Case 170317-3

Ten-year-old, castrated, male cat (Persian)

This animal was presented to the referring veterinarian for a 1.5-cm-diameter, cylindrical nasal swelling on the bridge of the nose for at least seven months. A fine-needle aspirate of the mass was inconclusive and the animal was referred for further assessment. A CT scan revealed that while the mass effaced the normal soft tissues of the rostro-dorsal aspect nasal bridge there was no evidence of invasion into the nasal cavity, osteolysis of the nasal bones or turbinate destruction. A punch biopsy of the mass was submitted for histopathology.

No gross description was provided.

One section of haired skin is examined in which the dermis is greatly expanded by a cellular mass of spindle-cells that extends to the dermo-epidermal junction and surrounds and separates adnexal structures. The neoplastic cells form interlacing streams and bundle and are supported by moderate amounts of collagen. They have indistinct cell borders, a moderate amount of pale eosinophilic cytoplasm, and an ovoid, elongate nucleus. The chromatin is finely stippled and nuclei typically contain one variably distinct basophilic nucleolus. Anisocytosis and anisokaryosis are moderate, and there is one mitotic figure per ten 400x fields. Skeletal muscle fibers are separated and individualized by the infiltrating population. lymphocytes, plasma cells, neutrophils, eosinophils, and mast cells are scattered throughout the spindle cell population but they are most prominent in the superficial aspect of dermis.

No special stains.

Haired skin, nasal bridge: Spindle cell tumor

Based on the morphology of the cells and their architectural arrangement, the sample is most consistent with a spindle cell tumor. Top differentials include a feline sarcoid or a fibrosarcoma. Based on the architectural arrangement of the cells extending to the epidermis, as well as the anatomical location of the mass and that it is mostly affecting the skin, a feline sarcoid is the most likely differential.

Feline sarcoids are rare mesenchymal neoplasms which most commonly develop around the face and digits of younger domestic cats. The same papilloma virus DNA sequence, designated the feline sarcoid-associated PV sequence, has been consistently detected in multiple studies of sarcoids from domestic cats and exotic felids. This sequence is not found in non-sarcoid cat tissues. It has been suggested that feline sarcoids are caused by cross-species infection by a bovine papilloma virus (BPV-14). Conference participants mentioned that a correlation has been made between feline sarcoids and feline exposure to cattle. It was discussed that while this may be true in some cases, cases have been seen where there is no exposure of the cat to any bovine.

Other differentials were suggested such as a leiomyosarcoma and a type of fibrosarcoma which commonly occurs in the facial region of cats.

Munday JS, Thomson N, et al. Genomic characterization of the feline sarcoid-associated papillomavirus and proposed classification as Bos taurus papillomavirus type 14. Veterinary Microbiology. 177 (3-4): 289-95.