JPC SYSTEMIC PATHOLOGY
REPRODUCTIVE SYSTEM
January 2019
R-M01

Signalment:  Adult female cat

HISTORY:  This cat was clinically normal and pregnant

HISTOPATHOLOGIC DESCRIPTION (Slide A):  Uterus and placenta:  The uterus is complete with a perimetrium, myometrium and endometrium.  Extending from the endometrium are maternal septa that interdigitate with the labyrinthine villar projections from the fetal chorioallantois. Below these interdigitations, the endometrium is composed of a deep glandular zone consisting of dilated uterine glands and cellular debris and the superficial junctional zone with terminal lamellae, maternal vessels, and glandular secretions.  Fetal tissues consist of the allantoic membrane, normal edematous allantochorionic connective tissue containing large vessels, and  lamellae/villi lined by trophoblasts.  Multifocally, maternal vascular endothelium directly apposes fetal trophoblasts, seperated by a thin acellular layer of stroma.  In an area of smooth placentation (chorion laeve), the fetal tissues are characterized by sparse to indistinguishable allantochorionic connective tissue and a chorionic epithelial layer consisting of columnar cells with basal nuclei.

MORPHOLOGIC DIAGNOSIS:  Uterus, placenta:  Essentially normal tissue, breed unspecified cat, feline.

Signalment (JPC # 2879193):  Adult, female, horse

HISTORY:  This horse was clinically normal and pregnant.

HISTOPATHOLOGIC DESCRIPTION (Slide B):  Uterus and placenta: The uterus is complete with a perimetrium, myometrium and endometrium. The endometrium is composed of a glandular zone consisting of dilated uterine glands containing cellular debris, separated by loosely arranged connective tissue. Extending from the endometrium are crypts, which are formed by the interdigitation of chorioallantoic villi with the endometrium in a microcotyledonary arrangement,imparting a nodular appearance to the materal fetal interface. Fetal tissues include the allantoic epithelium (lining the allantoic cavity), edematous allantochorionic connective tissue containing large vessels,fetal microcotyledons lined by trophoblastic epithelium that interdigitates with the maternal endometrium to form an epitheliochorial attachment.

MORPHOLOGIC DIAGNOSIS:  Uterus, placenta:  Essentially normal tissue, breed unspecified, equine.

Signalment (JPC #4056477-00):  Adult, female, sheep

HISTOPATHOLOGIC DESCRIPTION (Slide C):  Uterus and placenta:  Two sections are present, with one exhibiting a placentome and the other the intercotyledonary/ intercaruncular space. In the placentome, the uterus is complete with a perimetrium, myometrium and endometrium. The endometrium is composed of a glandular zone consisting of flattened uterine glands separated by loosely arranged connective tissue. The surface of the endometrium is forming crypts (caruncle) which interdigitate with the fetal chorionic villous projections (cotyledon) which together form the placentome. The chorionic villi are lined by trophoblastic epithelial cells that multifocally have lost cellular borders to form multinucleated syncytiotrophoblasts which contact the maternal endometrium to form an epitheliochorial attachment. Subjacent to the trophoblast epithelium is the edematous allantois connective tissue containing large vessels and areas of hemorrhage (marginal hematoma). The allantoic epithelium is indistinct. The intercaruncular uterus has attenuated or indistinct endometrium, flattened endometrial glands and prominent myometrium. The intercotyledonary chorioallantois is thin with an edematous stroma lined by flattened chorionic epithelium.

MORPHOLOGIC DIAGNOSIS:  Uterus, placenta and placentome:  Essentially normal tissue, breed unspecified, ovine

Signalment (JPC # 4055712-00):  Adult, female, dog

HISTOPATHOLOGIC DESCRIPTION (Slide D):  Placenta: The chorioallantois is present forming a labyrinthine or lamellar interconnecting network of trophoblast epithelial cells and multifocal multinucleated syncytiotrophoblasts often in direct apposition to maternal blood vessels which are lined by hypertrophic endothelial cells. There are multifocal areas of hemorrhage (stangant materal blood), with formation of hematoidan crystals, and maternal vessels are often congested. When apparent, the endometrial epithelium and connective tissue are replaced by necrotic cell debris and fibrin. Subjacent to the chorioallantoic trophoblastic epithelium, the allantois is edematous and contains numerous congested blood vessels.  The allantoic epithelium is flattened and attenuated or multifocally cuboidal.

MORPHOLOGIC DIAGNOSIS:  Uterus, placenta:  Essentially normal tissue, breed unspecified, canine.

Signalment (JPC # 4070866-00):  7-year-old female paint horse

HISTORY:  This horse was diagnosed with peritonitis and pyrexia prior to necropsy

HISTOPATHOLOGIC DESCRIPTION (Slide E): Uterus, endometrial cup: The endometrium is multifocally lost and endometrial glands are widely separated by numerous large, often elongated specialized trophoblasts with abundant eosinophilic vacuolated cytoplasm and one or two vesiculate nuclei with a single prominent nucleolus. Trophoblasts are admixed with numerous lymphocytes and plasma cells with fewer macrophages, multinucleated giant cells and neutrophils. Endometrial glands are often ectatic and contain moderate to abundant homogenous eosinophilic material (secretory product). Large vessels are congested and the lamina propria is edematous and contains dilated lymphatics. There are lymphocytes and plasma cells occasionally surrounding vessels in the lamina propria and myometrium. 

MORPHOLOGIC DIAGNOSIS:  Uterus, endometrial cups:  Essentially normal tissue, paint, equine.

GENERAL DISCUSSION:

CLASSIFICATION OF PLACENTATION:

Classification based upon the fetal extraembryonic membranes:

Classification based upon the degree of uterine destruction:

Classification based upon the area of fetal-maternal attachment:

Classification based upon the fetal-maternal interhemal barrier:

Configuration of maternal and fetal tissue interface:

Summary of placentation by species:

 

Fetal/Maternal Attachment

Maternal/Fetal Interface

Uterine Distruction

Interhemal Barrier

Pig

Diffuse

Folded

Nondeciduate

Epitheliochorial

Horse

Diffuse

Villous

Nondeciduate

Epitheliochorial

Ruminant

Cotyledonary

Villous

Nondeciduate

Epitheliochorial

Carnivore

Zonary

Labyrinthine

Deciduate

Endotheliochorial

Primate

Discoid

Villous

Deciduate

Hemochorial

Rodent

Discoid

Labyrinthine

Deciduate

Hemochorial

Placental variations in individual species:

Pig

Horse

Ruminant

Carnivores:

Anomalies and abnormalities of the placenta:

REFERENCES:

  1. Aughey E, Frye FL. Comparative Veterinary Histology. London, England: Mason Publishing; 2001: 196-203.
  2. Bacha WJ, Bacha LM. Color Atlas of Veterinary Histology. 3rd Ames, IA: John Wiley & Sons, Ltd.; 2012:244, 254-258.
  3. Banks WJ. Applied Veterinary Histology. 3rd ed. St. Louis, MO: Mosby; 1993:457-468.
  4. Benirschke K. Comparative Placentation. Available at http://placentation.ucsd.edu/introfs.html, Accessed December 20, 2018.
  5. Lewis SH, Benirschke K. Placenta. In: Mills SE, ed. Histology for Pathologists. 3rd Philadelphia, PA: Lippincott Williams & Wilkens; 2007:1095-1129.
  6. Ross MH, Pawlina W. Histology A Text and Atlas. 5th Baltimore, MD: Lippincott Williams & Wilkens; 2006:796-801.
  7. Young B, O’Dowd G, Woodford P. Wheater’s Functional Histology. 6th Philadelphia, PA: Elsevier; 2014:370-376.


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