Epididymis, Epithelium - Karyomegaly

Image of epithelial karyomegaly in the epididymis from a male B6C3F1 mouse in a chronic study
Epididymis, Epithelium - Karyomegaly. Atypical enlarged nuclei (arrows) in the epididymal epithelium in a male B6C3F1 mouse from a chronic study.
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Image of epithelial karyomegaly in the epididymis from a male B6C3F1 mouse in a chronic study
Epididymis, Epithelium - Karyomegaly. Multiple enlarge nuclei (arrows) in the epididymis in a B6C3F1 mouse from a chronic study.
Figure 2 of 3
Image of epithelial karyomegaly in the epididymis from a male B6C3F1 mouse in a chronic study
Epididymis, Epithelium - Karyomegaly. A karyomegalic nucleus (arrow) is projecting into the duct lumen in a B6C3F1 mouse from a chronic study.
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comment:

Atypical enlarged nuclei (karyomegaly) are most often seen in the epithelium of the ductus deferens, but can also be seen in other parts of the epididymis. Karyomegaly is characterized by epithelial cells that contain large, intensely basophilic staining nuclei that are often indented. It is generally seen as a background finding in mice. There is no evidence that this cell atypia progresses or is preneoplastic.

recommendation:

Karyomegaly should be recorded and graded and should be discussed in the pathology narrative if the incidence and/or severity appears to be related to chemical administration. Indication of bilateral should be provided if appropriate. Correlation with disturbances in other male reproductive organs is recommended to aid interpretation.

references:

Creasy D, Bube A, de Rijk E, Kandori H, Kuwahara M, Masson R, Nolte T, Reams R, Regan K, Rehm S, Rogerson P, Whitney K. 2012. Proliferative and nonproliferative lesions of the rat and mouse male reproductive system. Toxicol Pathol 40:40S-121S.
Abstract: http://www.ncbi.nlm.nih.gov/pubmed/22949412

Haines DC, Chattopadhyay S, Ward JM. 2001. Pathology of aging B6;129 mice. Toxicol Pathol 29:653-661.
Abstract: http://www.ncbi.nlm.nih.gov/pubmed/11794381