Page 205 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

VetBooks.ir 11 Metastatic Lesions

General information
Skin metastases of non-primary skin tumours are extremely rare in dogs and cats and only spora-
dic cases have been reported in the literature. In certain cases, cutaneous metastases may be the
first sign of an undiagnosed non-cutaneous malignancy. An accurate search for a primary dis-
ease, knowledge of any previous history of neoplasia and the awareness of certain established
tumour patterns of metastases (e.g. metastatic bronchial carcinoma to the digits in cats) are
crucial to help in establishing the nature of the metastatic process, as cytology alone may not be
sufficient. Cutaneous metastases have been reported for the following neoplasms:

• Epithelial tumours:
• Gastrointestinal carcinoma (dogs, cats).
• Renal carcinoma (dogs).
• Transitional cell carcinoma (dogs).
• Pulmonary carcinoma (including the lung–digit syndrome of cats).
• Mammary carcinoma (including inflammatory mammary carcinoma in dogs).
• Neuroendocrine carcinoma of nasal origin (dogs).
• Mesenchymal tumours:
• Haemangiosarcoma (dogs).
• Rhabdomyosarcoma (dogs).
• Osteosarcoma (dogs).
• Round cell tumours:
• Visceral mast cell tumour (dogs and cats).
• Multiple myeloma (dogs).
• Transmissible venereal tumour (dogs).
• Sex cord stromal tumours:
• Seminoma (dogs).
• Leydig cell tumour (dogs).
Lymphoma and histiocytic neoplasms arising from other organs may also secondarily involve
the skin, as progression of a generalized disease.
Cytological features
• The cytological features of the tumours listed above are typical of the primary neoplasm. The
reader should refer to specific cytology textbooks for detailed morphological descriptions.

192 © Francesco Cian and Paola Monti 2019. Differential Diagnosis in Small Animal Cytology
(F. Cian and P. Monti)