The Little Lump With a Big Lesson: Understanding Histiocytomas in Dogs

Some years ago, we treated a memorable case involving Godzilla, an adorable six-month-old Bulldog pup who developed a peculiar skin growth behind his left foreleg. The lump was button-shaped, hairless, and ulcerated — enough to worry any pet parent.

Why We Can’t Diagnose Lumps Just by Looking

When it comes to skin growths, even experienced vets cannot diagnose a lump purely by sight or touch. Many different conditions look similar on the surface.

In Godzilla’s case, I performed a fine-needle aspirate, using a small needle and syringe to collect cells from the mass. After staining the sample and examining it under a microscope, I was able to make a diagnosis. (If this test is inconclusive, we send samples to a laboratory for further analysis.)

The Diagnosis: Histiocytoma

Godzilla’s lump turned out to be a histiocytoma — a benign skin tumour. These do not spread to other areas and usually do not cause serious harm.

Histiocytomas are:

• Common in young dogs under two years old 
• Reported more frequently in Bulldogs, Boxers, Bull Terriers, Cocker Spaniels, and Great Danes 
• But in reality, they can occur in almost any breed 

Do Histiocytomas Go Away on Their Own?

Most histiocytomas resolve naturally within 2–3 months. However, removal is recommended if they:

• Become infected 
• Grow large 
• Cause discomfort or irritation 
• Show features suspicious for the rare malignant form (Malignant Fibrous Histiocytoma) 

In these cases, the growth is surgically removed and often sent to a specialist pathologist for confirmation.

A Reminder to All Pet Parents

Always have any new lump or bump examined by your vet. It is not possible to determine exactly what a mass is simply by looking or feeling it.

What Happened to Godzilla?

Godzilla’s histiocytoma needed to be removed — and we’re pleased to share that he made an excellent recovery. Thank you to Ashley Liu (Godzilla’s mom) for the beautiful collage of his journey.

Till next time,
Dr Larry
Bruma Lake Veterinary Clinic