UNUSUAL TUMORS IN SEA OTTERS
(NOTE: THIS PAGE IS STILL UNDER CONSTRUCTION!)
FLASH!
On February 17th we necropsied another hunter-killed sea otter that had a huge lump on its side. Although not as big as the first one, described on this page, this tumor looks like it will be a sarcoma of some kind. It was a 5.9 kg tumor from a sea otter with a skinned carcass weight of 30.5 kg.FEBRUARY 26TH: PICTURES HAVE BEEN POSTED. SEE BELOW.
We do necropsies opportunistically on sea otters that are found dead on the beach (if they are fresh!) and on animals shot by native subsistence hunters, if there seems to be something wrong. In 1995, subsistence hunters submitted two sea otters because they noticed large lumps on the animals.
A chondrosarcoma weighing 7.7 kg was found in a sea otter weighing 23.6 kg (skinned carcass). The costochondral junction was the apparent source of the tumor, which filled most of the thoracic cavity. A narrow space remained dorsally in the thorax, allowing limited expansion of the lungs. While the animal was in poor body condition, food was present in its stomach when it was killed, indicating that the sea otter was still able to dive and forage for food. A spindle cell tumor, probably a malignant schwannoma with osseous metaplasia, was found on the hindlimb of a second sea otter.
Reports of neoplasms in the sea otter have been sparse, considering the attention this species has received because of the classification of the Southern sea otter as endangered, and the large numbers of carcasses examined following the Exxon Valdez oil spill. Leiomyomas have been found in several sea otters, including in one animal with concurrent liver adenocarcinoma and pheochromocytoma. A 4 cm uterine tumor, judged to be a leiomyoma by its gross appearance, was found during analysis of female reproductive tracts taken from sea otters killed by the Exxon Valdez, but microscopic examination was not done because of the state of autolysis of the tissues.
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At left, I am holding up the huge chondrosarcoma that was removed from the sea otter carcass laying on the necropsy table in front of me. The sea otter had some food in its stomach, indicating that it was managing to continue feeding. Its poor body condition indicated that its food intake was insufficient.
Below, the tumor is viewed in situ in a posterior-anterior view of the chest, with the left rib cage reflected laterally. The sea otter is in dorsal recumbency. The tumor almost filled the thorax, leaving space dorsally about 5 to 7 cm, in which lay the heart and lungs. It is difficult to conceive how this animal managed to ventilate sufficiently to dive and search for food. |
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The external part of the mass (visible at the top of the ruler) measured about 20 cm long, 15 cm wide, and 5 cm deep. The internal portion measured about 33 cm long by 30.5 cm wide and 16 cm deep. |
PICTURES OF THE LATEST TUMOR!
The Alaska Sea Otter Commission (ASOC), the US Fish and Wildlife Service (USFWS), and the Biological Resources Division of the US Geological Survey (USGS/BRD) are cooperating in a biosampling program to obtain samples and information from native hunters of sea otters.
Hunters shot a sea otter with a large lump on its side by near the north end of Khantaak Island. On February 17th 1998, we necropsied the skinned carcass. There was a mass on the right side of the abdomen. The mass measured 24 by 20 cm and weighed 5.9 kg (13 pounds). The sea otter was an adult male that was 131 cm long and weighed (skinned carcass) 30.5 kg (67 pounds). The animal was in slightly poorer body condition than we would consider normal.
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ç This is the carcass as we received it. It had been frozen and thawed. The mass is the yellowish-colored object on the side of the animal. In texture it was slightly fluctuant.
ç Dr. Kathy Burek (holding tissue) takes a sample. Others in the picture are (clockwise from bottom, left): Kim Williams, ASOC, Angela Doroff, USFWS, Dr. Linda Comerci, USFWS, Robin Samuelson, ASOC student intern, Carol Gorbics, USFWS, Dr. Burek, and Barbara Bodner (ASOC). |
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Once the carcass had been opened, the full size of the spherical mass could be seen. Unlike the previous chondrosarcoma, this tumor did not extend into the thorax. It was covered in peritoneum and was therefore retroperitoneal. The source of the tumor was the 14th rib, although dissolution of the ribs made the exact origin difficult to ascertain. |
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The extracted tumor is shown here held by Barbara Bodner, ASOC (left) and Angela Doroff, USFWS (right). Kim Williams (ASOC) is shown in the background. |
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Here is the tumor, sectioned to show in internal structure. A large portion of the tumor was necrotic (the dark red and brown areas on the cut surfaces). Pieces of the tumor are being examined histologically by Dr. Kathy Burek, a veterinary pathologist in private practice. I will post details of her report when I receive it. Several large pieces of the mass were frozen for a possible virus scan. |
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