Atypia / premalignant / preinvasive lesions
Atypical squamous cells of undetermined significance (ASC)

Author: Marilin Rosa, M.D. (see Authors page)

Revised: 10 April 2017, last major update June 2011

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PubMed search: cervix Atypical squamous cells of undetermined significance (ASC)

Cite this page: Atypical squamous cells of undetermined significance (ASC). PathologyOutlines.com website. http://pathologyoutlines.com/topic/cervixcytologyatypicalsquamouscells.html. Accessed April 24th, 2017.
Definition / General
  • May be neoplastic (HPV related, LSIL, HSIL) or reactive
  • Formerly called ASCUS
  • ASC is subdivided into atypical squamous cells of undetermined significance (ASC-US) and atypical squamous cells, cannot rule out a high grade lesion (ASC-H)
Clinical Features
  • Repeat cytology, colposcopy, or perform DNA testing for high risk HPV subtypes according to age group or previous history of dysplasia
Cytology Description
  • Nuclear changes are more marked than reactive, less than LSIL
  • Nucleus is 2.5-3x size of intermediate cell nucleus or 1.5x size of mature metaplastic cell nucleus
  • In perimenopausal women (40-55 years), cells with bland nuclear enlargement (2-3x size of intermediate cell nuclei), smooth nuclear membranes and fine chromatin are likely to be negative for SIL/malignancy (Am J Clin Pathol 2005;124:58)
Cytology Images

Various images

Cytologic changes NOT typical of ASC-US

Mild nuclear enlargement

Nuclear enlargement with atrophy

Nuclear enlargement with hyperchromasia and irregular nuclear membranes


Degenerative atypical cells

Additional References