African hedgehog (Atelerix albiventris).The animal presented for bloody
vulvar discharge, right-sided facial paralysis,
and multiple skin masses. Elective ovariohysterectomy
was performed and multiple
skin masses were removed. A firm multinodular
mass was observed arising from the
internal ear canal. Due to the worsening of
clinical signs, the animal was humanely
euthanized and submitted for postmortem
On necropsy, the animal
was in good body condition. Gross
examination revealed a multilobulated,
white and tan mass measuring 2.5 cm arising
from the right parietal bone and extending
toward the right occipital lobe, surrounding
the external auditory meatus and protruding
through the internal ear canal, as well as
rostrally to the right frontal lobe involving the right turbinates. The cut surface was
yellow, white, and tan, with few white areas
of mineralization. In transverse sections, the
mass focally compressed the cerebral hemispheres,
cranial nerves and partially obliterating the ear meatus. Both lateral
ventricles were moderately dilated.
examination revealed that this mass arises
from the skull, protrudes both internally and
externally, and compresses the brain. The
mass is composed of multiple welldemarcated
nodules, rimmed by a thick
layer of fibrous connective tissue arranged
in sheets of polyhedral to spindle-shaped
cells with large interspersed areas of
coagulative necrosis. Numerous islands and
lakes of osteoid are present throughout the
tumor. The neoplastic cells have abundant
eosinophilic cytoplasm and large, round to
ovoid nuclei with finely stippled chromatin
and often prominent nucleoli. There is marked anisocytosis and anisokaryosis. The
mitotic rate is low, averaging two per ten
400x high powered fields. In some sections,
cranial nerves are markedly compressed by
the neoplasm, with multifocal axonal
swelling and spheroid formation (Wallerian
degeneration). Neurons at this level are
shrunken and hypereosinophilic (necrosis).
Skull: Osteoblastic osteosarcoma, with
cranial nerve compression, Wallerian
degeneration, and neuronal necrosis.
African hedgehogs are common and
represent one of the main causes of disease
in this species. In retrospective studies, the
prevalence of neoplasia has ranged from
29% to 51%. Of these, 85% are malignant,
portending an overall poor prognosis.
Osteosarcomas in this species have been
reported in skeletal and extraskeletal
locations. Skeletal locations include:
ribs,1,6 and vertebra.
extraskeletal sites include the subcutis over
and flank.7 One documented
case of osteosarcoma is theorized to be
associated with retroviral infection.6
Multiple concurrent neoplasms are present
in a small percentage of hedgehogs with
In this case, multiple trichoepitheliomas
and an endometrial stromal
sarcoma were also present.
Although osteosarcoma accounts for up to 85% of malignant bone tumors in dogs and 70% in cats,2 the occurrence in African hedgehogs is unusual. In dogs, osteosarcomas can be subclassified according to the predominant histologic pattern into six different categories: poorly differentiated, osteoblastic, chondroblastic, fibroblastic, teleangiectatic and giant-cell rich osteosarcoma. This classification scheme is an adaptation of a system developed for use in human medicine. Osteoblastic osteosarcoma is the most common subtype, and it can be further sub-classified into nonproductive and productive, based on the tumor bone produced. According to this classification, this osteosarcoma would be classified as a productive osteoblastic osteosarcoma. 2
Additionally, intracranial, extracranial, and skull base neoplasms often compress the facial nerve and may result in facial paralysis.5 In this case, cranial nerve involvement can be seen in some slides. Nerves are clearly compressed and surrounded by the neoplastic tissue, leading to Wallerian degeneration. Wallerian degeneration is a process that occurs when a nerve fiber is cut or crushed, leading to axonal separation from the neuronal cell body which degenerates distal to the injury. 9
Osteosarcoma, African hedgehog, Atelerix
histologic sections of the cranium from this
case spanned from the level of the rostral
diencephalon to the caudal metencephalon.
As a result, conference participants noted
marked slide variation based on the
anatomic location of this neoplasm and its
effects on the adjacent tissue. Due to
extensive variation in tissue sections
submitted, histologic lesions noted by
participants that may not be present on every
slide include: Wallerian degeneration of the
cerebrum and peripheral nerves; compression
of the cerebrum and peripheral
nerves with adjacent neuronal necrosis;
hydrocephalus of the lateral, third, and
fourth ventricles; osteosarcoma (OSA)
tumor emboli within adjacent vessels;
skeletal muscle degeneration, regeneration,
and necrosis; and hyperkeratosis of the
external ear canal.
As mentioned by the contributor, neoplasia is an extremely common antemortem and postmortem finding in the African hedgehog. However, mesenchymal neoplasms, such as in this case, are relatively uncommon with an incidence of only about 4% at necropsy.1,3,8 Epithelial neoplasms of the integument are the most common type, followed by round cell tumors. Osteosarcoma is the most common mesenchymal neoplasm reported in African hedgehogs.3
In dogs and cats, osteosarcoma is characterized by rapid progression and early metastasis to the lungs, resulting in short survival times and high mortality rate.2 This aggressive biologic behavior is similar in reported cases of osteosarcoma in African hedgehogs.1,3,8 The contributor describes six different categories of osteosarcoma in dogs based on the predominant histologic pattern. These include:
1. Poorly differentiated:
- o Variation in cell size from small primitive mesenchymal to large and pleomorphic undifferentiated cells
- o Identification depends on presence of unequivocal tumor osteoid
- o Highly aggressive and associated with pathological fractures.
- o Anaplastic osteoblasts; variable amounts of basophilic cytoplasm, and hyperchromatic, eccentric nuclei
- o Further subclassified as nonproductive or productive based on presence or absence of tumor bone production
- o Productive osteoblastic OSA is the most common subtype in dogs
- o Neoplastic cells produce both chondroid and osteoid matrices
- o Interlacing bundles of spindle cells resembling fibrosarcoma that produce osteoid or bone
- o Solid areas and large bloodfilled spaces lined by malignant osteoblasts that occasionally form spicules of osteoid
- o Resembles hemangiosarcoma, but is immunonegative for factor VIII and CD31
- o Most malignant classification with least favorable prognosis.
- o Tumor giant cells predominate with nuclear atypia and a high mitotic rate
- o Must be differentiated from the benign giant cell tumor of bone2
The conference moderator cautioned participants that histologic classification of osteosarcoma is often complicated by their heterogeneous nature, as several microscopic patterns are often evident within a single neoplasm. Regardless of classification, the prognosis for all subtypes of canine central osteosarcoma is considered poor. The conference moderator also mentioned different grading systems for osteosarcoma based on nuclear pleomorphism, mitotic index, necrosis, multinucleated cells, the amount of tumor matrix, and vascular invasion. Unfortunately, no histologic grading system has gained widespread acceptance by veterinary pathologists due to marked variation in histomorphology of the neoplastic cells within different regions of the same tumor.2
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Girard C, Langlois I. Rib
Osteoblastic Osteosarcoma in an
African Hedgehog (Atelerix
Albiventris). J Vet Diagn Invest.
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3. Heatley J, Mauldin G, Cho D. A Review of Neoplasia in the Captive African Hedgehog (Atelerix albiventris). Semin Avian Exot Pet. 2005; 14:182192.
4. London C, Dubilzeig R, Vail D, Ogilvie G, Hahn K, Brewer W, DVM; Hammer A, O'Keefe D, Chun R, McEntee M, McCaw D, Fox L, Norris A, Klausner J. Evaluation of dogs and cats with tumors of the ear canal: 145 cases (1978-1992). J Am Vet Med Assoc. 1996; 208: 1413-18.
5. Marzo S, Leonetti J, Petruzzelli G. Facial paralysis caused by malignant skull base neoplasms. Neurosurg Focus. 2002; 12 (5): 1-4.
6. Peauroi J, Lowenstine L, Mun R, D. Wilson. Multicentric Skeletal Sarcomas Associated with Probable Retrovirus Particles in Two African Hedgehogs (Atelerix albiventris). Vet Pathol. 1994; 31:481-484.
7. Phair K, Carpenter J, Marrow J, Andrew, G, Bawa. Management of an Extraskeletal Osteosarcoma in an African Hedgehog (Atelerix albiventris). Journal of Exotic Pet Medicine. 2011; 20 (2): 15115.
8. Rhody J, Schiller C. Spinal Osteosarcoma in a Hedgehog with Pedal Self-Mutilation. Vet Clin Exot Anim. 2006; 9: 625631.
9. Zachary JF. Nervous System. In: Zachary JF, McGavin MD, eds. Pathologic Basis of Veterinary 6 Disease. 5th ed. p.p. 959 St. Louis, MO: Elsevier; 2012.