Colonic malignant peripheral nerve sheath tumour in a cat

Abstract

Case summary: A 14-year-old male neutered domestic mediumhair cat presented with a 4 month history of inappetence and weight loss. Pertinent abnormalities on haematology and biochemistry included a mild microcytic regenerative anaemia (packed cell volume [PCV] 24% [reference interval (RI) 30-45%], mean cell volume 30.8 fl [RI 40-45 fl], absolute reticulocyte count 326.8 × 10¹²) and increased alkaline phosphatase activity (76 IU/l; RI <50 IU/l). Abdominal ultrasound and CT scan revealed masses in the transverse colon (2.0 cm × 1.2 cm) and right medial liver lobe (5.0 cm diameter). Thoracic radiographs were unremarkable. Right medial liver lobe resection and colectomy were performed. Immunohistochemistry was positive for S-100 protein, vimentin and glial fibrillary acidic protein, very weakly positive for c-kit and negative for muscle-specific actin and CD18, consistent with a colonic malignant peripheral nerve sheath tumour (MPNST) with a hepatic metastasis. Postoperative treatment with metronomic cyclophosphamide was well tolerated. Eighteen months postoperatively the cat re-presented after 3 days of progressive lethargy and inappetence. Haematology revealed a marked non- or pre-regenerative anaemia (PCV 10%). Coagulation times were prolonged (prothrombin time 39 s [RI 15-22 s] and activated partial thromboplastin time >300 s [RI 65-119 s]). Abdominal ultrasound identified multiple renal and hepatic nodules. Euthanasia was performed and post-mortem examination confirmed metastasis of the MPNST.

Relevance and novel information: This report describes the treatment of a metastatic colonic peripheral nerve sheath tumour in a cat. Feline visceral MPNSTs are rare and little is known about prognosis or optimal treatment.

Keywords: Peripheral nerve sheath tumour; cyclophosphamide; metastasis; metronomic chemotherapy.

Figure 1

Transverse sonogram (Phillips EPIQ5; Phillips Medical Systems) of the right medial liver lobe. There was a large, heterogeneous mass (outlined by callipers) containing a central fluid-filled component

Figure 2

Longitudinal sonogram of the transverse colon. There was an eccentric, intramural hypoechoic mass within the distal portion of the transverse colon. Note the displacement of the intraluminal gas interface by this lesion (arrows)

Figure 3

Colonoscopy revealed a smooth, raised mass in the transverse colon

Figure 4

CT images of the (a) transverse and (b) dorsal planes of the abdomen displayed in a soft tissue window. The patient’s right is to the left. There was a large heterogeneous hepatic mass within the right medial lobe (arrows). Note the heterogeneous post-contrast enhancement of the mass with multiple coalescing non-enhancing regions suggestive of necrosis. Images obtained with a 16-detector row CT scanner (Phillips 16-slice Brilliance CT V2.3; Phillips Medical Systems [120 kVp, 100 mAs, 1.5 mm slice thickness])

Figure 5

CT images of the (a) transverse and (b) dorsal planes of the abdomen displayed in a soft tissue window. The patient’s right is to the left. There is an intramural hypoechoic mass within the transverse colon (arrows). Note the heterogeneous, predominantly peripheral contrast enhancement of the mass.

Figure 6

Intraoperative image of the right medial liver lobe mass (arrow) adjacent to the gall bladder

Figure 7

Colonic mass. Neoplastic cells are arranged in interlacing streams and bundles. Haematoxylin and eosin (× 400)

Figure 8

Hepatic mass. Neoplastic cells demonstrate similar behaviour to the colonic mass (Figure 7). Note the marked anisocytosis and anisokaryosis. Haematoxylin and eosin (× 400)

Figure 9

Colonic mass. Neoplastic cells demonstrate diffuse marked nuclear and cytoplasmic labelling for S-100. Peroxidase immunohistochemistry and haematoxylin and eosin (× 400)

Figure 10

Colonic mass. Neoplastic cells demonstrate diffuse marked cytoplasmic labelling for vimentin. Peroxidase immunohistochemistry and haematoxylin and eosin (× 400)

Figure 11

Hepatic mass. Neoplastic cells demonstrate diffuse marked cytoplasmic labelling for glial fibrillary acidic protein. Peroxidase immunohistochemistry and haematoxylin and eosin (× 400)

Figure 12

Colonic mass. Neoplastic cells demonstrate scattered faintly positive cytoplasmic labelling for c-kit. Peroxidase immunohistochemistry and haematoxylin and eosin (× 400)