Testis, Rete Testis - Hyperplasia

Image of rete testis hyperplasia in the testis from a male CD-1 mouse
Testis, Rete testis - Hyperplasia in a male CD1 mouse. Proliferation of lining epithelium is present in the dilated rete testis. (Photograph courtesy of Dr. D. Creasy.)
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Image of rete testis hyperplasia in the testis from a male CD-1 mouse
Testis, Rete testis - Hyperplasia in a male CD1 mouse. Hyperplasia of the lining epithelium of the rete testis. (Photograph courtesy of Dr. D. Creasy.)
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Hyperplasia of the rete testis epithelium occurs as a focal or multifocal lesion and can be seen as an occasional incidental lesion in rats but more commonly in CD1 mice. The hyperplastic epithelium generally forms papillary or knob-like projections into the lumen with no compression of surrounding tissue ( Figure 1image opens in a pop-up window and Figure 2image opens in a pop-up window ). The hyperplasia is frequently accompanied by cystic dilation of the rete ducts and sperm stasis ( Figure 2image opens in a pop-up window ). Proliferative lesions of the rete testis have been observed in response to prenatal exposure to diethyl stilbestrol. The finding needs to be distinguished from rete testis adenoma, where extensive papillary structures and supporting stroma cause compression of the surrounding tissue.


Rete testis hyperplasia should be diagnosed and graded whenever present. Bilateral involvement should be recorded when present. Associated lesions such as sperm stasis and seminiferous tubule dilation should not be diagnosed separately unless warranted by severity, but should be described in the pathology narrative.


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