Signalment:  

Four-year-old, female, Labrador retriever, canine (Canis familiaris)The patient was presented for a routine ovariohysterectomy.

Gross Description:  

The ovary was gray and shriveled.

Morphologic Diagnosis:  

Ovarian ganglioneuroma

Condition:  

Teratoma

Contributor Comment:  

Neoplasms and hyperplasias of ganglionated plexuses outside the central nervous system are called ganglioneuromas and ganglioneuromatosis, respectively.(1-4) These lesions are rare and have been reported in a steer (2), a horse (1), a cat, and dogs.(3,4) They are composed of variably sized neurons, nerve fibers, and connective tissue stroma. Ganglioneuromas tend be solitary, unencapsulated but well demarcated masses. Mitotic figures are rare or absent. There are no reports of metastasis.(4) Ganglioneuromatoses tend to segmental, infiltrative and involve all layers of the intestine.(2) In human beings, ganglioneuromatosis has been associated with multiple endocrine neoplasia.

Diagnosis can be confirmed by a variety of methods to include transmission electronmicroscopy (TEM), histochemistry, and immunohistohemistry. TEM reveals dense core vesicles in ganglion cells and neuronal processes. Umyelinated axons are encased by Schwann cells. Histochemical stains for axons and myelin reveal that nerve fibers are nonmyelinated. Immunohistochemical stains revel that ganglion cells are positive for NSE and Schwann cells are positive for S-100 and vimentin. Nerve fibers are positive for neurofilament protein.(4)

Neurogenic tumors of the canine ovary have not been described. The nerve supply to the ovary is via a sympathetic plexus that accompanies the ovarian vessels. This relationship may explain the numerous small vessels enmeshed in the tumor.

JPC Diagnosis:  

Ovary: Teratoma, favor monodermal variant

Conference Comment:  

Our differential diagnosis for this neoplasm included ganglioneuroma and central nervous tissue component of teratoma. Ganglioneuromas consist of large ganglion cells separated by fusiform Schwann cells and collagen. The neurons in the present case were separated by a felt-like background of cellular processes resembling neuropil; this neuropil also contained cells resembling oligodendrocytes and astrocytes. We interpret this as central nervous tissue differentiation rather than peripheral nervous tissue differentiation, and therefore the neoplasm is consistent with the central nervous tissue component of teratoma. Differentiation along other embryonic cell layers is not evident in the sections examined during conference. Examination of other regions of the tumor is needed to confirm that differentiation along other embryonic layers is not present. Pathologists from the AFIP Departments of Gynecologic and Breast Pathology, Neuropathology, and Soft Tissue Pathology concurred with the diagnosis. 

Although teratomas are usually defined as neoplasms composed of tissue derived from at least two germinal layers (6), occasional ovarian tumors may be composed of cells from only one layer. In humans, these tumors are derived predominately or exclusively of endodermal or ectodermal tissue and are referred to as monodermal teratomas.(7) Rarely these neoplasms are composed almost exclusively of neuroectodermal tissue, including astrocytes, oligodendroglial cells, and ganglion cells.(7) Arguably such tumors may be hamartomas rather than true neoplasms. 

References:

1. Allen D, Swayne D, Belknap JK: Ganglioneuroma as a cause of small intestinal obstruction in the horse: A case report. Cornell Vet 79:133-141, 1989
2. Cole DE, Migaki,G, Leipold HW: Colonic ganglioneuromatosis in a steer. Vet Pathol 27:461-462, 1990
3. Fairley, McEntee MF: Colorectal ganglioneuromatosis in a young female dog (Lhasa Apso). Vet Pathol 27:206-207, 1990
4. Ribas JL, Kwapien RP, Pope ER: Immunohistochemistry and ultrastructure of intestinal ganglioneuroma in a dog. Vet Pathol 27:376-379, 1990
5. Schlafer DH, Miller RB: Female genital system. In: Jubb, Kennedy, and Palmer's Pathology of Domestic Animals, vol 3 ed. Maxie MG, pp. 450-456. Elsevier Limited, Philadelphia, PA, 2007
6. MacLachlan NJ, Kennedy PC: Tumors of the genital systems. In: Tumors in Domestic Animals, ed. DJ Meuten, 4th ed., p. 554. Blackwell, Ames, IA, 2002
7. Scully RE, Young RH, Clement PB: Monodermal Teratomas. In: Atlas of Tumor Pathology, Tumors of the Ovary, Maldeveloped Gonads, Fallopian Tube, and Broad Ligament, ed. J Rosai, Third series, Fascicle 23, pp. 285-306, Armed Forces Institute of Pathology, Washington, DC, 1996

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4-1. Ovary, dog.

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