Biomarker p16(INK4a) on paraffin sections prepared from cervical brush samples highlights nuclear changes resulting in unquestionable cytohistodiagnosis

To optimize the morphology of pl6-positive atypical and (pre)neoplastic cells in paraffin cytoblock sections with the aim to minimize equivocal diagnoses on cytology samples. Patients with negative cytology results or results within normal limits (WNL) (n=38), atypical squamous cells of undetermined significance (ASCUS) (n=25) and high grade squamous intraepithelial lesion (HSIL) (n=16) were selected. The residual material of the cervical brush samples was processed to cytoblock paraffin sections and stained for pl1. The cytohistodiagnosis of the pl1-stained paraffin sections was based on the cytologic and histologic morphology. Of the 38 cytologically negative cases, only 4 contained afe w faintly positive pl61cells. Of the 25AS CUS cases, I 1as cytohistologically upgraded to low grade squamous intraepithelial lesion (LSIL). All 16 HSIL cases contained cells with outspoken diffuse positive immunostaining, highlighting chromatin clumping in the (pre)malignant cells. In the paraffin sections the tissue fragments showed architecture consistent with that of HSIL. The nuclear to cytoplasmic ratio in the HSIL was severely disturbed. Cervical brush samples allow an unequivocal cytohistodiagnosis based on the (pre)malignant nuclear changes highlighted by the p16 staining of the paraffin sections.