Type of Preparation: Conventional Magnification: High Clinical History: 30 year old woman with an interpretation of "atypical endocervical cells (AGC)" on a previous Pap smear Interpretation: HSIL with extension into endocervical gland Cytomorphologic Criteria: At the far right in this cluster of cells, one can visualize benign endocervical cells characterized by columnar shape, eccentric nuclei with smooth membranes and fine chromatin. Note also the residual mucin vacuoles at the left upper edge of the cell cluster. In comparison the cells on the left are large with hyperchromatic nuclei show much overlapping When HSIL. lesions involve endocervical glands, they may show features that overlap with those of AIS. Explanatory Notes: HSIL with glandular extension is often diagnosed as AGC or may be misinterpreted as endocervical neoplasia. Locating isolated abnormal squamous cells offers clues as to the origin of this lesion.