Merkel cell hyperplasia in hypertrophic varieties of actinic keratoses

Hyperplasia and dysplasia of the epidermal neuroendocrine cells (i.e., Merkel cells, MC) have been suggested in lesional skin of actinic keratosis and chronic radiation dermatitis. Because several histological types of actinic keratosis exist, we investigated the occurrence of such MC hyperplasia according to each of the histological patterns. Using an immunoperoxidase technique and the cytokeratin monoclonal antibody CAM 5.2, we counted 0.02 CAM 5.2 + cells (i.e., MC)/mm epidermis in normal-appearing perilesional skin; 0.05 MC/mm epidermis in nonhypertrophic actinic keratoses and 4.09 MC/mm epidermis in hypertrophic actinic keratoses. This number was as high as 14.40 MC/mm epidermis when hypertrophic actinic keratoses showed club-like epithelial proliferations. In contrast to normal epidermis, where MC were found isolated within the basal cell layer, MC clustered in these club-like epithelial proliferations as they did in the normal parakeratotic zone of the rabbit lip epithelium. The significance of this selective MC hyperplasia is discussed.     

Label-retaining cells in human embryonic and fetal epidermis

Human embryonic and fetal epidermis was examined and labeling indices (LIs) for basal, intermediate, and periderm cells were determined. The LI for fetal basal cells was 8-11% and the LI for fetal intermediate cells was 7.5-9%. The total fetal epidermal LI was 16-20%, which equaled the basal LI for embryonic epidermis. After 21 days in organ culture, only basal cells in the fetal epidermis labeled with tritiated thymidine, while both basal and intermediate cells in the embryonic epidermis labeled and the total LI for fetal and embryonic epidermal cells was the same as the adult epidermal LI (7%). The LI for periderm decreased with increasing estimated gestational age (EGA) from 9.5% at 49 days EGA to 0.4% at 85 days EGA. A subpopulation of epithelial cells that retained tritiated thymidine label and that have some of the attributes associated with stem cells has been previously demonstrated in rodents. In order to examine human embryonic and fetal epidermis for the presence of such cells, epidermis from various gestational ages were labeled and grown in organ culture for 21 days. The mean percent label-retaining cells (LRCs) for embryonic and fetal epidermis was determined. Approximately 4% of the embryonic and 2% of the fetal epidermal cells retained label for 21 days in organ culture. Embryonic LRCs were found in the basal and suprabasal layers, but fetal LRCs were found only in the basal layer. The presence of LRCs in human embryonic and fetal epidermis suggests that epithelial cell proliferation in these tissues may be regulated via a stem cell pattern of proliferation.     

Aneuploidy in actinic keratosis and Bowen's disease—increased risk for invasive squamous cell carcinoma?

Summary The value of DNA single cell cytometry for the detection of aneuploidy was assessed in 100 specimens of actinic keratoses and 39 specimens of Bowen's disease. Ten seborrhoeic keratoses and 10 samples of normal epidermis served as negative control groups. Monolayer smears, prepared from formalin-fixed, paraffin-embedded tissues, were Feulgen-stained and used for interactive DNA-cytometry. In each specimen, the DNA content of 150 randomly chosen squamous epithelial cells was measured, using a TV-image analysis system (TAS-plus, Leica, Germany). Aneuploidy was diagnosed if at least three nuclei with a DNA content above 5c (5cEE≥3) were found. The aneuploidy rate in actinic keratosis was 69% (69 of 100) and in Bowen's disease was 95% (37 of 39). Another 20 specimens of actinic keratoses and the remaining two specimens of Bowen's disease were diagnosed as suspicious for aneuploidy (0≤5cEE≤3). The 20 specimens of seborrhoeic keratoses nd normal epidermis did not show any nuclei above the 5c level, and were classified as non-aneuploid. This indicates a sensitivity of 76% (106 of 139) and a specificity of 100% (20 of 20). The frequent occurrence of aneuploidy in actinic keratoses and Bowen's disease underlines the character of the lesions as epidermal carcinomas in situ, but does not explain the long-term low incidence of invasive growth.     

Cytochemical expression of epidermal peroxidase and cytochrome oxidase activities in pathological skin conditions of man

Summary The cytochemical expression of epidermal peroxidase and cytochrome oxidase activity was recently well documented in normal human skin.We report here its expression in basal and squamous cell carcinomas, actinic keratoses, psoriasis, allergic contact dermatitis, seborrheic keratoses, and autosomal dominant ichthyosis vulgaris. The two enzyme activities were evaluated using the diaminobenzidine method. If present, the two enzymes were always localized in the same organelles as in normal epidermis endogenous peroxidase in the nuclear envelope and endoplasmic reticulum, and cytochrome oxidase in mitochondria. In basal and squamous carcinomas, actinic keratoses and psoriasis, the keratinocytes lost their peroxidase activity, but maintained their cytochrome oxidase activity. In seborrheic keratoses, allergic contact dermatitis and ichthyosis vulgaris, the cytochrome oxidase activity was greatly reduced or abolished in keratinocytes, Langerhans' cells, and melanocytes, whereas the peroxidase activity was present as in normal epidermis. These results indicate that the two peroxidatic enzymes studied are not interrelated and alternatively suppressed by different cellular dysfunctions.A part of this work was presented at the combined 12th SCUR Annual Meeting and 6th International Dermatopathology Colloqium, April 1985, Florence, Italy     

Prostaglandin and DNA synthesis in human skin: possible relationship to ultraviolet light effects.

The effect of prostaglandin E2 (PGE2) on DNA synthesis in human skin was evaluated. PGE2 (1 mug) was infected intradermally into normal buttock skin of 15 volunteers followed by tritiated thymidine for autoradiographic quantitation of DNA synthesizing cells. Controls of normal saline, histamine (50 mug), and lower doses of PGE2 were also injected into 8 of the volunteers. Forty-eight hours after injection of 1 mug and 0.1 mug PGE2 there was a 264% and 62% increase, respectively, in the number of DNA synthesizing epidermal cells/high-power field as compared to saline controls. These differences were statistically significant (p smaller than 0.01). Histamine (50 mug) produced a statistically significant 36% higher labeling index compared to its saline controls (p smaller than 0.05). Many types of skin injury, including ultraviolet light (UVL) irradiation, produce an increase in the number of DNA synthesizing cells about 48 hr after the stimulus. Our findings suggest that PGE, a putative mediator of UVL-induced inflammation, may be one of the chemical mediators for the UVL-induced increase in DNA synthesizing cells. Histamine may also contribute to the increase in DNA synthesizing cells following UVL-induced inflammation.     

Actinic Keratosis

Actinic keratoses are hyperkeratotic skin lesions that represent focal abnormal proliferation of epidermal keratinocytes. Some actinic keratoses evolve into squamous cell carcinoma of the skin, while others resolve spontaneously. The conversion rate of actinic keratosis to squamous cell carcinoma is not accurately known, but appears to be in the range of 0.25 to 1% per year. Although there is a low rate of conversion of actinic keratoses to squamous cell carcinoma, 60% of squamous cell carcinomas of the skin probably arise from actinic keratoses. The main cause of actinic keratoses in otherwise healthy Caucasians appears to be the sun. Therapy for actinic keratoses begins with prevention which starts with sun avoidance and physical protection. Sunprotection with sunscreens actually slows the return of actinic keratoses in patients already getting actinic keratoses. Interestingly, a few studies are available that demonstrate that a high fat diet is associated with the production of more actinic keratoses than is a low fat diet. One of the mainstays of therapy has been local destruction of the actinic keratoses with cryotherapy, and curettage and electrodesiccation. A new addition to this group of therapies to treat individual actinic keratoses is photodynamic therapy with topical aminolevulinic acid and light. In patients who have numerous actinic keratoses in an area of severely sun damaged skin, therapies which are applied to the whole actinic keratosis area are used. The goal of treating such an area of skin is to treat all of the early as well as the numerous clinically evident actinic keratoses at the same time. The classical approaches for treating areas of photodamaged skin without treating actinic keratoses individually include: the use of topically applied fluorouracil cream, dermabrasion, and cutaneous peels with various agents like trichloroacetic acid. Both topically as well as orally administered retinoids have been used to treat actinic keratoses but retinoids alone are probably not an optimal monotherapy. Photodynamic therapy with topical aminolevulinic acid and light is a new therapy for actinic keratoses. Aminolevulinic acid is a precursor of protoporphyrin IX (PpIX) which is synthesized in the actinic keratosis when it is treated with aminolevulinic acid, and the PpIX photosensitizes the actinic keratosis so that light exposure can lead to its destruction. Photodynamic therapy with topical aminolevulinic acid is approved in the US to treat multiple individual actinic keratoses on the face and scalp and has similar cure rates to those reported for cryotherapy and fluorouracil therapy.     

A new way to evaluate the germinative compartment in human epidermis, using [3H]thymidine incorporation and immunoperoxidase staining of 67 K polypeptide

We have used tritiated thymidine (3HT) labelling and immunoperoxidase staining of 67 K polypeptide in human epidermis to study normal skin before and after irritation induced by application of croton oil (20% and 50% in olive oil). By this double labelling method, it was possible to identify, on the same skin section, DNA-synthesizing nuclei and epidermal cells which contained 67 K polypeptide. Our results clearly indicate that the germinative compartment of normal epidermis is a mixed population comprising basal and adjacent suprabasal cells; as a rule, absence of expression of 67 K polypeptide, which characterizes all basal cells, could not be regarded as a good marker to distinguish the germinative from the differentiating compartments. In mild primary irritation, the ratio of 3HT-labelled undifferentiated cells to keratinizing ones was similar to that observed in normal epidermis. In severe irritation, this homeostatic process was altered, as 3HT-labelled cells were mainly 67 K negative.     

皮肤鳞状细胞癌和光线性角化病的免疫组化研究

目的探讨光线性角化病[AK]的性质以及其与鳞状细胞癌(SCC)的关系。方法用免疫组化的方法研究了桥粒芯糖蛋白1(D sg1)和E-钙黏着蛋白(Ecad)在鳞状细胞癌和光线性角化病中的表达。结果与正常人皮肤相比桥粒芯糖蛋白1和E-钙黏着蛋白在光线性角化病中的表达减弱,在鳞状细胞癌中的表达显著减弱或完全消失,但两者在角化不良细胞处的表达非常相似。结论光线性角化病应及早治疗以阻止其发展。     

A new surgical approach for the treatment of severe epithelial skin sun-induced damage

BACKGROUND: Cutaneous photoageing is a complex biological process affecting all layers of the skin. Skin damage resulting from intrinsic ageing and extrinsic photoageing may trigger skin cancer. In patients with advanced photoageing and/or diffuse actinic damage, local therapy is often inadequate and the possibility of combined therapy needs to be assessed. SUBJECTS: Here we report three cases of patients over 75 years of age with advanced diffuse epithelial skin damage of photoexposed areas consisting of several superficial actinic keratoses, ipermelanotic lesions and multiple skin cancers. METHODS: Neoplastic lesions and damaged skin were removed by superficial erbium laser ablation and the epidermis reconstructed with autologous epidermal sheets expanded in vitro from healthy cells obtained from unexposed areas of the body. RESULTS: Our initial studies show that this procedure is very effective in the short term for treating and preventing the UV-induced skin cancer and precancerous lesions, and also suggest good long-term control of the disease with very interesting aesthetic results.     

Stereotyped distribution of proliferating keratinocytes in disorders affecting the epidermis

We used the technique of autoradiography after incorporation of tritiated thymidine (3H-TdR) to evaluate keratinocyte proliferation in basal, epibasal, and other epidermal layers in 30 diseases affecting the epidermis. The number and proportion of 3H-TdR-labeled keratinocytes were counted in the different layers of the epidermis. Significant correlations were found between the proliferative indices of the different epidermal layers. Such links indicate that the epidermis responds in a rather stereotyped way to various pathological conditions. There exists some regulation in the distribution, number, and proportion of 3H-TdR-labeled keratinocytes in the various layers of the epidermis.     

The proliferation of epidermal cells in mouse ear organ culture

Summary Mouse ear fragments were cultured for up to 1 day in a chemically defined fluid medium and for 2–3 days in a solid Agar medium.Within 24 h of incubation, the epidermal cells were found to migrate towards the cut edges, a process which led to an epithelialization of the denuded surface. Concomitantly, the epidermal cell proliferation was enhanced: an entry of increasing numbers of interfollicular cells into S phase occurred after 7–10 h of incubation and was maximal around the 20th h. Correspondingly, the mitotic rate rose after 20 h. During an incubation period of 48–72 h in solid medium, the mitotic activity of the proliferating tissues in mouse ear skin continued, and the interfollicular epidermis in the proximity of the cut edges became hyperplastic. Thus, mouse ear epidermis kept in this organ culture seems to resemble a wounded epidermis in vivo.Epidermal cell proliferation was studied by determining (a) the mitotic rate and (b) the incorporation of tritiated thymidine by means of liquid scintillation spectrometry and autoradiography. Various factors affecting the incorporaton of tritiated thymidine were investigated, and it was concluded that liquid scintillation spectrometry proves to be a rapid and suitable method for determining the effects of both growth-promoting and growth-inhibiting agents on epidermal cell proliferation.     

The epidermis in thyroid disease*

Epidermal dimensions, replication and anabolic activity have been studied in thirteen patients with thyrotoxicosis and seven patients with hypothyroidism. Epidermal thickness and rete pattern were signifieantly reduced in hypothyroidism. The rates of epidermal cell division and anabolic aetivity in the epidermis were estimated by measuring the rates of incorporation of tritiated precursor compounds and were found to be increased in thyrotoxicosis. The mean autoradiographic labelling indices after the intracutaneous injection of tritiated thymidine were 9.1% in thyrotoxic patients and 4.3% in the hypothyroid group. None of the changes observed could be correlated accurately with the degree of thyroid gland activity, but increased thyroid activity was reflected in the epidermal changes better than decreased thyroid activity.     

Effect of lipid solvents on protein, DNA, and collagen synthesis in human skin: an electron microscopic autoradiographic study.

The effect of acetone and kerosene on the synthesis of protein, DNA, and collagen was studied by electron microscopic autoradiography using [3H]leucine, [3H]thymidine, and [3H]proline as tracers in human skin. Quantitative analyses following concomitant administration of tritiated leucine and acetone or kerosene demonstrated, at 90 min, a marked decrease in silver grains as compared to control or nonexposed areas. Incorporation of tritiated thymidine is moderately stimulated only by acetone, whereas radioactive proline distribution is not significantly affected. Electron microscopic autoradiograms revealed that tritiated leucine is distributed over all epidermal cells, mostly in the stratum spinosum of control epidermis; a marked decrease of silver grains from [3H]leucine followed both lipid solvent exposures. The autoradiographic reaction is specifically located over cytoplasmic organelles, such as polysomes, endoplasmic reticulum, and especially tonofilaments. Tritiated thymidine resulted in silver grains mostly over nuclear chromatin and these were moderatly increased after acetone application, whereas the incorporation of radioactive proline in the fibroblasts and collagen fibrils were not significantly influenced. These investigations indicate a dissociated effect of lipid solvents on protein, DNA, and collagen synthesis in human skin.     

Hair follicle kinetics in psoriasis

The rate of epidermal cell production has been measured in the various parts of scalp hair follicles in patients with psoriasis of the scalp, and in controls with normal scalp skin. An in vitro technique was used in which thin tissue slices were exposed to tritiated thymidine enabling cells about to divide to become autoradiographically labelled. Biopsies from thirteen patients with psoriasis and nine controls were examined in this way. The labelling indices of the interfollicular epidermis was 27-5% in the psoriatics and 9-5% in the controls. The upper part of the external root sheath had a labelling index of 28% in the psoriatic group compared to 13-9% for the controls. The labelling indices of the sebaceous glands, matrices and external root sheaths were very similar in the two groups. The findings support the hypothesis for a dermal stimulating influence causing the increased epidermopoiesis seen in psoriasis.     

Actinic keratoses--sequelae of long-term PUVA therapy

Multiple actinic keratoses occurred on skin regions that were not exposed to the sun in one (0.15%) of 672 psoriasis patients receiving long term PUVA treatment after receiving a cumulative UVA dose of 883 J/cm2. Apart from skin type II, no risk factors were found. Besides clinical signs of chronic, light-induced skin damage, there were minor indications of epidermal dystrophy. Acantholysis was abnormally common in the regions affected by actinic keratosis.     

Evaluation of the therapeutic results of actinic keratosis treated with topical 5% fluorouracil by reflectance confocal laser microscopy: preliminary study

Topical treatment for actinic keratosis with 5% fluorouracil has a recurrence rate of 54% in 12 months of follow-up. This study analyzed thirteen actinic keratoses on the upper limbs through confocal microscopy, at the time of clinical diagnosis and after 4 weeks of treatment with fluorouracil. After the treatment was established and evidence of clinical cure was achieved, in two of the nine actinic keratoses, confocal microscopy enabled visualization of focal areas of atypical honeycomb pattern in the epidermis indicating therapeutic failure. Preliminary data suggest the use of confocal microscopy as a tool for diagnosis and therapeutic control of actinic keratosis.     

Clonal heterogeneity in curetted human epidermal cancers and precancers analysed by flow cytometry and compared with histology

DNA frequency distributions analysed by single nuclei flow cytometry were studied in sixty-five curetted human epidermal tumours, i.e. five actinic keratoses (AK), seven Bowen's diseases (BO), nine squamous cell carcinomas (SCC), forty-three basal cell carcinomas (BCC) and one baso-squamous carcinoma (BSC). Seventy-five per cent (16/21) of the samples with squamous cell differentiation (AK, BO and SCC) showed features suggestive of more than one stem cell population, against 24% of the pure BCC samples (11/43). The DNA indices for the tumours, i.e. the ratio between the DNA content of the tumour stem cell line G1 cells and normal epidermis G1 cells were calculated. For BCC and SCC a preponderance was found for near-diploid and near-tetraploid cell clones. The precancerous lesions contained clones with more broadly scattered DNA indices. The fractions of cells in S and G2M and S + G2M phases were calculated for the samples with only one detectable stem cell population. For the squamous cell tumours and the nodular (but not the superficial) BCC, these fractions were significantly different from the unaffected skin of patients with multiple epidermal cancers. The usefulness of cell cycle fraction determinations for curetted tumours is discussed.     

Gamma glutamyl transpeptidase expression in foetal skin, inflammatory dermatoses and cutaneous neoplasia

Gamma glutamyl transpeptidase (GGT) is an enzyme expressed by some epithelial neoplasms but not normal interfollicular epidermis. In order to examine the relationship between malignant change and de-differentiation we studied histochemically the expression of GGT in human foetal skin, various inflammatory dermatoses and epidermal neoplasms. In foetal skin GGT was detectable after 7 weeks' gestation, reached a maximum at 11 weeks and was undetectable by 24 weeks. It was expressed strongly by squamous cell carcinoma and focally in Bowen's disease and actinic keratoses. There was no GGT expression in basal cell carcinoma or most benign skin tumours, but keratoacanthomas were weakly positive. Keratinocytes in the vicinity of malignant melanocytes also expressed GGT. This study suggests that GGT expression, while not a simple marker of malignancy, may represent reversion to a less differentiated or 'foetal' phenotype.     

Die aktinische Keratose

Actinic keratoses are defined as proliferation of cytologically atypical keratinocytes in the zone of epidermal-dermal junction in photodamaged skin. In the northern hemisphere the prevalence of actinic keratoses ranges depending on different epidemiological studies from 11% to 25% for people aged 40 or older. The main cause of actinic keratoses is exposure to UVB radiation in sunlight. UVB radiation induces mutations in the telomerase gene and in the tumor suppressor gene p53, which can also be detected in invasive squamous cell carcinoma. The only histological parameter to distinguish between actinic keratoses and SCC is the level of invasiveness. The risk for actinic keratoses to develop into SCC is about 16% over 10 years. For this reason and because of the high prevalence of actinic keratoses, it has been suggested to replace the term "actinic keratosis" with "intraepidermal squamous cell carcinoma" to better characterize the lesion. In the following review recent aspects of pathogenesis and therapy of actinic keratoses are discussed.