Firstly, if you have found a lump, try not to panic. It can be worrying when you discover a lump or sign of illness on a much-treasured pet; but we will discuss lumps in rats and why it’s not always as bad as it might first appear. However, we would always advise you to seek your vet’s advice if you notice a new lump suddenly appears. 

Rats are prone to various types of lumps, which can be growths or swellings, They may appear suddenly or slowly grow over time and can be located anywhere in the skin. It is important to check your pet regularly for any lumps. It may also be useful to note down any other changes in the rat’s behaviour or day to day routine that may coincide with the lump appearing.This might include a change of appetite, demeanour or any signs of sickness, as your vet may ask you about these.  

Types of lumps

Some of the main lumps that rats can develop are swellings from injuries or infection (abscess), they can get fatty growths (lipoma) and also mammary lumps. These can be categorized as either a non-harmful growth (benign) or a nasty growth that can spread in the body (malignant). If they are non-harmful, they can still grow to be very large and depending on the location may cause problems walking or eating for example. The more harmful types of lumps may spread to other areas of skin or spread internally, causing other symptoms or problems.

Infection & Swellings 

These can be caused by fighting between groups of rats or an injury from an object in the environment and can vary in size. They will often feel soft and can be painful, so we advise you to be gentle when handling your rat. In addition, it may be worth checking the housing for any sharp or damaged areas that could have caused an injury. An infection often needs treatment to help it resolve fully so we would advise seeking your vet’s advice.

Fatty tissue (Lipoma)

These are generally soft and often move around when felt and they do not tend to bother them. They are not painful but may cause discomfort if they press on a leg when walking. It can be hard to tell if a lump is made of fatty tissue or not by simply looking at it. 

Mammary (breast tissue) lump

These are the most common type of lump seen in rats and can appear in both males and females. They can appear in young rats also and are often mistaken for other lumps as they can actually be found over a wide area of the body from the neck down the length of the body underneath, due to the large amount of mammary tissue. They are not painful and are mostly a non-harmful type (fibroadenoma) but can grow very large, with a very small percentage of them being a nasty type. It is not uncommon for rats to get multiple lumps of this type over time.  

Can I leave it alone? 

To answer this question, we need to determine what type of lump is present and for this an examination and sometimes a biopsy is needed, which usually involves an anaesthetic. Once it is determined what type of lump it is then more information can be given as to whether surgery or another treatment is required. 

So, to answer the question of will the lump go away, we would advise you seek your vet’s advice on the next step, if a small swelling due to trauma is diagnosed this may well go on its own.