Subcutaneous lumps are found under the skin, rather than within the skin or at the surface of the skin. If a lump does not create a visible mark or disruption on the skin, doesn’t arise from the bone, and the skin moves freely over it, it is a subcutaneous lump. Subcutaneous lumps can be anything from a foreign body, parasite, hernia, injury or infection, to a tumor or a cancer such as feline injection site sarcomas.
Many types of subcutaneous lumps are not a threat to overall health, but some are. Diagnostic testing such as aspiration, biopsy, and cytology is necessary to confirm the cause of the subcutaneous lump. Generalizing outcomes is difficult due to the variety of underlying causes.
Subcutaneous lumps in cats are very common. While many subcutaneous lumps are not necessarily cause for concern, some are serious and potentially life-threatening. Diagnostic testing is necessary to determine the specific type of lump, and timely intervention is critical for a good outcome, if the lump proves to be serious.
Subcutaneous lumps have many causes, including:
• Scar tissue • Injuries • Abscesses • Cuterebriasis (a generally harmless parasite)
• Foreign bodies (for example, a microchip, hair follicle, BB pellet, etc)
• Umbilical and inguinal hernias • Tumors, both benign and cancerous
Lipomas (fatty tumors) are an example of a very common benign subcutaneous tumor. Mammary adenocarcinoma (breast cancer) is a common subcutaneous malignancy, particularly in intact female cats and females who experienced at least one heat cycle prior to being spayed. Feline injection site sarcomas (FISS) are a serious concern for subcutaneous masses at injection sites.
There are a wide range of possible causes for a subcutaneous lump on a cat. Some particular types of lumps are more or less likely depending on their location and the age of the cat. The physical appearance of the lump sometimes suggests certain diagnoses, but analysis of the cells within the lump is necessary to confirm a diagnosis. Treatment varies depending on the diagnosis. Some subcutaneous lumps are harmless when left in place and some must be removed. In some cases, outcomes are more severe such as with fibrosarcoma.
Common diagnostic approaches include:
• Aspiration (the use of a needle to non-invasively draw out material from inside the subcutaneous lump for testing)
• Cytology (the microscopic investigation of the material to determine its structure, function and pathology)
Treatment is dependent on diagnosis.
Subcutaneous lumps may be mistaken for:
• Cutaneous lumps (distinguished from subcutaneous lumps by the fact that they mark or disrupt the surface of the skin)
• Tumors arising from the bone
A variety of symptoms occur depending on the cause of the subcutaneous lump. If the lump is associated with an underlying condition, the symptoms of that condition are expected to develop. If the lump is benign, there may be no additional symptoms other than the lump itself.
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