P16 protein expression in primary cutaneous melanoma with positive and negative lymph node biopsies: Particular aspects of a study performed at the Hospital de Clinicas de Porto Alegre, Brazil.

BACKGROUND: Cutaneous melanoma dermal invasion, identified through measurement of maximum tumour thickness and sentinel lymph node (SLN) biopsy, is important to establish melanoma prognosis and progression. P16 protein expression has been shown to be a predictive factor for melanoma evolution and prognosis. OBJECTIVE: To investigate p16 protein expression in cutaneous melanomas with and without SLN metastasis. PATIENTS AND METHODS: Sixty-seven paraffin-embedded cutaneous melanoma specimens of patients who had undergone SLN investigation were evaluated from 1995 to 2007. SLN biopsy was negative for metastasis in 34 of these patients (controls); in the remaining 33 patients, SLN biopsy was positive (cases). The expression of p16 protein in the primary tumour was measured using an immunohistochemical assay. The samples were classified according to their nuclear expression. RESULTS: P16 nuclear expression was absent in 14 cases and in 15 controls; P=0.812. There was no statistically significant difference in p16 nuclear expression between cases and controls. CONCLUSIONS: The present study does not support the findings of other studies that suggest p16 protein expression is important in the prognosis of cutaneous melanoma.