Pathology in Practice

Tara R. Scales 1Veterinary Technology Program, LaGuardia Community College, Long Island City, NY 11101

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Kristine Krotec 2Anatomic Pathology, Antech Diagnostics Inc, 9 Schilling Rd, Ste 211, Hunt Valley, MD 21031

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History

Between 2012 and 2016, a paraovarian nodular mass was identified in 6 domestic cats ranging from 7 months to 3 years of age during routine, primary ovariohysterectomy performed by a high-volume spay-neuter surgeon (TRS). During this period, the surgeon performed ovariohysterectomies in 5,825 cats in the Mid-Hudson Valley of New York State. For each of the 6 cats, the history and physical examination findings prior to surgery were unremarkable and no other obvious gross pathological changes were detected during the surgical procedures.

Clinical and Gross Findings

All of the nodular masses in the 6 cats were similar in location and gross appearance. The masses were distinctly separate from primary ovarian tissue and positioned 6 to 10 mm from the ovary, within the mesovarium, and adjacent to the ovarian arteriovenous complex. All of the masses were unilateral, cream to tan, and 2 to 3 mm in diameter (Figure 1). Five of the 6 masses were associated with the left ovary. Each mass was excised completely at the time of ovariohysterectomy as part of the routine removal of the ovary at the level of the ovarian pedicle. The paraovarian masses were a surgical concern in that the nodules appeared grossly similar to ovarian tissue and, in 2 cats, were 9 to 10 mm from the ovary along the mesovarium, the area of the ovarian pedicle typically designated for the placement of hemostatic forceps and ligatures during ovariohysterectomy. A decision to resect and histologically examine each mass was made.

Figure 1—
Figure 1—

Photograph of nodular masses found adjacent to the left ovary in the mesovarium of 2 domestic cats during routine ovariohysterectomy. The masses, in a 3-year-old domestic medium-hair cat (A) and in a 1-year-old domestic shorthair cat (B), have a similar location and appearance. Among 5,825 cats that underwent ovariohysterectomy, a similar mass was identified in 4 other cats.

Citation: Journal of the American Veterinary Medical Association 255, 10; 10.2460/javma.255.10.1117

Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page →

Histopathologic Findings

Each nodular mass was fixed in neutral-buffered 10% formalin,a processed routinely, and stained with H&E stain.b On microscopic evaluation, it was determined that all 6 masses were excised completely and shared similar histopathologic features. Each mass was well circumscribed, possessed a fibrous capsule, and contained 2 predominant cells types: cords of columnar cells that had a sigmoid arrangement next to the capsule (consistent with the zona glomerulosa of the adrenal cortex) and regular straight columns of large, polygonal cells with vacuolated, lipid-containing, eosinophilic cytoplasm (consistent with adrenal cortical zona fasciculata [Figure 2]).

Figure 2—
Figure 2—

Photomicrograph of a section of a nodular mass found in the mesovarium of a 3-year-old domestic cat. Note the distinct capsule (asterisk), zona glomerulosa (dagger), and zona fasciculata (double dagger) consistent with an ectopic adrenocortical rest. H&E stain; bar = 400 μm.

Citation: Journal of the American Veterinary Medical Association 255, 10; 10.2460/javma.255.10.1117

Morphologic Diagnosis and Case Series Summary

Morphologic diagnosis and case series summary: ectopic rest of adrenocortical tissue in the mesovaria of 6 domestic cats.

Comments

Ectopic adrenal rests are congenital abnormalities associated with gonadal tissues in many mammals including cats, horses, and cattle as well as humans.1 With regard to domestic cats, very few reports2,3 have described ectopic adrenal rests, and to the authors’ knowledge, no veterinary medical publications have provided images of their gross appearance in situ. Differential diagnoses for ectopic adrenal masses in cats include ectopic ovarian tissue and luteoma.

The incidence of ectopic adrenal rests in cats has been reported only to a limited extent. In 1978, Bundza and Dukes2 reported an isolated case of an adrenocortical mass in the ovarian ligament of a cat. In 1986, Altera and Miller3 initially reported 17 isolated cases and then, according to McEntee,1 described a prevalence of 2.2% (11/499 cases) in an expanded survey. Given the cases described in the present report, the apparent prevalence of ectopic adrenal rests in a population of 5,825 female cats undergoing ovariohysterectomy was 0.1%. In comparison, the prevalence of this congenital anomaly in horses has been reported to be 9% and 59% in 2 independent studies4,5 with higher prevalence among diseased or pregnant mares.5 In humans, ectopic adrenal rests are rare surgical findings predominantly detected during inguinal exploratory surgery; they are associated with the spermatic cord in 1% to 9.3% of pediatric male patients.6,7

Embryologically, the adrenal gland has 2 origins. The adrenal cortex arises from a mesodermal origin adjacent to the urogenital ridge. The adrenal medulla stems from ectoderm of the neural crest. Late in embryogenesis, the 2 tissues come together as 2 distinct regions within a single capsule to form the complete adrenal gland. Because of the early proximity of adrenocortical and gonadal tissues, small pieces of adrenal cortex may fragment and migrate with the developing gonads (ovaries and testes) during embryogenesis, leading to development of adrenocortical rests adjacent to the mature ovaries and testes.1,3 In the mass samples evaluated in the present report, adrenocortical tissue but no adrenal medullary tissue was detected, likely because of the differences in the embryological paths of the 2 components of the mature adrenal gland.

In healthy carnivores, the adrenal cortex is composed of 3 main zones: the zona glomerulosa, zona fasciculata, and zona reticularis. These zones secrete mineralocorticoids, glucocorticoids, and androgens, respectively. In a normal feline adrenal gland, the outermost zona glomerulosa appears histologically as “curved cords or arcades of columnar cells with acidophilic cytoplasm and small, dark nuclei.”8 This zone is located just under the capsule of the gland. The more extensive zona fasciculata is comprised of “a columnar arrangement of cuboidal or polyhedral cells, which appear foamy due to abundant lipid droplets.”8 The zona reticularis appears histologically as a compact layer of smaller polyhedral cells arranged in cords that often anastomose with one another. This latter zone was not identified histologically in any of the mass samples from the 6 cats of the present report.

In cats, ectopic adrenocortical rests are considered benign, incidental findings of no reported clinical importance. However, in humans and horses, ectopic adrenal masses are considered clinically relevant because of their potential to secrete hormones or be hormone responsive. In horses, hyperplasia of these masses during periods of stress, including disease or pregnancy, has prompted the recommendation for close monitoring of these masses after their identification.4 In humans, rare neoplasms of these structures have been reported as has compensatory ectopic rest hypertrophy in patients who have undergone bilateral adrenalectomy.6,7 These rare clinical effects have prompted the recommendation for surgical excision of ectopic adrenal rests found in humans.

In domestic cats, an adrenal cortical rest adjacent to an ovary poses an intraoperative diagnostic challenge because of its appearance, which is grossly similar to that of ovarian tissue; such masses may be ectopic ovarian tissue that might induce signs of ovarian remnant syndrome if not removed. An adrenal cortical rest adjacent to an ovary also poses a practical surgical challenge because of its position along the mesovarium. Veterinary practitioners should be aware that ectopic adrenocortical rests may be detected and influence surgical decision-making in cats undergoing routine ovariohysterectomy.

Acknowledgments

Funding sources did not have any involvement in the data collection and interpretation or writing and publication of this manuscript. The authors declare that here were no conflicts of interest. The study was performed in compliance with institutional or other guidelines for research in animals.

Footnotes

a.

Richard Allen Scientific, San Diego, Calif.

b.

Processing provided by Antech Diagnostics, Fountain Valley, Calif.

References

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  • 2. Bundza A, Dukes TW. Some heterotropic tissue remnants in domestic animals. Can Vet J 1978;19:322324.

  • 3. Altera KP, Miller LN. Recognition of feline paraovarian nodules as ectopic adrenocortical tissue. J Am Vet Med Assoc 1986;189:7172.

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  • 4. Marino G, Quartuccio M, Rizzo S, et al. Ectopic adrenal tissue in equine gonads: morphological features. Turk J Vet Anim Sci 2012;36:560565.

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  • 5. Ono H, Satoh H, Miyake M, et al. On the development of “ovarian adrenocortical cell nodules” in the horse. Exp Reprod Equine Health Lab 1969;6:5990.

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  • 6. Okur H, Kucukaydin M, Kazez A, et al. Ectopic adrenal tissue in the inguinal region of children. Pediatr Pathol Lab Med 1995;15:763767.

  • 7. Mendez R, Tellado M, Somoza I, et al. Ectopic adrenal tissue in the spermatic cord in pediatric patients: surgical implications. Int Braz J Urol 2006;32:202207.

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  • 8. Aughey E, Frye FL. Endocrine system. In: Comparative veterinary histology with clinical correlates. London: CRC Press, 2001;156.

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