Prognostic value of tumour thickness in cutaneous malignant melanoma

Evidence concerning the accusation that melanoma is overdiagnosed

BACKGROUND

Melanoma is one of the most commonly diagnosed malignancies in the United States and is responsible for the majority of deaths from skin cancer.

OBJECTIVE

Since the 1970s, the incidence of melanoma has risen appreciably while melanoma-specific mortality has remained stable. This has raised a debate about potential overdiagnosis of melanoma. Herein, we review temporal trends in melanoma incidence and mortality and explore factors that may contribute to observed trends, including an aging population in the United States, ultraviolet exposure, increased numbers of biopsies by dermatologists and physician extenders, skin cancer screenings, histopathology criteria, and historic underdiagnosis. Additionally, we discuss melanoma overdiagnosis and the extent to which it may contribute to current trends.

METHODS

The literature was reviewed.

RESULTS

Several factors may contribute to an increased incidence of melanoma, including an aging population, ultraviolet exposure, increased skin biopsies, skin cancer screenings, histopathologic criteria, historic underdiagnosis, and current overdiagnosis.

LIMITATIONS

Further studies are required to determine exactly which tumors are being overdiagnosed, and how to improve patient outcomes with adjustment to physician's practice.

CONCLUSION

The rise in the incidence of melanoma observed since the 1970s is likely multifactorial.

ACP best practice no 162. The histological reporting of melanoma. Association of Clinical Pathologists

The incidence of malignant melanoma has increased steadily over the past 30 years and this type of malignancy is the leading cause of death from cutaneous malignant disease. Cutaneous malignancies, including melanoma, can be detected at a very early stage and a cure is possible with prompt detection and treatment. In recent years, and mainly because of increased awareness of the early detection of melanoma, histopathologists have been exposed more and more to melanocytic lesions. Therefore, it is essential that histopathologists are able to provide a report to the clinician that conveys relevant information in a concise and precise manner. This paper provides a set of guidelines aimed at helping histopathologists with the gross and microscopic description and diagnosis of malignant melanoma.

Malignant melanoma of the conjunctiva

The clinicopathological features of 37 patients with invasive melanoma of the conjunctiva have been studied. Prognosis was closely related to the subsite and size of the primary tumour. Twenty of 21 patients with small localized bulbar neoplasms (95%) and four of six patients with diffuse bulbar melanomas (67%) have survived with no evidence of secondary spread. By contrast, only one of six patients with neoplasms involving the fornix (17%) and two of four (50%) with caruncular melanomas have survived. Metastatic spread was very uncommon in patients with melanomas less than 1.5 mm in maximum thickness, but the outcome of the disease in patients with tumours greater than 1.5 mm was not always bad. Treatment by local excision biopsy was followed by a high rate of conjunctival recurrence (59%). Exenteration of the affected eye guarded against the development of further orbital disease, but was not infrequently followed by the appearance of metastases. Many (62%) of the tumours appeared to have arisen in a pre-existing melanotic lesion or pigmented naevus of long-standing. Histologically, the tumours could be divided into those with an adjacent intra-epithelial component, manifest as atypical melanocytic hyperplasia in the conjunctival epithelium adjacent to the invasive melanoma, and those without (nodular melanoma). However, clear separation of the former group into the subtypes described for cutaneous melanomas proved impossible. Prognosis was not related to the type of melanoma, mitotic rate, cell type or degree of pigmentation.

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.

Measuring melanomas: the Vernier method

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