Pleomorphic adenoma excision wound in a 47 year old female patient. Pleomorphic ademoma is a type of benign (harmless) tumour and the most common type of salivary gland tumour (here, the parotid gland). Behind the patient's ear, a seroma (pocket of clear serous liquid) can be seen starting to form. After surgery, seromas can develop in the previously excised area due to an accumulation of body fluid or saliva.