation and a junction nevus suggesting a wide clinico pathologic spectrum in the PUVA-induced pigmented macules.

[Acral nevi following chemotherapy]

Multiple melanocytic nevi showing an unusual accumulation on the soles of the feet were observed in an 8-year-old boy after he had received chemotherapy for acute lymphatic leukemia. This observation confirms the occurrence of chemically induced melanocytic nevi as well as their affinity for the acral sites.

Excess benign melanocytic naevi after chemotherapy for malignancy in childhood

OBJECTIVE

To see whether children who have had chemotherapy develop increased numbers of moles.

DESIGN

Blind assessment of patients having chemotherapy and subsequent comparison with the first suitable patients matched for age and sex who were attending the clinic during the same period after having completed treatment. Controls were obtained the following year by taking the first suitable patients attending a routine dermatology outpatient clinic who matched the study groups for age and sex.

SETTING

Referrals to a paediatric oncology clinic and a dermatology clinic at two city hospitals.

PATIENTS

The group receiving chemotherapy comprised all 32 patients with acute lymphatic leukaemia, lymphoma, and rhabdomyosarcoma who were attending the paediatric oncology clinic on two mornings a week during October 1987 to March 1988. The group who had completed treatment comprised 32 patients who were attending for follow up during the same period and who matched the first group for age and sex. Thirty two other patients attending the dermatology outpatient clinic with unrelated skin conditions served as controls.

END POINT

Definite increase in numbers of moles on children after a course of chemotherapy.

MEASUREMENTS AND MAIN RESULTS

Moles were counted by one observer on defined areas of the body and divided into those less than 3 mm and greater than or equal to 3 mm diameter. Patients receiving chemotherapy had a similar number of moles to the control group. By contrast patients who had completed chemotherapy had significant increases both in moles less than 3 mm and greater than or equal to 3 mm and in the total number of moles. These patients were more likely to have moles on acral sites.

CONCLUSIONS

Children with substantially increased numbers of moles (benign melanocytic naevi) after successful chemotherapy for malignancy may have an increased risk of melanoma. They should be offered prolonged surveillance and cautioned about exposure to ultraviolet light.

Evaluation of premalignant and malignant lesions during the induction of mouse melanomas

The objective of the present study was to evaluate the malignant and premalignant lesions that arise in C57BL/6 mice after treatment with 7,12-dimethylbenz(a)anthracene and croton oil. Tissues from 70 treated mice were evaluated by histological and transplantation techniques, and 17 (24%) were found to have malignant tumors. Eleven of the tumors were diagnosed as malignant melanomas, three as spindle cell sarcomas, and three as squamous cell carcinomas. The incidence of malignant melanomas (15.7%) in this group of mice was similar to that in our initial study on the induction of melanomas with 7,12-dimethylbenz(a)-anthracene and croton oil, in which two of 20 mice developed malignant melanomas. Mice that developed melanomas had been treated with croton oil for an average of 7 mo, and the mean latent period for tumor development was 11 mo. Seven of eight melanomas grew rapidly after transplantation to syngeneic C57BL/6 mice. Pigmented nevi and/or draining lymph nodes from nine of 11 mice with melanomas grew progressively after transplantation to athymic nude mice. Pooled nevi from one mouse with no apparent tumors grew into a histologically malignant melanoma after transplantation to a nude mouse. Nevi from three mice with sarcomas, one mouse with a carcinoma, and 42 tumor-free treated mice failed to grow in nude transplant recipients. Thus, only nevi from mice with either apparent or occult malignant melanomas exhibited progressive growth in nude mice. These results confirm that malignant melanomas can be induced in C57BL/6 mice at a regular, predictable rate and further indicate that this is an excellent system in which to study melanoma induction, progression, and therapy.

Guinea pig cutaneous nevi transplanted to athymic nude mice: a potential model for benign and malignant melanocytic lesions

Junctional and compound pigmented nevi, induced by 9,10-dimethyl-1,2-benzanthracene in the skin of albino guinea pigs, were transplanted as split- and full-thickness grafts to athymic nude mice. This experiment was designed as a feasibility study to establish a model in which junctional nevi could be kept outside the donor organism for prolonged periods. Different methods of securing grafts and promoting their survival were used in 19 mice. Mice died or were killed between 15 and 178 days after grafting. Histology revealed that the grafts survived in 11 mice. Nevus cells were found in six mice. The time from grafting to the observation of nevus cells did not exceed 68 days. All nevi showed slight to advanced features of degeneration and disappearance. Poor survival of the guinea pig epidermal portion of the graft and a host cellular reaction appeared to be the main reasons why nevi had a tendency to disappear from the athymic nude mouse skin.

Nevi and melanoma induced by chemical carcinogens in laboratory animals: similarities and differences with human lesions

The isolation of benzo(a)pyrene (BP) from coal tar, and the synthesis of dibenzanthracene (DBA), methylcholanthrene (MCA), and dimethylbenzanthracene (DMBA) in the 1930's, facilitated the induction of epidermal tumors in experimental animals. It was soon found that chemical carcinogens affect not only keratinocytes, but also the melanocytes (Szabo 1953). "Painting" the skin of small laboratory animals, with carcinogens, became the principal method of studying the mechanisms of chemical carcinogenesis (Yuspa et al. 1976a). Pigmented nevi and melanoma are perhaps two of the most interesting problems in dermatology, oncology and pathology. Questions related to histogenesis, classification, diagnosis, treatment and eventual prevention remain unanswered. A substantial amount of our work is used to support most of the main points regarding the development of nevi and melanoma in laboratory animals.

Phenol chemosurgery for removal of deep facial wrinkles

The derivation of the different phenol formulas for facial rejuvenation is traced. The method of action of phenol and the formula additives is discussed and an improved technique is described with which deep as well as superficial wrinkles of the face can be removed. Phenol chemosurgery is a proper alternative to the surgical face lift in properly selected patients. The potential complications of the procedure should not detract from the benefits.

Junctional and compound pigmented nevi induced by 9, 10-dimethyl-1,2-benzanthracene in skin of albino guinea pigs

Seventy albino guinea pigs were used in the experiment to investigate the influence of 9,10-dimethyl-1,2-benzanthracene on amelanotic melanocytes. A field 5 sq cm was marked on the flank of each animal. Hairs from these fields were clipped twice a week and painted for 20 consecutive weeks with 0.3 ml of 1% 9,10-dimethyl-1,2-benzanthracene in acetone. During the 1-year observation period, pigmented sports appeared in 40 animals. Biopsies were taken under local anesthesia, and sections were prepared for light and electron microscopic observations. Melanin formation of unknown mechanism took place in the epidermal melanocytes and in the melanocytes from the outer root sheath. These melanocytes also formed junctional and compound nevi; serial sections revealed various stages of pigmented nevi development. Schwann cells did not participate in the formation of nevi. Evidence is presented that 9,10-dimethyl-1,2-benzanthracene can convert amelanotic melanocytes into melanin-producing cells in the albino guinea pig skin. In addition, this system produces an animal model for the development of junctional and compound nevi.