same neoplasm.

• Nearly all LGSCs arise in a background of

ovarian benign or borderline serous tumors.

• Most HGSCs are believed to arise from a

precursor lesion, STIC (serous tubal intraepi-

thelial carcinoma), in the tubal mbriae.

• New criteria for primary site assignment in

HGSC include:

- Fallopian tube: STIC present, or mucosal

HGSC present, or part or all of the fallopian

tube is inseparable from tubo-ovarian mass.

- Ovary: both fallopian tubes are separate from

ovarian mass, and no STIC or mucosal HGSC

present in either fallopian tube.

- Tubo-ovarian: fallopian tubes and ovaries are

unavailable for complete examination, and

pathologic ndings are consistent with

extrauterine HGSC.

- Peritoneal (exceedingly rare): both fallopian

tubes and ovaries are fully examined using a

SEE-FIM (Sectioning and Extensively

Examining the FIMbriated end) protocol,

and no gross or microscopic evidence of STIC

or HGSC present in either fallopian tube or

ovary.

- These criteria classify approximately 80% of

HGSCs as primary tubal.

• Serous borderline tumor is the sole recom-

mended term:

- Obsolete terminology no longer recommend-

ed includes atypical proliferative serous

tumor, serous tumor of low malignant

potential, semimalignant serous tumor and

non-invasive LGSC / micropapillary serous

borderline tumor (the latter no longer consid-

ered denitionally synonymous with non-

invasive LGSC).

NON-SEROUS EPITHELIAL

TUMORS

• The following terminology is no longer

recommended:

- Atypical proliferative tumor or tumor of low

malignant potential for all epithelial tumors

(mucinous, endometrioid, seromucinous,

clear cell, Brenner).

Issue 15 || September 2021

WHAT’S NEW

IN GYNECOLOGIC

PATHOLOGY 2021:

OVARY AND

FALLOPIAN TUBE

Gulisa Turashvili

and Ricardo Lastra

Department of Pathology and Laboratory Medicine,

Sinai Health System and University of Toronto, Toronto,

ON, Canada

Department of Pathology, University of Chicago Medical

Center, Chicago, IL, USA

Corresponding Author: Gulisa Turashvili, MD, PhD

Department of Pathology and Laboratory Medicine

Sinai Health System and University of Toronto

Toronto, Ontario, Canada

E-mail: Gulisa.Turashvili@sinaihealth.ca

ORCID

Gulisa Turashvili

https://orcid.org/0000-0001-6125-5865

Ricardo Lastra

https://orcid.org/0000-0003-0691-5685

Abstract

The 5th edition of the World Health Organiza-

tion (WHO) Classication of Female Genital

Tumors was published in 2020. Although the

classication of ovarian and fallopian tube

neoplasms is largely unchanged from the prior

(4th) edition, this newsletter compiles the most

important renements in these organ sites,

including serous and non-serous epithelial

tumors, and sex cord-stromal tumors.

SEROUS NEOPLASMS

• The 4th edition divided serous carcinoma into

low grade (LGSC) and high grade (HGSC) vari-

ants.

• LGSC and HGSC are best considered two

fundamentally different tumors based on their

distinct biology, rather than variants of the

SEROMUCINOUS CARCINOMA

• Previously dened as a carcinoma composed

predominantly of serous and endocervical-type

mucinous epithelium, often with foci showing

clear cells, endometrioid or squamous differen-

tiation.

• Now considered a subtype of endometrioid

adenocarcinoma with mucinous differentiation

(Fig. 1).

NEW VARIANTS OF EPITHELIAL

TUMORS

• Mesonephric-like adenocarcinoma:

- Composed of multiple architectural patterns

(tubular, glandular/pseudoendometrioid,

ductal, papillary, solid), intraluminal eosino-

philic colloid-like material, dense or vesicular

chromatin, inconspicuous nucleoli and

nuclear crowding, and lacking squamous or

mucinous differentiation.

- Positive for GATA3, TTF1, CD10 (luminal)

and PAX8, and negative for hormone

receptors and WT1, with wild-type p53

expression.

- Usually unilateral and diagnosed at stage I in

postmenopausal women.

- May arise from paraovarian mesonephric

remnants or Müllerian carcinomas displaying

secondary mesonephric transdifferentiation.

- May be associated with endometriosis,

cystadenomas, adenobromas, borderline

tumors and LGSC.

Fig. 1. Endometrioid adenocarcinoma with mucinous

differentiation.

WHAT’S NEW

IN PATHOLOGY?

Sponsored by an unrestricted grant from Bio-Techne