What Are Adenomas and Adenocarcinomas in Cats and Dogs

What Are Adenomas and Adenocarcinomas in Cats and Dogs?
Tumors that develop in different parts of the body in cats and dogs are classified according to the cells and tissues from which they originate. Adenomas and adenocarcinomas are among the tumors that primarily arise from glandular tissues or epithelial cells with secretory characteristics.
An adenoma is generally considered a benign tumor, whereas an adenocarcinoma is considered a malignant tumor. However, the distinction between these two tumor types is not limited to their names. The tumor’s biological behavior, relationship with surrounding tissues, growth characteristics, potential for invasion and metastasis, and histopathological features can directly influence the treatment approach.
Therefore, when a new mass is detected in a cat or dog, it is not appropriate to conclude that the mass is “benign” or “cancerous” based solely on its appearance, firmness, or size.

What Is an Adenoma?
An adenoma is a benign tumor that develops from glandular tissue.
Being benign generally means that the tumor is not expected to metastasize to distant parts of the body. However, benign tumors can still grow over time, exert pressure on surrounding tissues, or cause functional problems depending on their anatomical location.
For example, an adenoma developing on the eyelid, in the oral cavity, skin, or other anatomical regions may affect the animal’s daily life depending on its size and location.

What Is an Adenocarcinoma?
An adenocarcinoma is a malignant tumor that develops from glandular tissue or epithelial cells with secretory characteristics.
Adenocarcinomas can occur in different organs in cats and dogs. Examples include the mammary glands, gastrointestinal tract, lungs, and various glandular tissues.
Because adenocarcinomas are malignant tumors, they may invade surrounding tissues and, depending on the tumor type, may metastasize to regional lymph nodes or distant organs. However, not all adenocarcinomas have the same biological behavior.















What Is the Difference Between an Adenoma and an Adenocarcinoma?
The fundamental difference is their biological behavior and malignant potential.
FeatureAdenomaAdenocarcinomaBiological behaviorGenerally benignMalignantInvasion into surrounding tissuesGenerally not expectedMay occurMetastasisGenerally not expectedMay occurGrowthVariableVariableHistopathological evaluationImportantEssential for definitive diagnosis and gradingTreatmentOften surgicalSurgery ± systemic or other treatments
However, these characteristics cannot be reliably determined based solely on the external appearance of a mass. A definitive distinction is often made through histopathological examination. The cellular characteristics, tissue organization, invasion pattern, and, when necessary, molecular or immunohistochemical characteristics of the tumor may be evaluated.

What Are the Signs of Adenocarcinoma in Cats and Dogs?
Clinical signs vary depending on the organ affected and the stage of the disease.
Common findings may include:

• A newly developed or enlarging mass

• Loss of appetite

• Weight loss

• Weakness or decreased energy

• Chronic vomiting

• Chronic diarrhea

• Changes in bowel movements

• Difficulty breathing

• Coughing

• Bleeding

• Enlargement of regional lymph nodes

• Pain

• Impaired organ function

None of these signs alone indicates cancer. However, particularly when symptoms persist, recur, or progressively worsen, veterinary evaluation is recommended.

How Are Adenomas and Adenocarcinomas Diagnosed?
One of the first steps in tumor diagnosis is evaluating the cellular characteristics of the mass.
The following diagnostic methods may be used:

• Fine-needle aspiration

• Cytology

• Biopsy

• Histopathology

• Immunohistochemistry, when indicated

• Ultrasonography

• Radiography

• Computed tomography (CT)

• Other advanced imaging techniques

When a malignant tumor is suspected, staging, which involves determining the extent of tumor spread throughout the body, is critically important for treatment planning.

Is There a Risk of Metastasis in Adenocarcinomas?
Yes. Some adenocarcinomas have a potential for metastasis.
Metastasis occurs when cancer cells detach from the primary tumor and reach other parts of the body through the lymphatic system or bloodstream.
However, the risk of metastasis is not the same for every adenocarcinoma. It may be influenced by several factors, including:

• The organ in which the tumor originates

• Histological tumor type

• Tumor grade

• Tumor size

• Invasion characteristics

• Regional lymph node involvement

• Stage of disease
  

How Is Adenocarcinoma Treatment Planned?
Treatment is individualized according to the tumor type, anatomical location, histopathological characteristics, and stage of disease.
In some patients, surgery may be the primary treatment approach. In other cases, chemotherapy, radiation therapy, or other systemic treatments may be considered in addition to surgery.
Therefore, there is no single treatment protocol that applies to every adenocarcinoma. A treatment plan should be developed specifically for each patient based on the biological characteristics of the tumor and the overall extent of the disease.

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