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Dear Daisy Dog

My 9-year-old Doberman has several small lumps under her skin. My veterinarian says they should be removed. Can’t a needle biopsy determine if they are cancerous, without having my dog undergo surgery?

Daisy Responds

Skin and subcutaneous (just under the skin) lumps are common in us older dogs. I’ve had a few of my own.

Signs that a mass may be cancerous include: rapid growth of the mass, abnormal skin surface (like bleeding or ulcerated skin), and attachment of the mass to the body underneath the skin. Also, cancer is more frequent in older dogs than younger ones.

Even without these signs, though, a mass can be malignant. The only way to know for sure is to biopsy it, removing all or part of the mass and sending it to the lab, as your veterinarian recommended.

Pathologists there will slice it into thin layers and examine it under a microscope. They’ll look not just at the cells but also at the overall tissue structure, because either can signal cancer.

But you’re also right that a needle inserted into the mass can withdraw some of the cells for examination under a microscope. A fine-needle aspirate (FNA) is not as accurate as a biopsy, but it often gives an indication of the predominant cell type.

Mom did a FNA on one of my lumps and found lots of fat globules without abnormal fat cells. She feels the mass is probably a lipoma, a benign fatty tumor.

On the other hand, she did a FNA on one of my brother’s skin lumps and saw round cells containing purple-black granules. It was a mast cell tumor, a common skin cancer, so she removed it.

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