Inmunohistoquímica de la proteína p16INK4a en biopsias y extendidos cervicovaginales y su relación con HPV por PCR

Estudios recientes sugieren que la sobreexpresion de p16, determinada por inmunohistoquimica, seria un marcador especifico de celulas escamosas displasicas y neoplasicas con alta asociacion con HPV de alto riesgo. Nuestro objetivo fue correlacionar los hallazgos cito/histologicos con la expresion de p16 y el subtipo de HPV por PCR. Seleccionamos 95 biopsias de cuello uterino y 4 legrados endocervicales de 99 individuos, y 30 extendidos cervicovaginales de otros 30 individuos, que se dividieron segun el diagnostico morfologico. Inmunomarcamos cortes del material incluido en parafina y los extendidos con el kit CINtecT p16INK4a (DAKO). Evaluamos HPV por PCR utilizando 25/99 biopsias con lesion intraepitelial escamosa de bajo grado. Observamos marcacion positiva para p16 en 1/35 biopsias (2.9%) y 1/11 extendidos (9%) en los grupos sin HPV ni displasia; 16/25 biopsias (64%) y 6/10 extendidos (60%) en aquellos con lesion de bajo grado y 38/39 biopsias (97.4%) y 8/9 extendidos (89%) en los grupos con lesion de alto grado y carcinoma escamoso. Todas las muestras con HPV-6/11 fueron negativas o positivas focales para p16, en tanto que aquellas con HPV-18 u otros subtipos fueron mayoritariamente positivas de tipo difuso. Concluimos que la expresion de p16 presenta alta correlacion con el diagnostico cito/histologico y alta asociacion entre la marcacion difusa y la presencia de HPV de alto riesgo, aportando mayor objetividad en casos dudosos y ayudando a seleccionar grupos de individuos con riesgo de progresion de enfermedad, con un costo aceptable para estudiar grandes grupos.(AU) Recent studies suggest that p16 overexpression determined by immunohistochemistry would be a specific marker for neoplastic and dysplastic squamous cells associated with high-risk HPV. The purpose of this study was to assess the correlation between cyto-histological findings, p16 expression and HPV subtype. A total of 99 biopsies were selected, 4 endocervical curettages and 95 uterine cervix biopsies, as well as 30 cervicovaginal smears from other 30 patients. The samples were divided according to the morphological diagnosis. Paraffin-embedded sections and cervicovaginal smears were immunostained using the CINtecT p16INK4a Cytology Kit (DAKO). HPV was analyzed by PCR in 25 of the 99 biopsies with low-grade squamous intraepithelial lesion. Among those patients with neither HPV nor dysplasia, 1 of 35 (2.9%) biopsies and 1 of 11 (9%) smears were positive for p16. Sixteen of 25 (64%) biopsies and 6 of 10 (60%) smears of the low-grade lesion cases, and 38 of 39 (97.4%) biopsies and 8 of 9 (89%) smears of the high-grade lesion and squamous carcinoma were positive for p16. All cases of HPV-6/11 were negative or focally positive for p16. Most cases of HPV-18 or other subtypes were diffusely positive. Our results indicate that p16 expression is highly correlated with cyto-histological diagnosis, and is associated with diffuse staining and high-risk HPV. This technique provides greater objectivity in doubtful cases, and helps select patients at risk of disease progression at an acceptable cost when used in large populations.(AU)