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Uterus - Endometrial Stromal Polyp

Image of endometrial stromal polyp in the uterus from a female Harlan Sprague-Dawley rat in a chronic study
Uterus - Endometrial stromal polyp in a female Sprague-Dawley rat from a chronic study. A pedunculated polyp is present in the uterine lumen.
Figure 1 of 4
Image of endometrial stromal polyp in the uterus from a female Harlan Sprague-Dawley rat in a chronic study
Uterus - Endometrial stromal polyp in a female Sprague-Dawley rat from a chronic study (higher magnification of Figure 1). There is endometrial congestion adjacent to the polyp.
Figure 2 of 4
Image of endometrial stromal polyp in the uterus from a female Harlan Sprague-Dawley rat in a chronic study
Uterus - Endometrial stromal polyp in a female Sprague-Dawley rat from a chronic study. There is a polyp with an infarcted area.
Figure 3 of 4
Image of endometrial stromal polyp in the uterus from a female Harlan Sprague-Dawley rat in a chronic study
Uterus - Endometrial stromal polyp in a female Sprague-Dawley rat from a chronic study. There is superficial decidual alteration of a stromal polyp.
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comment:

Stromal polyps are composed of areas of loosely organized stromal cells with blood vessels and occasionally a few trapped glands ( Figure 1image opens in a pop-up window , Figure 2image opens in a pop-up window , Figure 3image opens in a pop-up window , and Figure 4image opens in a pop-up window ). They are pedunculated masses that protrude into the uterine lumen. Stromal polyps are usually covered with simple epithelium. Occasionally, they become infarcted ( Figure 3image opens in a pop-up window ), and sometimes decidual alteration is evident ( Figure 4image opens in a pop-up window ). Ulceration, edema, and inflammation are also occasionally seen. Stromal polyps can arise from the cervix. They are relatively common in F344/N rats and B6C3F1 mice and tend to occur in older animals. They may represent localized areas of hyperplasia and have been associated with hormonal stimulation. Stromal polyps are considered to be preneoplastic lesions. 

The number of glands within the polyps can vary, and some pathologists propose that those with numerous glands be classified separately as endometrial glandular polyps. The glands within such polyps may be hyperplastic. Until more is learned about these lesions, we recommend that all endometrial polyps be recorded as stromal polyps. 

Vaginal polyps may extend through the cervix into the uterus and so must be differentiated from endometrial polyps. Vaginal polyps are composed of stroma but are covered by stratified squamous  epithelium like the vagina.

It is important to differentiate polyps from epithelial neoplasms and malignant mesenchymal neoplasms (e.g., stromal sarcomas). Adenomas and adenocarcinomas may be exophytic and are distinguished from polyps by more complex epithelial structures, atypia, and/or pleomorphism. Adenomas are composed of focal accumulations of single layers of cuboidal to columnar cells with scant intervening stroma. Adenocarcinomas are masses composed of multiple layers of cells in glandular or papillary formations. The epithelium in adenocarcinomas is less differentiated than that of adenomas and displays moderate cellular pleomorphism and atypia. Stromal sarcomas are distinguished from polyps by greater cellularity and more prominent nuclei of the pleomorphic cells. Stromal sarcomas often invade adjacent uterine tissue.

recommendation:

Uterus - Endometrial stromal polyp should be diagnosed but need not be graded. These should be diagnosed as stromal polyps regardless of the number of glands within them. The prominence of the glandular component may be described in the pathology narrative. Changes within the polyp, including ulceration, edema, and inflammation, should not be diagnosed separately but should be described in the narrative.

references:

Davis BJ, Dixon D, Herbert RA. 1999. Ovary, oviduct, uterus, cervix and vagina. In: Pathology of the Mouse: Reference and Atlas (Maronpot RR, Boorman GA, Gaul BW, eds). Cache River Press, Vienna, IL, 409-444.

Greaves P. 2012. Female genital tract. In: Histopathology of Preclinical Toxicity Studies: Interpretation and Relevance in Drug Safety Evaluation, 4th ed. Elsevier, Amsterdam, 667-724.

Leininger JR, Jokinen MP. 1990. Oviduct, uterus and vagina. In: Pathology of the Fischer Rat (Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, CA, 443-459.

Maekawa A, Maita K. 1996. Changes in the uterus and vagina. In: Pathobiology of the Aging Mouse (Mohr U, Dungworth DL, Capen CC, Carlton WW, Sundberg JP, Ward JM, eds). ILSI Press, Washington, DC, 469-480.

National Toxicology Program. 1978. NTP TR-143. Bioassay of 1,5-Naphthalenediamine for Possible Carcinogenicity (CAS No. 2243-62-1). NTP, Research Triangle Park, NC.
Abstract: http://ntp.niehs.nih.gov/go/10029

National Toxicology Program. 1989. NTP TR-368. Toxicology and Carcinogenesis Studies of Nalidixic Acid (CAS No. 389-08-2) in F344/N Rats and B6C3F1 Mice (Feed Studies). NTP, Research Triangle Park, NC.
Abstract: http://ntp.niehs.nih.gov/go/8876

National Toxicology Program. 2010. NTP TR-559. Toxicology and Carcinogenesis Studies of 2,3',4,4',5-Pentachlorobiphenyl (PCB 118) (CAS No. 31508-00-6) in Female Harlan Sprague-Dawley Rats (Gavage Studies). NTP, Research Triangle Park, NC.
Abstract: http://ntp.niehs.nih.gov/go/33539

Yuan YD. 1991. Female reproductive system. In: Handbook of Toxicologic Pathology (Haschek WM, Rousseaux CG, eds). Academic Press, San Diego, CA, 891–935.