Ferret Chordoma

HISTORY

Middle aged to older ferret with large swelling/mass on tail. FNAB were initially performed (see Fig 1) with follow up histology (see Fig 2 and 3)

Figure 1: FNAB of tail mass - Small aggregates of highly vacuolated polygonal cells (physaliferous cells) in a background of blood. Anisocytosis and anisokaryosis are moderate to marked. 200x Wright-Giemsa
Figure 2: Histology of tail mass – A large multilobular neoplasm is present and composed of plump polygonal cells which have a moderate to large amount of pale eosinophilic, slightly granular cytoplasm which is often expanded by clear, well delineated cytoplasmic vacuoles (physaliferous cells). A small amount of pale mucinous/myxomatous matrix is often observed within lobules of neoplastic cells. Foci of remnant bone and cartilage of the coccygeal vertebrae are observed within the mass. 40x H&E
Figure 3: Histology of tail mass – Higher magnification of Figure 2 showing finer detail of the physaliferous cells. Compare with the cells noted on cytology (Fig 1). 200x H&E.

DIAGNOSIS

Chordoma

COMMENT

Chordomas are rare, slow growing neoplasms derived from embryologic remnants of notochord. During foetal development the notochord is replaced by the developing vertebral column, but small remnants remain in the nucleus pulposus of the intervertebral disc. Rests of notochord outside of the intervertebral discs also occur and it is from these which chordomas are thought to develop. While not specific to ferrets, these animals seem to present most commonly with these neoplasms. These masses occur along the axial skeleton but, as in this animal, the distal tail is the most common location for mass development in ferrets. Due to the slow development of the neoplasms early excision is often curative. For those neoplasms along the distal tail complete excision is easily achievable. Masses in other areas along the axial skeleton (e.g. cervical spine) are often less amenable to complete excision and in these cases recurrence is possible. If left unimpeded, metastases can develop in a small subset of cases. In ferrets, this thankfully appears to be a slow process often taking years before clinically apparent metastases are discernible.

References:

Cho et al. Chordoma in the tail of a ferret. Lab Anim Res. 2011.27(1):53-7
Frolich and Donovan. Cervical chordoma in a domestic ferret (Mustela putorius furo) with pulmonary metastasis. JVDI. 2015, Vol. 27(5) 656–659.