Disease progression in patients with thin cutaneous melanomas (tumour thickness < or = 0.75 mm): clinical and epidemiological data from the Tumour Center Munich 1977-98.

BACKGROUND

Although survival in patients with thin melanomas (tumour thickness < or = 0.75 mm) is usually excellent, thin melanomas have the potential to metastasize.

OBJECTIVES

To determine risk factors for the development of disease progression in patients with thin cutaneous melanomas.

METHODS

A retrospective study was performed between 1977 and 1998 to identify risk factors for the development of disease progression in 2302 patients with cutaneous melanoma with tumour thickness < or = 0.75 mm, diagnosed and treated at the Department of Dermatology and Allergology, Ludwig-Maximilians University, Munich, Germany. The Kaplan-Meier method was used to estimate the influence of different clinical characteristics for the occurrence of first progression during 10 years of follow-up.

RESULTS

An analysis of the data from 6298 patients with cutaneous melanoma identified 2302 patients (37%) who presented with cutaneous melanoma with a tumour thickness < or = 0.75 mm, without clinical signs of metastasis at initial diagnosis (clinical stage Ia). A small subgroup of our patients (77 of 2302) developed metastatic disease during the follow-up period. The estimated rate of occurrence of metastasis after 10 years of follow-up was 4.7%. The mean follow-up time was 62 months (median 46). Of these 77 patients, 16 experienced progression at the primary tumour site and 32 presented with regional lymph node metastases. Twenty-eight patients primarily developed systemic metastases (seven patients with and 20 without regional lymph node metastases, one patient with regional lymph node metastases and local recurrence). In one patient the primary site of metastatic disease was not reported. Clinical characteristics included age, sex of the patient and different subtypes of cutaneous melanoma: superficial spreading melanoma, nodular melanoma, acrolentiginous melanoma (ALM) and lentigo maligna melanoma (LMM). Male patients and patients with LMM or ALM were significantly over-represented (P = 0.02 and P = 0.002). In the group of 77 patients with thin melanomas (< or = 0.75 mm), local recurrence was over-represented as compared with those with melanomas > 0.75 mm. No difference in group was found for overall survival after the occurrence of lymph node metastasis as the first manifestation of disease progression.

CONCLUSIONS

Thorough follow-up and skin examination is recommended for a subgroup of patients with thin tumours, which consists of male patients with LMM or ALM located in the head and neck region.