Peter J. Heenan

High frequency of BRAF mutations in nevi.

To evaluate the timing of mutations in BRAF (v-raf murine sarcoma viral oncogene homolog B1) during melanocytic neoplasia, we carried out mutation analysis on microdissected melanoma and nevi samples. We observed mutations resulting in the V599E amino-acid substitution in 41 of 60 (68%) melanoma metastases, 4 of 5 (80%) primary melanomas and, unexpectedly, in 63 of 77 (82%) nevi. These data suggest that mutational activation of the RAS/RAF/MAPK pathway in nevi is a critical step in the initiation of melanocytic neoplasia but alone is insufficient for melanoma tumorigenesis.

Benign melanocytic lesions: Risk markers or precursors of cutaneous melanoma?

BACKGROUND The role of benign melanocytic lesions as precursors and not only as risk markers for the development of cutaneous melanoma is controversial. OBJECTIVE The purpose of the study was to assess the frequency of the histologic association of benign melanocytic lesions with cutaneous melanoma of a maximum thickness of 1.00 mm. The possibility that the spatial association of benign lesions with melanoma may be coincidental was also investigated. METHODS The study subjects representing 289 cases of cutaneous melanoma of maximum thickness 1.00 mm (or less) were examined histologically for the presence of an associated benign melanocytic lesion(s), including lentiginous melanocytic proliferation; junctional, compound, or intradermal nevus; dysplastic nevus; and congenital nevus contiguous with or adjacent to the melanoma. The effects of age, tumor thickness, level of invasion, histologic type, and anatomic site on the association of benign melanocytic lesions with melanoma were assessed. In the control subjects 40 basal cell carcinomas and 38 compound nevi (not dysplastic) randomly chosen and matched for age (+/- 1 year) and site (head/neck, trunk, upper and lower limbs) with a melanoma case were examined to assess the proportion of these cases associated with benign lesions compared with the matched melanoma cases. RESULTS A nevus was associated with melanoma in 51% of cases (n = 147). Of these, 82 (56%) were dysplastic nevi, 61 (41%) were common acquired nevi, and 4 (3%) were congenital nevi. Lentiginous melanocytic proliferation was present in the epidermis adjacent to 219 melanomas (75%) and in 44% of these cases (n = 97) a coexisting nevus was also present. CONCLUSION The results of this study lend further support to the concept of common acquired nevi and dysplastic nevi as precursors of cutaneous melanoma. In addition, lesions diagnosed clinically as simple lentigo and solar lentigo may be important as potential precursors of melanoma, particularly in the elderly.

The Causes of Malignant Melanoma: Results from the West Australian Lions Melanoma Research Project

In Australia malignant melanoma ranks forth among cancers as a cause of morbidity and premature death (Armstrong 1985). For this reason, and because the State of Western Australia has one of the highest incidence rates of melanoma in the world (Holman et al. 1980), we undertook a multidisciplinary research program embracing the epidemiology, histopathology, and clinical management of melanoma. A major component of our research was a population-based case-control study in which constitutional traits, sunlight exposure, hormones, diet and other possible causal factors were evaluated. We have already published several reports of the results relating to particular subject areas (Holman and Armstrong 1983, 1984 a, b; Holman et al. 1984 b, 1985; English et al. 1985). In this report we aim to bring together in summary form the key results of the project to date and to present new data on diet and other factors.

Melanocytic tumors of uncertain malignant potential: results of a tutorial held at the XXIX Symposium of the International Society of Dermatopathology in Graz, October 2008.

Several reports demonstrated the difficulties and lack of agreement in the histopathologic diagnosis of particular melanocytic tumors (atypical Spitz tumors, atypical blue nevi, deep penetrating nevi). These lesions are often referred to as “melanocytic tumors of uncertain malignant potential” (MELTUMP). We studied a large number of such tumors to find out whether repeatable histopathologic criteria for distinction of benign from malignant cases exist. Fifty-seven cases of MELTUMP were classified within 3 groups according to behavior as follows: (a) favorable (no evidence of metastatic disease after a follow-up of ≥5 y), (b) unfavorable (tumor-related death and/or large metastatic deposits in the lymph nodes and/or visceral metastases), (c) borderline (small nodal deposits of tumor cells ≤0.2 mm). There were no significant differences in tumor thickness and presence or absence of ulceration between the different groups. The only 3 histopathologic criteria that were statistically different between the groups of favorable and unfavorable cases were presence of mitoses, mitoses near the base, and an inflammatory reaction, all of them found more frequently in cases with unfavorable behavior. The major outcome of this study of a series of “MELTUMPs” suggests as a preliminary observation that these lesions as a group exist and that they may be biologically different from conventional melanoma and benign melanocytic nevi. The terminology remains highly controversial, reflecting the uncertainty in classification and interpretation of these atypical melanocytic tumors.

Case-control study of sun exposure and squamous cell carcinoma of the skin

We conducted a case‐control study of sun exposure and squamous cell carcinoma (SCC) of the skin within a population‐based, longitudinal study of skin cancer. Cases had histopathologically confirmed SCC. Subjects were interviewed about their lifetime sun exposure, including exposure to the site of the SCC (sites for controls were assigned randomly). Analysis was restricted to 132 cases and 1,031 controls born in Australia and with no ancestors from southern Europe. The total site‐specific exposure was strongly related to risk of SCC; the odds ratio increased to a maximum of 3.3 at 65,000 hr of exposure before falling slightly. Site‐specific exposure during childhood and adolescence was more strongly associated with SCC than exposure during adulthood. An intermittent pattern of weekly sun exposure was not associated with SCC and the odds ratios for hours of exposure on vacation were close to unity. The number of blistering sunburns to the site was positively associated with SCC. Use of sunscreens and hats showed inconsistent effects. Sun exposure, especially during childhood and adolescence, increases the risk of SCC. The pattern of exposure appears to be unimportant, despite the association with sunburn, which may simply be an indicator of the skins sensitivity to sunlight. Int. J. Cancer 77:347–353, 1998.

Demographic characteristics, pigmentary and cutaneous risk factors for squamous cell carcinoma of the skin: A case-control study

We conducted a case‐control study of squamous cell carcinoma of the skin (SCC) in a cohort of people followed from 1987 to 1994. Subjects were residents of Geraldton, Western Australia, who were between 40 and 64 years of age in 1987. On 2 occasions, in 1987 and 1992, dermatologists examined participants for skin cancers. Subjects were also asked on several occasions about skin cancers that they had had treated. Migrants to Australia had reduced risks of SCC. Furthermore, people who migrated to Australia early in life or, equivalently, lived in Australia for a long time had a higher risk than immigrants who arrived later in life or more recently. People who had southern European ancestry had a much lower risk of SCC than other subjects, most of whom were of British or northern European origin. Among Australian‐born subjects of British or northern European ancestry, the skins sensitivity to sunlight was strongly associated with SCC. The pigmentary traits of hair colour, eye colour and skin colour showed weaker associations. The degree of freckling on the arm was strongly predictive of risk. The risk of SCC increased strongly with increasing evidence of cutaneous solar damage and was most strongly associated with the number of solar keratoses. Our results show that sensitivity to sunlight and high levels of exposure to sunlight are important determinants of the risk of SCC. Int. J. Cancer 76:628–634, 1998.© 1998 Wiley‐Liss, Inc.

p16 and p21WAF1 protein expression in melanocytic tumors by immunohistochemistry

To determine whether variation in the level of expression of p16 and p21WAF1 (p21) is associated with critical stages in cutaneous melanoma development or progression, the expression of these antigens was analyzed by immunohistochemistry in 110 benign and malignant melanocytic lesions. Differential expression of p16 protein has been reported in cutaneous melanocytic lesions, with loss of expression associated with the invasive stage of tumor development. Expression of p16 was seen in 31 of 35 benign melanocytic tumors (89%), 11 of 12 in situ melanomas (92%), 19 of 38 invasive primary melanomas (50%), and 16 of 25 metastatic melanomas (64%). There was a significant difference in the expression level of p16 observed in in situ versus invasive primary melanomas (p = 0.006), which is consistent with loss of normal p16 activity occurring in association with malignant tumor invasion. Overall, p21 levels were found to be low or undetectable in the majority of benign lesions, with greater p21 expression seen in malignant tumors. p21 was expressed in 28% of nevi, 60% of in situ melanomas, 61% of invasive melanomas, and 48% of metastatic melanomas. Among primary invasive tumors, the frequency of p21 expression increased with level of invasion (p < 0.01) and with increasing thickness (p < 0.01). However, differences in p21 expression were not clearly related to a particular stage of melanoma development.

p53 gene mutation and expression in naevi and melanomas

Mutations of the p53 tumour suppressor gene are common to many human malignancies. Although increased p53 expression has been observed in cutaneous malignant melanoma, mutations of the p53 gene appear to be infrequent. We ex-amined 140 benign and malignant paraffin-embedded melanocytic lesions for p53 protein expression by immunohistochemistry, using the monoclonal anti-p53 antibody DO-7 and a microwave method of antigen retrieval. Fifteen naevi and 25 melanomas were further analysed for p53 mutations within exons 5–8 of the p53 gene. DNA was extracted from paraffin sections and screening for mutations was carried out using PCR-SSCP. We demonstrated p53 protein expression in 33% of naevi (17 out of 51), 35% of primary melanomas (20 out of 58), and 70% of metastatic lesions (15 out of 21). p53 expression in benign lesions was weaker than in malignant lesions in intensity and percentage of cells staining. p53 protein expression in melanomas increased in intensity and percentage of cells staining with tumour progression. In 25% (three out of 12) of metastatic melanomas p53 mutations were detected by PCR-SSCP and increased expression of p53 protein was observed in these tumours. p53 gene mutations were not detected in any benign melanocytic lesions. We demonstrate that antigen retrieval techniques increase p53 immunoreactivity in paraffin embedded melanocytic tissues. p53 protein expression in melanomas increases with depth of tumour invasion. As p53 gene mutations occur infrequently in malignant melanoma, other mechanisms are proposed to influence p53 protein expression in melanocytic lesions.

Inter‐observer variation between pathologists in the classification of cutaneous malignant melanoma in Western Australia

Inter‐observer variation between six pathologists in their application of histological classifications during a survey of cutaneous malignant melanoma was analysed using kappa statistics. The highest levels of adjusted agreement were attained for tumour thickness and the presence of ulceration; intermediate levels were achieved on cross‐sectional profile, level of invasion, histogenetic type, solar elastosis and the presence of an associated benign melanocytic lesion; agreement on other histological features of melanoma tended to be relatively poor. The problems experienced in the interpretation of these classifications are discussed and suggestions for their improvement are offered.

Primary cutaneous neuroendocrine carcinoma (Merkel cell tumor) : an adnexal epithelial neoplasm

We report 18 cases of primary cutaneous neuroendocrine carcinoma (CNEC, Merkel cell tumor) that occurred mainly in the sun-exposed skin of elderly patients as dermal and subcutaneous masses of generally monomorphic cells with foci of pronounced pleomorphism. All 18 cases showed immunoreactivity for neuron-specific enolase (NSE), whereas 16 of them showed immunoreactivity for another neuroendocrine marker, protein gene product 9.5 (PGP 9.5). Positivity for PGP 9.5 was more intense and more sharply localized to tumor cells than the staining for NSE. Immunoreactivity for keratins detected by AE1/AE3 and CAM 5.2 monoclonal antibodies was found in 16 and 15 cases, respectively, with prominent paranuclear globular staining. One case stained positively for S-100 protein; all were negative for leukocyte common antigen (LCA). Typical ultrastructural features of neuroendocrine differentiation were noted in all of 14 tumors examined. Morphological and immunohistochemical similarities between these neoplasms and pulmonary small-cell anaplastic carcinoma, now thought to be of bronchial basal cell origin, suggest that CNEC are also derived from epithelium. In addition, their dermal location suggests that this epithelium is likely to be adnexal rather than epidermal.