Pathology Case of the Month - Sandhill Crane

Release Date:

Case History: Approximately 30 sandhill cranes (Antigone canadensis) were found dead during a winter cold snap in Indiana, U.S.A. One bird was noted to have a mass on its leg.

Gross Findings: This adult male sandhill crane was in emaciated body condition and good postmortem condition. On the cranial aspect of the right leg, overlying and distal to the hock, was a 45 x 45 x 35 mm firm, ovoid mass with a mildly roughened black and tan surface (Fig. 1A). On cut section, the mass was gelatinous, contained both firm and soft areas, and was mottled light pink to gray (Fig. 1B). The base of the mass extended to the joint space (Fig. 1B). There were no significant internal abnormalities.

The outside and a cut section of a firm mass on the right cranial hock of a crane with a roughened black and tan surface.

Figure 1. Photographs from a sandhill crane (Antigone canadensis) found dead in Indiana, U.S.A.  (A) There is a firm mass on the right cranial hock with a roughened black and tan surface. (B) On cut section, the mass is gelatinous, mottled light pink to gray, and extends to the joint space (arrow). (Credit: Julia Lankton, National Wildlife Health Center. Public domain.)

Histopathological Findings: The mass is composed of islands of well-differentiated chondrocytes separated by fibrovascular connective tissue containing mixed inflammatory cells. There is mild cellular pleomorphism and no mitotic figures are seen (Fig. 2A). Islands of chondrocytes are multifocally hypereosinophilic (necrotic) and surrounded by granulomatous inflammation (Fig. 2B). There is multifocal hyperkeratosis and focal ulceration of the overlying skin.

Photomicrographs of mass from a sandhill crane

Figure 2. Photomicrographs from a sandhill crane (Antigone canadensis) found dead in Indiana, U.S.A. (A) The mass is composed of islands of well-differentiated chondrocytes separated by fibrovascular connective tissue. There is minimal cellular pleomorphism and no mitotic figures are seen (inset). H&E stain. (B) Multifocally, islands of chondrocytes are hypereosinophilic with loss of nuclear detail (necrosis; asterisk) and surrounded by epithelioid macrophages (arrow). H&E stain. (Credit: Julia Lankton, National Wildlife Health Center. Public domain.)

Morphologic Diagnosis/es:

  1. Mass, hock: Chondroma

Disease: Chondroma (benign neoplasm of cartilage origin)

Etiology: The etiology of chondromas in cranes is unknown, although both traumatic and viral etiologies have been suggested. In domestic chickens, avian leukosis/sarcoma virus can be a cause of chondrosarcomas.

Host range: In birds, chondromas have been reported in both sandhill and whooping cranes (Grus americana), as well as few other captive and free-ranging avian species. Both adult and immature cranes can be affected. Chondromas also occur in mammals, including dogs, cats, cattle, and sheep. 

Clinical signs: In cranes, chondromas are most often reported on the pelvic limbs or plantar surface of the foot. In one case, regression of the remaining mass occurred two years after partial biopsy.

Pathology: Chondromas can arise within the medullary cavity of bone (enchondromas) or can protrude outwards from cartilage (ecchondromas). Grossly, chondromas appear as slow-growing firm to hard spherical masses with a fibrous capsule. On cut section, the surface may have a lobular and/or gelatinous appearance. Microscopically, chondromas are composed of lobules of well-differentiated hyaline cartilage within a fibrous matrix. Differentiation between chondroma and low-grade chondrosarcoma (malignant tumor of cartilage) can be difficult histologically; chondrosarcomas are more likely to be locally invasive.

Wildlife population impacts: Chondromas are rare and typically diagnosed as an incidental finding, although bacterial infection could result if overlying skin is ulcerated. No population impacts are reported.


  • Behera D, Kumar D, Samal A, Panda SK. 2013. Chondroma in an Indian ring neck parrot (Psittacula krameri manillensis): a case report. Vet. World 6(4):223-225.
  • Craig LE, Dittmer KE, Thompson KG. 2016. Chapter 2 - Bones and Joints. In: Jubb, Kennedy & Palmer's Pathology of Domestic Animals: Volume 1 (Sixth Edition), Maxie GM, editor. W.B. Saunders, p. 116.
  • Dittmer KE, French AF, Thompson DJ, Buckle KN, Thompson KG.  2012. Primary bone tumors in birds: a review and description of two new cases. Avian Diseases, 56(2), 422–426.
  • Forrester DJ and Spalding MG. 2003. Parasites and diseases of wild birds in Florida. University Press of Florida, Gainesville, Florida. pp. 1132
  • Hatai H, Tokorozaki K, Haraguchi Y, Matsui T, Ozawa M. 2020. Chondrosarcoma with undifferentiated neoplastic cell proliferation around the distal tibiotarsus bone in a wild Hooded Crane (Grus monacha). J Vet Med Sci. Aug 19;82(8):1093-1096.
  • Miller JL, Spalding MG, Folk MJ. 2010. Leg problems and power line interactions in the Florida resident flock of whooping cranes. In: Proceedings of the Eleventh North American Crane Workshop, Sep 23-27, 2008, Wisconsin Dells, Wisconsin. Hartup BK., editor. North American Crane Working Group, Baraboo, Wisconsin, pp. 156–165.

Related Content

Filter Total Items: 4
Date published: March 1, 2021
Status: Active

Pathology Case of the Month

Notable cases at the National Wildlife Health Center are highlighted here in the Pathology Case of the Month Series.

Date published: July 1, 2019
Status: Active


WHISPers, the Wildlife Health Information Sharing Partnership - event reporting system, is a partner-driven, web-based repository for sharing basic information about historic and ongoing wildlife mortality (death) and/or morbidity (illness) events. The information, such as county-level locations, onset and ending dates, species affected, and...

Contacts: WHISPers Team
Date published: March 29, 2018
Status: Active

Diagnostic Services

The USGS National Wildlife Health Center (NWHC) conducts laboratory investigations to determine the causes of wildlife mortality events, especially large-scale die-offs or those that are otherwise unusual.

Contacts: David S Blehert

Necropsy & Pathology

The Necropsy and Pathology services are performed by board-certified veterinary pathologists and necropsy technical staff whose principal role is to determine the cause of death for animals submitted to the USGS National Wildlife Health Center.