Skin masses, nodules and swellings are a common presentation as they are visible to owners and often worry them. Solid, cystic or oedematous elevations of the skin may be epidermal or dermal, or may extend into the subcutaneous fat and panniculus. All masses and nodules are composed of accumulations of cells, which can be neoplastic, inflammatory, or a mixture of the two. This chapter considers history, clinical examination, differential diagnoses, diagnostic approach, empirical treatment whilst awaiting results, when to refer and what to do if finances are limited. Quick reference guide: Fine-needle aspiration.