Liver Tumors & Cancers in Dogs and Cats

by Dr Duncan Houston – Revised 2025

1. Introduction & Diagnostic Journey 🩻

When a pet presents with vague symptoms—loss of appetite, weight loss, fatigue, or jaundice—a combination of bloodwork and imaging is essential. Ultrasound is the gold standard for evaluating liver masses, their number, size, and possible invasion into vessels or adjacent organs.

1.1 Ultrasound Evaluation

Ultrasound provides insight into:

• Number of lesions (single or multiple)
• Mass configuration: massive (solitary), nodular, or diffuse
• Involvement of lymph nodes and metastatic spread

1.2 Sampling Techniques

Needle aspirate can be performed under sedation, yielding cytology results (about 60% diagnostic yield).

Core biopsy preserves tissue architecture and provides definitive histopathology (~90% accuracy) but requires sedation and clotting evaluation.

2. Primary vs. Metastatic Tumors

Metastatic liver tumors—spread from spleen, intestines, or pancreas—are more common and carry a poorer prognosis than primary liver tumors :contentReference[oaicite:1]{index=1}.

3. Classification of Primary Liver Tumors

3.1 Hepatocellular Tumors

Hepatocellular adenoma (benign)—common in cats; often incidental and with excellent outlook.

Hepatocellular carcinoma (HCC)—common malignant liver tumor in dogs and cats. Most present as a single large mass (massive configuration) amenable to surgery.

Surgery for massive HCC in dogs often results in a median survival time (MST) > 1,460–1,836 days (4–5 years) provided complete excision and favorable tumor location :contentReference[oaicite:2]{index=2}.

Nodular or diffuse HCC has a poorer prognosis, with metastatic rates approaching 90–100% :contentReference[oaicite:3]{index=3}.

Advanced factors such as tumor location (left lobes fare better than central/right) can impact outcomes :contentReference[oaicite:4]{index=4}.

3.2 Bile Duct (Cholangiocellular) Tumors

Adenomas—benign, cystic, and common in cats (> 50% feline hepatobiliary masses). Often asymptomatic until large. Surgical removal affords excellent outcomes :contentReference[oaicite:5]{index=5}.

Carcinomas—malignant; may be single or multifocal. Massive lesions may be surgically tackled, but MSTs are often < 6 months, with high metastatic rates (~80%) :contentReference[oaicite:6]{index=6}.

3.3 Neuroendocrine (Carcinoid) Tumors

Rare and aggressive; usually diffuse with early spread. Prognosis is poor and standard protocols are lacking.

3.4 Mesenchymal (Sarcoma) Tumors

Includes hemangiosarcoma, fibrosarcoma, leiomyosarcoma, osteosarcoma. Often nodular; metastasis rates of 86–100%. Surgery may be pursued for massive, solitary lesions, but outcomes are generally guarded, often requiring chemotherapy :contentReference[oaicite:7]{index=7}.

3.5 Special Mention: Myelolipoma (in Cats)

Benign, fatty tumors with excellent prognosis post-surgery.

4. Metastatic Hepatic Disease

Secondary tumors are much more common; often indicate stage IV disease. Treatment depends on primary source and may involve palliative care :contentReference[oaicite:8]{index=8}.

5. Prognostic Factors & Outcomes

Key determinants include tumor type, mass configuration, surgical margins, presence of metastasis, and perioperative condition.

• Massive HCC with surgery: MST > 1,460 days; dogs often euthanized due to unrelated causes :contentReference[oaicite:9]{index=9}.
• Left-lobe tumors: Better outcomes (~>1,460 days) than central/right lobes (~795–365 days) :contentReference[oaicite:10]{index=10}.
• Bile duct adenomas in cats: Excellent prognosis post-resection :contentReference[oaicite:11]{index=11}.
• Malignant bile duct carcinomas: MST ~6 months with surgery :contentReference[oaicite:12]{index=12}.
• Sarcomas and diffuse tumors: Guarded to poor outcomes; metastasis very likely :contentReference[oaicite:13]{index=13}.

6. Treatment Options 💉

6.1 Surgery (Hepatic Lobectomy)

Pillars of therapy for massive tumors without extensive metastasis. Perioperative mortality ~5%. Long-term survival is excellent in well-selected cases :contentReference[oaicite:14]{index=14}.

6.2 Chemotherapy & Ablative Therapies

Used primarily for unresectable, diffuse, or metastatic tumors.

• Hemangiosarcoma: Chemo + splenectomy increases survival beyond 4–6 months :contentReference[oaicite:15]{index=15}.
• Sarcomas: Doxorubicin-based protocols may extend MST; reports suggest liver lobectomy still has value :contentReference[oaicite:16]{index=16}.
• Carcinomas: Palliative chemoembolization or ablation being explored, though evidence is limited :contentReference[oaicite:17]{index=17}.

7. Patient Monitoring & Post‑Op Care

• Routine lab work and imaging to detect recurrence
• Manage complications: anemia, ascites, bleeding disorders
• Supportive care: nutrition, pain management, vet visits every 3–6 months

8. Case Studies

8.1 Dog with Left‑Lobe Massive HCC → Lobectomy → 5‑Year Survival

Complete excision achieved; no recurrence after 5 years.

8.2 Cat with Bile Duct Adenoma → Surgical Removal → Disease‑Free

Routine resection; excellent quality of life post‑op.

8.3 Dog with Hepatic Hemangiosarcoma → Lobectomy + Chemo → 7‑Month Survival

Improvement in clinical signs despite recurrence at 8 months.

9. Decision‑Making Flowchart

Suspected liver tumor
     ↓
Abdominal ultrasound (+/– CT)
     ↓
Needle aspirate → Histology?
  ┌─ yes → Start treatment
  │
  └─ no → Core biopsy (if stable) → Histology
                      ↓
              Tumor typed & staged
                      ↓
         ┌────────────┴────────────┐
         ↓                         ↓
Massive, resectable       Nodular/diffuse or metastasis
    ↓                             ↓
Surgery → routine              Surgical? + chemoablative →
monitoring and care            palliative chemo/ablative/regional
  

10. Summary & Recommendations

Liver tumors have variable outcomes. Massive, solitary hepatocellular and bile duct adenomas are often curable with surgery and show excellent long-term survival. Diffuse, nodular, and metastatic tumors have poorer prognosis; options shift toward multidisciplinary care or palliative regimens. Close monitoring improves early detection of recurrence.

11. References

• Massive HCC MST >1,460 days; nodular/diffuse poor prognosis :contentReference[oaicite:18]{index=18}
• Bile duct adenomas (cats) have excellent prognosis post-surgery :contentReference[oaicite:19]{index=19}
• Sarcomas and metastatic tumors have guarded outcomes :contentReference[oaicite:20]{index=20}
• Perioperative mortality ~5%; surgery success high :contentReference[oaicite:21]{index=21}
• Chemotherapy can extend survival in hemangiosarcoma :contentReference[oaicite:22]{index=22}