Subserosal, myometrial lymphatic cyst.

Keywords: lymphatic, cyst, equine, subserosal

This large structure was detected on transrectal palpation.

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Leiomyomas and leiomyosarcomas in the equine myometrium are usually reported as solid structures. However, this was presumed to be a cystic leiomyoma because of its size and location.  Although cystic leiomyomas have not been reported in mares, they do occur  in humans.  Leiomyosarcomas are very rare, making that diagnosis unlikely.

On postmortem examination the massive multilocular cyst at upper left was seen. Histopathological examination by a veterinary pathologist revealed fibrosis surrounding the cysts but no evidence of neoplasia. Therefore this was presumed to be a large lymphatic cyst in an atypical site; myometrial and subserosal rather than endometrial.

References:

G. F. Hoffsis. 1986 Leiomyoma of the Uterus of a Mare. Can Vet J.27: 319–320.

H.M. Nelis et al 2013 Oviductal and uterine leiomyomata in mares. Vlaams Diergeneeskundig Tijdschrift. 82: 81-86

Low,S.C.A. and Chong, C.L 2004 A Case of Cystic Leiomyoma Mimicking an Ovarian Malignancy Ann Acad Med Singapore;33:371-4

Löfstedt, R.M.et al. 1987 Case report. Leiomyosarcoma in the uterus of a mare. Comp. of Cont. Educ. Pract. Vet. 9, 93-96

Berezowski.C, 2002 Diagnosis of a uterine leiomyoma using hysteroscopy and a partial ovariohysterectomy in a mare. Can Vet J. 2002 December; 43(12): 968–970.

Lymphatic lacunae (lymphatic cysts)

Keywords: endometrium, lymphatic, cyst, lacunae, equine, mare, form

General statements on lymphatic lacunae

Lymphatic lacunae (lymphatic cysts) in the endometrium. These are sometimes confused with embryos at 12 to 16 days of gestation. All of the ultrasonographic images on the left are in fact cysts, although two of them resemble embryos. Unlike embryos however, cysts are never mobile!

To avoid confusion during pregnancy diagnosis, lymphatic lacunae should be "mapped" during the first ultrasonographic examination of every breeding season. A diagram suitable for mapping of cysts is shown in the center of this image.

The form in the center can be copied off the large version shown at the bottom of this entry.

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The pathogenesis of lymphatic cysts is obscure but they are not always associated with endometrial fibrosis as is sometimes suggested. Instead, cysts appear to be a sort of lymphatic varicosity, occurring commonly in older mares.

Endometrial cysts are not associated with infertility unless they prevent embryonal migration and thereby block the recognition of pregnancy. Here is an example, an amalgum of images showing a long-standing endometrial cyst in the left uterine horn of a 19 year old mare:

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This was a source of confusion for the referring practitioner because, on some views, it resembled a 40 day pregnancy. It also appeared to be interfering with the migration of embryos in the uterus, resulting in infertility. The cyst is visible here in a transrectal ultrasound image and two endoscopic views (with a normal section of the uterine horn on the extreme right).

An endometrial biopsy was taken from this mare to prognosticate on her ability to maintain pregnancy and to justify laser treatment of the lymphatic lacunum. Her endometrium was normal.

Apart from mild lympangectasis in one area of the biopsy, there was no obvious endometrial fibrosis. Therefore the cyst was ablated using a CO2 endoscopic laser.

Unfortunately this mare was lost to follow-up therefore her post operative fertility is unknown.

A form that is suitable for mapping endometrial cysts when a mare is first examined:

This form is a 300 dpi .jpg file which when printed, will fill a standard 8.5 x 11 inch or A4 page.