Congenital mandibular myxosarcoma in a foal

Abstract

A five-week-old Arabian filly presented with a rapidly expanding congenital mass on the rostral portion of the mandible involving the deciduous incisors (#701–703 and 801–802). Radiographs revealed a mass of soft tissue and bone containing a multicameral area of marked osteolysis. On biopsy, the mass contained abundant mucinous fluid; myxosarcoma was diagnosed on clinical, histological and immunohistochemical features. Surgical excision was performed, but excision was incomplete and two months later the tumour recurred rostrally. Rostral hemimandibulectomy was performed, but the foal was euthanased five weeks after discharge because of persistent colic; no tumour recurrence or metastasis was found. Myxomatous tumours are rare in the horse, largely associated with the head and radiographic findings are consistent with a locally invasive mass on the head that appears cystic and osteolytic. While mucin within the mass is highly suggestive, histopathology is required for definitive diagnosis. Complete surgical excision with wide, clean margins is the treatment of choice.

Metastatic cutaneous myxosarcoma in an adult horse

“…1 This tumor belongs to the category of soft tissue sarcomas (STS), originating from mesenchymal cells of connective tissue, sharing clinical behavior and histopathologic aspects with other mesenchymal-origin neoplasms. 2,3 Although rare in equids, myxosarcoma has been reported in horses [4][5][6] and donkeys, 7 but has never been reported in mules and zebras. Therefore, it should be considered as a differential diagnosis when there is the presence of a rapidly growing cyst or mass with local invasiveness and signs of pronounced osteolysis.…”

“…The gold standard treatment in humans involves complete surgical excision of the tumor with safe surgical margins, and adjuvant radiation therapy and chemotherapy can also play a significant role in treating this condition 16 . In horses, excision with safe surgical margins is also recommended, and since radiography may underestimate the tumor's extent, computed tomography can be used to determine the tumor margins before surgery 6 . In contrast, in dogs, radiation treatment has been recommended if there is histologic evidence of incomplete excision 6 .…”

“…16 In horses, excision with safe surgical margins is also recommended, and since radiography may underestimate the tumor's extent, computed tomography can be used to determine the tumor margins before surgery. 6 In contrast, in dogs, radiation treatment has been recommended if there is histologic evidence of incomplete excision. 6 In the present case, surgical treatment was not performed due to the extent of the lesion, the general condition, and the advanced age of the animal.…”

Metastatic myxosarcoma in a Quarter Horse gelding

“…Myxosarcomas are exceedingly rare in equids and have been reported in the gingiva, mandible, and cecum. 3,10,14 Three cases of cecal myxosarcomas have been described previously, all of which metastasized to regional lymph nodes 3,4 ; primary retroperitoneal myxosarcoma with metastasis to thoracic and abdominal viscera has not been reported previously to our knowledge.…”

“…Previous publications document occurrence in the skin, mandible, heart, lungs, and abdominal peritoneum. 1,[5][6][7]14,15 Myxomas and myxosarcomas have been reported to affect both foals and adult horses. Myxomas are rare tumors in equid that have been reported to affect the bone and soft tissues of the head, the heart, and bronchi.…”