Melanocytic tumours of the nasal planum in cats: 10 cases (2004-2019).

Abstract

To better characterise signalment, biologic behaviour, and treatment outcome in melanocytic tumours of the nasal planum in cats. Retrospective study in cats diagnosed with histopathologically confirmed melanocytic tumours on the nasal planum. Ten cats were identified with melanocytic tumours of the nasal planum. Pigmentation of the nasal planum seemed to be a predisposing factor. Seven cats were diagnosed histopathologically with a malignant melanoma, three with a benign melanocytoma. One of the cats developed a lymph node metastasis despite diagnosis of a well-differentiated melanocytic neoplasia. In four cases, a pigmented mass, which was initially stable over a long time, showed a sudden rapid progression suggesting malignant transformation. Treatments included hypofractionated radiation therapy (n=6) and surgical resection (n=1). In three cats no further treatment was pursued. Complete (n=3) and partial (n=3) remissions were observed in cats treated with radiation therapy; however, all experienced tumour progression or recurrence after a short period of time. Most of the cats (n=7) had to be euthanased due to tumour progression (median survival time: 265 days). The present case series provides insights in clinical presentation and clinical outcomes of cats with melanocytic tumours of the nasal planum.