Читать книгу Veterinary Surgical Oncology - Группа авторов - Страница 152

PNSTs include a variety of neoplasms including (malignant) schwannoma, neurofibroma, and neurofibrosarcoma. Reported incidence is 0.5–2% of all skin tumors in dogs (Goldschmidt and Shofer 1992; Kaldrymidou et al. 2002; Pakhrin et al. 2007), although reported data vary considerably, depending on varying classification of these tumors. They are locally aggressive and metastasize rarely (<20% in dogs). These tumors arise from peripheral nerves, resulting in locally infiltrative neoplasia in skin and subcutaneous tissue.

PNST can also arise in a nerve plexus and in nerve roots, which can result in compression of nerves resulting in unilateral lameness, muscle atrophy, pain, and paresis (Brehm et al. 1995; Harcourt‐Brown et al. 2009). One case report describes a concomitant malignant PNST and benign cutaneous PNST in a 10‐year‐old cocker spaniel causing respiratory impairment (Silva et al. 2017). In dogs, they arise in the subcutaneous tissues of the extremities most commonly.

If they appear in the region of the spinal canal, they frequently cause painful nerve compression and neurologic deficits, but in more distant locations pain is often absent. Spinal nerves of the brachial plexus (C6–T2) and nerve roots are the most common sites for proximal PNSTs in dogs (Anderson et al. 1999; Essman et al. 2002; Kim et al. 2003; Patterson et al. 2008; Sugiyama et al. 2008).

Electrophysiology may define the location of peripheral nerve involvement.

A CT scan or MRI of the tumor region is strongly advised before surgery to evaluate the extension of tumor involvement and surgical possibilities.

Malignant lesions are more often positive for S‐100 and present a proliferation index significantly higher compared to the benign lesions (Teixeira et al. 2016).

In general, the prognosis for dogs with proximally (centrally) located PNSTs is poor, and the recurrence rate after surgery is high. Survival times up to 27 months after surgical intervention have been reported but usually are much shorter (Bagley et al. 1998; De Queiroz et al. 2008; LeCouteur 2001; Sawamoto et al. 1999). Distally located PNSTs have a much more favorable prognosis. Tumor recurrence after surgery (resection type not specified) was 20% in one retrospective study and occurred for both histologically benign and malignant tumors (Schulman et al. 2009). Distant metastasis was not seen.

Treatment of MRI‐Diagnosed Trigeminal PNSTs by stereotactic radiotherapy (3 dose fractions of 8 Gy on consecutive days or every other day to a total of 24 Gy) in 6 dogs resulted in a disease‐specific survival of 745 days (99–1375 days) (Hansen et al. 2016).

In cats, PNSTs are rare. They mostly arise in the dermis or subcutis of the head, neck, or limbs (Schulman et al. 2009). They are underestimated relative to the more common spindle cell tumors of soft tissue. A constant concurrent expression of vimentin, NSE, and laminin might confirm the diagnosis of PNST in the absence of clear S‐100 protein positivity, especially in the malignant forms (Mandara et al. 2013).