Merkel cell carcinoma: a clinicopathological study of 34 patients

Abstract

Background: Merkel cell carcinoma (MCC) is a rare cutaneous malignant tumour. Its natural course is fast progression of the primary tumour and rapid regional metastasis.

Methods: The pathological archives of Helsinki University Hospital and Vaasa Central Hospital were reviewed from 1987 to 2001. Specimens were re-evaluated by two pathologists and size was measured from primary tumours. Multivariate analysis was performed for age, sex, primary tumour size, and method of initial surgery, development of metastatic disease and development of local recurrence. Overall survival (OS) was calculated by the Kaplan–Meier method.

Results: Of 34 patients, 12 male and 22 female patients, are reported. Their median age was 76.4 years. Half of the primaries were located in the head and neck region. All patients were treated surgically. The mean OS was 2.7 years by the Kaplan–Meier method. The 2-year survival rate was 65% and 5-year rate was 50%. The mean OS for tumour size >2 cm was 1.7 years and for tumour size ≤2 cm 4.48. Poor prognostic factors for OS were: male sex, size of the primary tumour (>2 cm) and metastatic dissemination. A favourable prognosis seemed to correlate to more aggressive surgical management as use of primary excision with split skin graft or reconstruction with a local flap.

Conclusion: MCC affects the elderly patients. In this study, female patients predominated. Primary tumour size >2 cm predicts poorer outcome of the disease. A wide surgical excision is recommended for the primary treatment of MCC.

Introduction

Merkel cell carcinoma (MCC) is also referred as primary neuroendocrine carcinoma, trabecular carcinoma, small-cell carcinoma of the skin or malignant trichodiscoma.1., 2. It is a rare, aggressive, neuroendocrine cutaneous tumour.

In the human adult the Merkel cells are thought to function as slow acting mecanoreceptors, but in the developing embryo their role seems to involve formation of the subepidermal nerve plexus.³ They contain neuron-specific-enolase and so they are easily demonstrated by immunostaining. Toker⁴ described the first five patients with MCC, in 1972. The pathological diagnosis is confirmed with immunohistochemistry usually using cytokeratin 20 (CK-20).5., 6., 7.

The median age at the presentation is 64–68 years. Both sexes are affected but there seems to be a slight male predominance.8., 9., 10., 11., 12. In 50% of patients, the tumour is located in the head and neck region and in 34–40% of the cases it is found in the extremities.13., 14. The natural course is rapid progression of the primary tumour and regional metastasis. Distant dissemination may also occur, to the lungs, liver and bone. Up to 40% of the patients develop a local recurrence, 55% develop regional lymph node metastasis and 36% distant metastasis dissemination. Overall survival (OS) was found to be sex but not age dependent.¹⁵

MCC has been associated with squamous cell carcinoma, basal cell carcinoma of skin; haematological malignancies and with breast and ovarian adenocarcinomas.16., 17. Therapeutic immunosuppression, has also been linked with MCC.18., 19.

The aim of this study was to report our experience of this tumour and its prognostic factors. Tumour related, patient related and also methodological factors were reviewed. The tumour is rare and most published series are small. Guidelines or consensus about management are lacking.