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Normal cells / non-neoplastic findings

Squamous metaplasia

Reviewer: Farnaz Hasteh, M.D., UCSD Medical Center (see Reviewers page)
Revised: 6 May 2014, last major update March 2011
Copyright: (c) 2006-2011, PathologyOutlines.com, Inc.


● Common metaplastic process that occurs in transformation zone


● Common during puberty, pregnancy and postpartum


● During the reproductive years, the transformation zone (where metaplasia occurs) is distal to external cervical os
● In the postmenopausal years, the T zone may become more proximal, and within the endocervical canal


● Due to proliferation of reserve cells under columnar cells
● First step in the process is reserve cell hyperplasia; then squamous differentiation begins which is immature; then mature squamous metaplasia, which fills endocervical glands
● Promoted by increased acidity at puberty, inflammation, polyps, OCP (oral contraceptive) use

Prognostic factors

● Endocervical and metaplastic cells in the Pap test is associated with higher detection rates of HSIL (Diagn Cytopathol 2009;37:241)
● Atypical metaplastic cells in the Pap test is associated with SIL, especially HSIL (Cancer 2001;93:16, Cancer 1999;87:56)

Cytology description

Immature squamous metaplasia
● Associated with endocervical cells
● Arranged in cobblestone pattern (jigsaw pattern) or singly
● Parabasal like cells with dense, dark cytoplasm reduced in quantity, increased N/C ratio
● Blue cytoplasm with sharp cell border; often cytoplasmic vacuoles
● Round to oval nuclei with smooth membrane and fine chromatin
● Spidery forms are common
● Nucleoli are present if reactive process
● May resemble reserve cell hyperplasia
● In liquid based cytology, they have higher N/C ratio and can mimic HSIL

Mature squamous metaplasia
● Resembles intermediate cells, but with denser cytoplasm and rounded cell outlines
● Normal N/C ratio

Cytology images

Various images

Mature squamous metaplasia

Immature squamous and transitional (urothelial) metaplasia

Contributed by: Dr. Marilin Rosa, University of Florida (USA)

Differential diagnosis

● Atrophy and parabasal cells

End of Cervix-cytology > Normal cells / non-neoplastic findings > Squamous metaplasia

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