Cutaneous Histiocytoma (Langerhans’ cell tumour)

A histiocytoma

A histiocytoma is a benign skin tumour frequently seen in many breeds of dog, including the flatcoated retriever. They are more commonly seen in young dogs under three years old, often on the edges of the ear pinna, the lips, neck and limbs.

Many of you may have seen these solitary lumps on your own dogs where they can appear very quickly and are typically raised, ulcerated and hairless. You usually only see one of them at a time.

Most histiocytomas regress spontaneously over a six week period but they can often be scratched at by the dog or they may start to bleed after being accidentally knocked against something. Because they are ulcerated they can feel moist to touch and when the dog is lying on its bedding it can stick to it.

The tumours are made up of Langerhans’ cells which are a special type of immune cell seen in the lower level of the skin epidermis. The tumours are benign but the trouble is that they can look very similar in appearance to some types of mast cell tumour (these tumours have the potential to cause far more problems as they are malignant). For this reason it is a good idea to have any suspicious skin masses examined by your vet, who may recommend surgical removal to give you peace of mind.

If your vet does decide to remove it he/she may remove quite a large margin just in case it turns out not to be benign. Another option available is to perform a fine needle aspirate biopsy (FNA) to look for Langerhans’ cells but this may not always be diagnostic and excision may still later prove necessary.