Oncology Principles PDF

Oncology 21 CH A P TE R Patricia A. Schenck...

Oncology 21 CH A P TE R Patricia A. Schenck B. Radiotherapy ONCOLOGY PRINCIPLES 1. Used for local or regional tumors I. Presentation 2. Can be used before surgery to reduce the size A. Pay particular attention to the age, sex, breed, of the tumor, concurrently with chemotherapy, and species, as this information often helps with or postoperatively the diagnosis 3. The effectiveness of radiation therapy can B. The location of the tumor, the duration, and be improved by chemotherapy-induced growth rate are also important radiosensitization C. A complete physical examination is necessary to 4. Need to irradiate potentially affected tissues assess the overall health of the animal. Regional and a normal tissue margin lymph nodes should be carefully palpated and 5. Frequent small doses of radiation allow for repair the lungs assessed of normal cells and decreased radiation toxicity II. Diagnosis 6. Radiation is most effective when the tumor A. Laboratory evaluation size is small 1. A complete blood cell count (CBC), serum C. Chemotherapy biochemistry profile, and urinalysis should be 1. Most often used for regional or disseminated performed to assess overall health neoplasms 2. Other laboratory tests are performed as 2. Some tumors are quite chemosensitive needed (e.g., feline leukemia virus [FeLV], bone (lymphoid neoplasia) marrow aspirate, adrenal function tests) 3. Administer chemotherapy agents at the maxi- B. Diagnostic imaging mal tolerated dose 1. Radiographs (thorax, abdomen, skeleton) 4. Continue chemotherapy after apparent remis- should be taken to determine the presence of sion because a microscopic tumor remains after metastases the tumor can no longer be physically detected 2. Ultrasound is most useful to visualize the 5. Tumors can become drug resistant; the larger abdomen the tumor, the more likely that it will become C. Cytology resistant 1. Can provide rapid and inexpensive diagnostic 6. Patients should be reevaluated at regular information intervals post therapy 2. Do not overinterpret cytology preparations D. Nutritional management 3. Definitive diagnosis most often requires 1. Anorexia is common (cancer cachexia) and histopathology may be related to the side effects of therapy or D. Biopsy to tumor-produced anorexigenic substances 1. Larger samples provide a more accurate diag- 2. Provide enteral or parenteral feeding if pa- nosis tients do not eat for more than 5 days or have 2. Fix tissue samples in 10% buffered formalin an acute loss of 10% or more of body weight 3. Histologic samples should contain the neoplas- 3. Malnourished patients show hypoalbuminemia, tic tissue with a margin of normal tissue lymphopenia, and anemia III. Principles of therapy 4. Malnutrition adversely impacts the immune A. Surgery system, delays wound healing and cell repair, 1. Most useful for localized tumors and increases morbidity and mortality 2. Resect all neoplastic tissue, if possible with E. Pain management wide margins 1. Acute vs. chronic; treatment vs. tumor-related 3. Prevent surgical spread of cancer cells 2. Contributes to anorexia, weight loss, reduced a. Minimize the manipulation of the tumor mobility, depression b. Protect healthy tissues from tumor cell con- 3. Prevention or early treatment of pain is more tamination with the use of barrier drapes effective than treating severe or chronic pain c. Change gloves, drapes, and instruments 4. Provide pain relief with minimal sedation and during surgery if necessary other side effects 297 298 SECTION II SMALL ANIMAL 2. Alimentary lymphoma is associated with LYMPHOID NEOPLASIA gastrointestinal (GI) signs such as vomiting, I. Lymphoma diarrhea, weight loss, and lethargy A. Cause 3. Mediastinal lymphoma usually causes respira- 1. Retrovirus can cause lymphoma in the cat, tory signs. Most mediastinal lymphomas are chicken, and human associated with hypercalcemia 2. In the cat, both FeLV and feline immunodefi- 4. Cutaneous lymphoma varies in appearance. ciency virus (FIV) can cause lymphoma Many are pruritic 3. In the dog, a viral etiology has not been 5. Extranodal lymphoma includes lymphoma in established the eye, central nervous system (CNS), bones, 4. Genetics may play a role; exposure to environ- heart, kidneys, urinary bladder, and nasal mental carcinogens may also play a role in cavity development 6. B-cell vs. T-cell lymphoma B. Classification and clinical signs (Tables 21-1 and a. In the dog, most are B-cell lymphomas. 21-2) T-cell lymphoma is associated with hyper- 1. Multicentric lymphoma is the most common calcemia, and cranial mediastinal tumors form in the dog. Enlarged lymph nodes are b. Most FeLV associated lymphomas in cats typically palpated. Other clinical signs include are T-cell lymphomas weight loss, decreased appetite, polyuria (PU)/ 7. Most animals are middle-aged or older polydipsia (PD), and lethargy. Enlargement of C. Diagnosis the liver and spleen are commonly seen 1. Physical examination a. Palpate all lymph nodes b. Evaluate organ involvement, especially liver or kidney involvement c. Bone marrow involvement can cause hema- Table 21-1 World Health Organization Clinical Staging tologic abnormalities for Domestic Animals with Lymphoma d. Ophthalmic problems such as uveitis, hem- orrhage, and ocular infiltration occur in Stage Criteria about 33% of dogs with lymphoma 2. Laboratory evaluation I Single lymph node a. Immature lymphocytes are usually seen in II Multiple lymph nodes in a regional area the circulation III Generalized lymphadenopathy b. Normocytic, normochromic, nonregenera- IV Liver or spleen involvement (with or tive anemia is common without stage III) c. Bone marrow aspirate may show neoplastic V Bone marrow or blood involvement or lymphocytes any nonlymphoid organ (with or d. Hypercalcemia is seen in about 20% of without stages I to IV) those with lymphoma Substage a Without clinical signs of disease e. Increased blood urea nitrogen and creatinine Substage b With clinical signs of disease may be seen with kidney involvement f. If there is liver involvement, liver enzymes may be increased World Health Organization (WHO). TNM Classification of Tumors in g. Most cats with mediastinal or multicentric Domestic Animals. Geneva, 1980, WHO. lymphoma are FeLV positive Table 21-2 Characteristics of Feline Lymphoma by Anatomic Site Anatomic Site Relative Frequency Age T-Cell Association FeLV Positive Alimentary 50%-70% ⬃10-14 yr High Low (5%) Multicentric 10%-25% Depends on feline leukemia Depends on FeLV Approximately virus (FeLV) status* status* one third Mediastinal/thymic 10%-20% Young High High (80%) Nasal ⬃10% Aged Low Low Renal 5%-10% Middle-aged Low to moderate Low to moderate Other 5%-25% Mixed Mixed Mixed *FeLV-positive cats tend to be younger, and the cancer is more commonly of T-cell derivation. From Ettinger SJ, Feldman EC, editors. Textbook of Veterinary Internal Medicine, 6th ed. St Louis, 2005, Saunders.  CHAPTER 21 Oncology 299 3. Diagnostic imaging 6. If cytopenia is present, prednisone, a. Radiography/ultrasound can be helpful to L-asparaginase, and vincristine are used, as evaluate organ involvement these agents tend to spare the bone marrow. b. Thoracic radiographs should be taken in However, if cytopenia is the result of bone any case of hypercalcemia of unknown marrow infiltration, aggressive chemother- origin apy is required c. Enlarged sternal and sublumbar lymph 7. Reinduction and Rescue therapy nodes occur in about half of lymphomas a. If a patient that has previously been in 4. Histopathology of lymph nodes is recom- remission has a recurrence of lymphoma, mended. With cytology, neoplasia can be the same protocol that was used initially difficult to distinguish from benign lymphade- should be reintroduced. After reinduction, nopathy the length of remission is typically half 5. Other tests that initially used a. May need to do an exploratory laparotomy b. Rescue therapy is instituted when remission b. Cerebrospinal fluid cytological evaluation cannot be obtained with the regular proto- may help in the diagnosis of CNS lymphoma col. Drugs used for rescue include mitoxan- in the dog trone, L-asparaginase, lomustine, and 6. Differential diagnosis actinomycin-D. Remissions achieved with a a. Lymphadenopathy differentials include rescue protocol are generally short infectious diseases, immune-mediated 8. Small cell lymphomas tend to be more resis- diseases, and other metastatic neoplasia tant to therapy. Chlorambucil and prednisone b. Differentials for alimentary lymphoma in- therapy appear helpful clude lymphocytic enteritis, other intestinal 9. Surgery combined with radiation therapy and neoplasias, granulomatous disease, and chemotherapy may be beneficial in CNS lym- hypereosinophilic syndrome phoma c. Differentials for mediastinal lymphoma in- 10. Cutaneous lymphoma is resistant to chemo- clude thyroid tumors, heart base tumors, therapy and may be able to be treated with thymoma, and pulmonary granulomatosis surgery and radiotherapy. Lomustine, retinoic d. Differentials for cutaneous lymphoma acid, or L-asparaginase may be beneficial include pyoderma, immune-mediated E. Prognosis disorders, parasitic skin disorders, and 1. Dogs other cutaneous neoplasia a. Stage V, or substage b, are associated with D. Treatment shorter remission and survival times 1. Require chemotherapy. Without treatment, b. T-cell lymphoma has a shorter remission most live only 4 to 6 weeks after diagnosis and survival time 2. With chemotherapy, up to 90% of dogs and c. Female dogs may have a longer survival 70% of cats enter remission and survive up to time a median of one year. Cures are uncommon, d. Hypercalcemia is associated with T-cell but about 25% can live 2 or more years. If cats lymphoma and a worse prognosis can achieve remission, they can survive for e. GI lymphoma, disseminated cutaneous, or long periods leukemic forms have a poorer prognosis 3. Cats have fewer adverse effects unless they are 2. Cats treated with doxorubicin. Do not give doxoru- a. The higher the clinical stage, the poorer the bicin to cats with renal disease prognosis 4. Combination protocols tend to be more b. FeLV positive cats have a poorer prognosis effective, with longer remissions and survival c. The presence of leukemia, anemia, neutro- time; they are also more costly and more penia, and sepsis worsen the prognosis time-consuming d. Cats that achieve remission early have a 5. Protocols: A number of protocols are available. better prognosis The most common protocols are discussed be- II. Lymphoid leukemia low: A. Acute lymphoblastic leukemia (ALL) a. The CHOP combination protocol (C  1. Clinical signs cyclophosphamide, H  hydroxydaunorubi- a. Signs include fever, abdominal pain, an- cin [doxorubicin], O  Oncovin [Vincristine], orexia, splenomegaly, and pale mucous P  prednisone) (University of Wisconsin- membranes Madison Short Protocol). Patients are off all b. Dogs are usually late middle-aged; affected medication after 19 weeks. L-asparaginase is cats are younger no longer a part of this protocol; c. Anemia occurs in most patients; 25% are L-asparaginase is reserved for “rescue” thrombocytopenic b. Doxorubicin used alone achieves remission d. Almost all cats with ALL also have FeLV in about 70% of dogs 2. Diagnosis c. Prednisone used alone is inexpensive, but a. Documentation of abnormal lymphocytes in the survival time is only about 2 months bone marrow or blood 300 SECTION II SMALL ANIMAL b. Most have leukocytosis; about 10% have b. Other differentials include carcinomas, aleukemic leukemia (bone marrow involve- connective tissue disorders, liver disease, ment with no peripheral blood involve- hypersensitivity, and infections ment). Special stains may be needed 4. Treatment c. Differentiate from lymphoma. ALL has a a. In the dog, the short-term prognosis is more acute progression and less likelihood good; in the cat the prognosis is poor of lymphadenopathy; patients have a poor b. Chemotherapy includes melphalan and response to therapy and shorter survival prednisone. Remission occurs in about 90% times of cases 3. Treatment c. Once remission is lost, a combination of a. CHOP-based protocol doxorubicin, vincristine, and dexametha- b. Poor prognosis sone may be helpful B. Chronic lymphocytic leukemia (CLL) B. Plasmacytoma 1. Clinical signs 1. Solitary plasmacytoma a. Most dogs have lymphadenopathy and a. Rare; tends to progress to multiple splenomegaly, pale mucous membranes, myeloma and fever b. Can treat with surgery or radiation therapy; b. Clinical signs are usually nonspecific (leth- use melphalan and prednisone if there is argy, PU, PD, intermittent lameness, epi- systemic involvement sodes of collapse, bleeding gums, epistaxis) 2. Extramedullary plasmacytoma 2. Clinical pathology a. Oral or cutaneous extramedullary plasma- a. Most have normocytic, normochromic, cytomas are usually benign nonregenerative anemia, thrombocytopenia b. GI extramedullary plasmacytoma behaves b. About one third have hyperproteinemia like a malignancy. If it is localized, excision with monoclonal gammopathies can be attempted c. Cats are FeLV negative 3. Treatment SARCOMAS AND MAST CELL TUMORS a. Treatment is recommended only in symp- tomatic patients I. Soft tissue sarcomas b. In dogs, prednisone and chlorambucil are A. Cause most commonly used 1. Unknown c. The prognosis for CLL is better than that 2. Genetics may play a role since some breeds for ALL (boxers, German shepherd dogs, Great Danes, III. Plasma cell neoplasia Saint Bernards, golden retrievers, basset A. Multiple myeloma hounds, flat-coated retrievers) are at 1. Clinical signs increased risk a. Occurs in older dogs; no sex predilection 3. Viral agents may play a role in cats, rodents, b. Nonspecific clinical signs (anorexia, listless, poultry, and nonhuman primates PU, PD) 4. Chemical carcinogens, ionizing radiation, c. Most have lameness secondary to bone chronic tissue inflammation, trauma, and pain vaccinations are also potential causes d. Epistaxis and gingival bleeding due to hy- B. Biologic behavior perviscosity syndrome occurs in about 50% 1. Usually invasive and infiltrative with poorly of cases defined margins 2. Diagnosis 2. Metastasis depends on the grade of the tumor a. About 75% of dogs have a monoclonal C. Types gammopathy, usually immunoglobulin G 1. Liposarcoma or immunoglobulin A a. Originate from adipocytes b. Bence Jones proteins may be present in the b. Rare; invasive and aggressive urine (cannot be detected by urine dipstick) c. Metastasis is uncommon c. May have a nonregenerative, normocytic, 2. Hemangiopericytoma normochromic anemia. Thrombocytopenia a. Originates from the pericytes, which occurs in about 30%; 10% have circulating surround arterioles abnormal plasmacytes b. German shepherd dogs have an increased d. About 20% have hypercalcemia secondary risk to bone resorption c. Infiltrative; recurrence is common e. For diagnosis, three abnormalities should d. Rarely metastasize be present: Bone marrow plasmacytosis, e. Usually on extremities osteolytic bone lesions, and serum or urine 3. Fibrosarcoma myeloma proteins a. Common 3. Differential diagnosis b. Invasive but slow growing a. Ehrlichiosis can also cause a monoclonal c. Usually do not metastasize (except for gammopathy injection-site sarcomas)  CHAPTER 21 Oncology 301 4. Hemangiosarcoma F. Treatment a. Originates from endothelium of blood 1. Surgical excision (with wide margins) is the vessels treatment of choice b. Rapid growing; invasive 2. Radiation therapy is used when the tumor c. German shepherd dogs at increased risk; cannot be completely excised rare in cats 3. Hyperthermia treatment is used in combina- d. Usually in spleen, heart, and skin; metasta- tion with radiation or chemotherapy sis is common 4. Chemotherapy is used best after incomplete e. May cause collapse if the tumor ruptures excision. Agents used include vincristine, with hemorrhage doxorubicin, cyclophosphamide, 5. Neurofibrosarcoma mitoxantrone, dacarbazine, carboplatin, a. Originates from nerve sheaths and lomustine b. Slow growing, but invasive; metastasis is II. Mast cell tumors (MCTs) rare A. Cause c. Commonly in the brachial or lumbosacral 1. Unknown plexus; may see progressive lameness 2. Breeds at higher risk: boxers, Boston terriers, 6. Myxosarcoma English bulldogs, English bull terriers, a. Rare Chinese shar-peis, Labrador retrievers, b. Infiltrative, but metastasis is uncommon golden retrievers. In boxers, MCTs are usually 7. Rhabdomyosarcoma well-differentiated. Siamese cats have a high a. Originate in striated muscle incidence of histiocytic MCT b. Infiltrative; metastasis can occur 3. Chronic inflammation and viruses may play a c. Usually in heart, urinary bladder, and role in development appendicular muscle B. Biologic behavior 8. Leiomyosarcoma 1. About half of dogs have well-differentiated, a. Originates in smooth muscle grade 1 tumors, which are cured with excision. b. Rare; infiltrative but slow growing Undifferentiated tumors are in up to 40% of c. Common sites are spleen, liver, GI tract, patients and are aggressive and urinary tract; metastasis is possible 2. Preputial, inguinal, perineal, oral, and aural d. May cause hypoglycemia tumors are more aggressive 9. Synovial cell sarcoma 3. Slow-growing MCTs have a better prognosis a. Originates in the periarticular mesenchy- 4. Metastasis is to lymph nodes, spleen, and liver. mal tissue The bone marrow may also be involved. Metas- b. Aggressive; metastasis occurs tasis to the lungs is uncommon c. Large-breed dogs at increased risk 5. In cats, most are well-differentiated. Histiocytic 10. Lymphangiosarcoma MCT occurs in young cats and may spontane- a. Originates in the lymphatic endothelial ously regress. Visceral MCTs are aggressive vessels and metastasize b. Rare; invasive but metastasis is rare C. Clinical signs c. May see edema or draining tracts on the skin 1. Dog: Solitary mass in skin of trunk, perineal 11. Malignant fibrous histiocytoma area, extremities, or head and neck. Cat: Soli- a. Contains a mixture of fibroblast and histio- tary mass on head and neck; about 20% of cats cytic cells have multiple masses b. Usually subcutaneous 2. Usually well-defined and raised; can be hairless c. Invasive, but metastasis is uncommon. and ulcerated. If subcutaneous, they can May cause bone lysis resemble lipomas 12. Injection-site sarcomas (feline) 3. Visceral MCTs can occur in the spleen, intestine, a. Usually fibrosarcomas but may be a rhab- liver, and lymphatics. Animals may present with domyosarcoma, leiomyosarcoma, chondro- anorexia, vomiting, and diarrhea sarcoma, osteosarcoma (OSA), malignant D. Diagnosis fibrous histiocytoma, or undifferentiated 1. A CBC should be examined for evidence of sarcoma circulating mast cells (more common in the b. The number of giant cells present corre- dog). There may be a microcytic, hypochromic lates with the grade anemia if there is GI hemorrhage c. Invasive and aggressive; metastasis occurs 2. A bone marrow aspirate should be performed D. Clinical signs if there is suspected bone marrow involvement 1. Depends on location, size, invasiveness, and 3. Abdominal radiographs may reveal hepatomeg- presence of metastases aly, splenomegaly, or abdominal lymph node 2. More common in older animals enlargement E. Diagnosis 4. A fine-needle aspirate of a mass is usually diag- 1. Malignant tumors are fast growing and invasive nostic. Histopathology is necessary to ensure with poorly defined borders that excision is complete and for grading the 2. Look for metastases tumor 302 SECTION II SMALL ANIMAL E. Treatment C. Administration of progestins increases the risk 1. Surgical excision (with wide margins) is the D. Dogs that have had a benign mammary gland treatment of choice tumor are at higher risk for developing a 2. Mast cells release histamine; give an antihista- mammary tumor of a different type mine before surgery II. Clinical signs 3. If the tumor cannot be completely excised, A. Mass or swelling on the ventral thorax of abdomen a combination of radiation therapy or chemo- B. Metastatic lesions may cause dyspnea, bone pain, therapy can be attempted. Also irradiate or lameness regional lymph nodes C. May see anorexia and weight loss, especially in 4. Chemotherapy is recommended in systemic cats with inflammatory mammary carcinoma (IMC) mastocytosis. Vinblastine, cyclophosphamide, III. Diagnosis or lomustine in combination are used A. Signalment 5. Give histamine type 2 (H2)-antagonists (famoti- 1. Risk increases after 6 years of age dine, ranitidine, cimetidine) to reduce gastric 2. Sporting breeds, poodles, Boston terriers, and acid secretion. Give H1-antagonists (diphen- dachshunds are at increased risk hydramine) to reduce inflammation associated 3. In cats, most occur in intact females; Siamese with histamine have an increased risk 6. In cats, splenectomy may increase the survival, B. History: A mass is usually noted by the owner, or even if other organs are involved. Chemother- it may be an incidental finding apy has not been well evaluated in cats C. Physical examination III. Skeletal neoplasias 1. Most often occur in the caudal mammary glands A. Osteosarcoma (OSA) 2. Inflammatory tumors have diffuse swelling, 1. About 85% of primary bone tumors in dogs are which may look like mastitis OSAs 3. Lymph nodes may be enlarged (superficial 2. OSA is usually aggressive and found in meta- cervical, axillary, popliteal, inguinal) physic of long bones. The radius is the most D. Diagnostic imaging common site. Most have pulmonary metastatic 1. Mammary tumors commonly metastasize to disease the lungs 3. Large and giant breeds may be predisposed 2. Evaluate the iliac lymph nodes with radio- 4. In cats, OSA is less aggressive, and the graphs or ultrasound hindlimb is more commonly affected E. Cytology 5. Treatment is amputation with chemotherapy. 1. Aspirates of the mammary tumor are not rec- Cisplatin, carboplatin, and doxorubicin are ommended as many have inflammation, which frequently used for chemotherapy makes tumor grading difficult 6. The prognosis is poor if there are pulmonary 2. Cytology can help differentiate a tumor from metastases, an elevated alkaline phosphatase, mastitis or OSA is found in a young patient. Long-term 3. Lymph nodes can be aspirated prognosis is poor F. Histology B. Chondrosarcoma 1. About 50% are benign 1. About 5% to 10% of primary bone tumors are 2. Dogs can have multiple tumors of different types chondrosarcomas 3. Remove regional lymph nodes for histopathol- 2. Medium-sized to large-breed dogs are more ogy. If lymph node involvement is noted, prog- commonly affected nosis is poorer 3. Surgical resection increases survival, but IV. Treatment long-term prognosis is still poor A. Surgical C. Fibrosarcomas and hemangiosarcomas are the 1. Surgery is not recommended for cases of IMC next most common bone tumors in dogs because it is difficult to remove all the affected D. Metastatic bone tumors tissue, and disseminated intravascular coagula- 1. Carcinomas are more likely to metastasize tion is often induced by surgery to bone 2. Surgery is the treatment of choice for mam- 2. Metastasis to bone usually causes tumors in mary gland tumors (except for IMC) the diaphysis; primary tumors are usually in 3. Wide excision is important the metaphysic 4. Lumpectomy can be performed if the tumor is 3. Prostatic carcinomas, transitional cell carcino- very small and noninvasive mas, and mammary cell carcinomas tend to 5. Simple mastectomy (removal of one gland) is metastasize to bone relatively simple 6. Multiple glands may be removed if the tumor is extensive MAMMARY GLAND NEOPLASIA 7. When multiple, nonadjacent glands are involved, I. Cause perform a complete unilateral mastectomy A. Unknown; genetics or a virus may play a role B. Medical therapy has been used in conjunction B. Dogs spayed before the first estrus have a greatly with surgery to treat metastases reduced risk 1. Efficacy has not been established  CHAPTER 21 Oncology 303 2. Cyclophosphamide and 5-fluorouracil have dogs. Some papillomas in older dogs can trans- been used in dogs; cyclophosphamide and form into squamous cell carcinoma doxorubicin have been used in cats 4. In young dogs, papillomas regress spontane- V. Prognosis ously. Surgically remove if they do not regress A. In cats, tumor size in important. Cats with tumors B. Sebaceous gland tumors (epithelial) greater than 3cm in diameter have a poorer 1. Originate from the epithelium of the sebaceous prognosis glands B. In dogs, histologic grade and stage are most 2. Common in older female spaniels and poodles; important rare in cats 1. If the tumor is invasive or metastatic, the 3. Adenoma is usually a wart-like growth that is mortality rate is 80% smooth, pink, and well-circumscribed. They 2. Most deaths occur within 1 year of surgery are often ulcerated and bleeding. Sebaceous 3. About 26% with benign tumors develop new gland adenocarcinomas are invasive and very masses within 2 years of the initial surgery rare. Carcinomas metastasize to lymph nodes 4. Poorly differentiated tumors have a poorer and lungs prognosis 4. Surgical excision is the treatment of choice. 5. Ductular carcinomas metastasize more Carcinomas may require radiation therapy frequently compared with adenocarcinomas and/or chemotherapy C. Perianal tumors (epithelial) 1. Originate from the perianal glands (sebaceous SKIN AND SUBCUTANEOUS glands surrounding the anus; also in skin of the TISSUE TUMORS tail, prepuce, thigh, and dorsum of back). They I. Introduction are dependent on the presence of testosterone A. More common in older dogs and cats 2. Solitary or multiple; usually benign; common B. Most common site of neoplasia in the dog; the in older intact male dogs. Carcinomas are ul- second most common site in the cat cerative and invasive. Carcinomas metastasize C. Most skin tumors in dogs are benign; most in the to lymphatics, iliac lymph nodes, and lungs cat are malignant 3. Adenomas regress with castration. Adenocarci- D. Dog breeds at increased risk include the basset nomas should be radically excised; also treat hound, boxer, bullmastiff, Scottish terrier, and with radiation or chemotherapy (carboplatin, Weimaraner; no breed predilection in the cat mitoxantrone, and doxorubicin) E. Most common tumors in young dogs are histiocy- D. Basal cell tumors (epithelial) toma, transmissible venereal tumors, and viral 1. Originate from basal cells of the epidermis and papillomas adnexa F. Most common tumors in dogs include lipomas, 2. Usually solitary, firm, well demarcated, and MCTs, histiocytomas, and sebaceous gland ade- pigmented. Found on the head, neck, and nomas; most common tumors in cats shoulders in the dog; anywhere in the cat (the include basal cell tumors, squamous cell carcino- most common skin tumor in cats) mas, fibrosarcomas, and MCTs 3. On cytology, cells are arranged in cords II. Diagnosis 4. Common in older dogs and cats; cocker A. Cytology spaniels and poodles are at increased risk 1. Malignant vs. benign 5. Usually benign; basal cell carcinomas are 2. Epithelial, mesenchymal, or round cell neoplasm aggressive 3. Inflammatory vs. noninflammatory 6. Surgical excision is the treatment. Treat 4. Evaluate enlarged regional lymph nodes carcinomas with radiation and chemotherapy B. Biopsy E. Ceruminous gland tumors (epithelial) 1. Either incisional or excisional 1. Originate from the ceruminous epithelium in 2. Submit all tumors removed for histopathology the ear canal C. Radiographs 2. Usually brown tumors with cerumen production; 1. Thoracic radiographs if malignancy is suspected small and located near the tympanic membrane 2. Abdominal radiographs/ultrasound to evaluate 3. More common in cats involvement of liver and spleen (especially if 4. Total ear canal ablation may be necessary MCT or hemangiosarcoma) to excise. Irradiation is recommended with III. Types adenocarcinomas and incomplete resection. A. Papilloma (epithelial) Chemotherapy includes cisplatin, carboplatin, 1. Originates from the squamous epithelium. In mitoxantrone, and doxorubicin puppies, there is a viral cause F. Squamous cell carcinoma (epithelial) 2. Cauliflower or wart-like mass; may bleed if 1. Originates from the squamous epithelium. Oc- traumatized. Usually single nodule but can be curs secondary to ultraviolet light exposure in multiple if cause is viral hypopigmented areas 3. Common in dogs; rare in cats. Viral-induced 2. Occur more frequently in white cats; on ear papillomas are usually on the head, eyelids, tips and nose. In dogs they occur primarily on feet, or mouth and are contagious to other the ventral abdomen, trunk, scrotum, and lips 304 SECTION II SMALL ANIMAL 3. Locally invasive; late to metastasize (to lymph L. Hemangiosarcoma (mesenchymal) nodes and lungs) 1. Originates from the vascular endothelium 4. Surgical excision is the treatment if possible. 2. Solitary masses, usually on the limbs, flanks, Can also use radiation therapy or chemother- or neck apy with cisplatin, carboplatin, bleomycin, 3. More common in German shepherd dogs and mitoxantrone, or doxorubicin golden retrievers G. Anal sac/apocrine gland adenocarcinoma 4. If the tumor is subcutaneous or involves (epithelial) muscle, prognosis is poorer 1. Originate from the apocrine glands that secrete 5. Treatment is by surgical excision. If it involves into the anal sac subcutaneous tissue, then also treat with 2. Can vary in size from very small to large doxorubicin masses protruding from the rectum M. Histiocytoma (round cell) 3. Most common in the older female dog. Metas- 1. From monocyte or macrophage cells in the skin tases to regional lymph nodes are common 2. Usually on the head; round, alopecic, and pink. 4. Often associated with hypercalcemia, and the Look like a ‘button” secretion of parathyroid hormone–related 3. Typically in young dogs (i.e., 1 to 3 years of protein age); do not occur in cats 5. Treatment is surgical excision; also chemother- 4. Most spontaneously regress within 4 to 8 weeks apy with carboplatin or mitoxantrone 5. Surgically remove if they do not regress H. Keratoacanthoma (epithelial) N. Melanoma (round cell) 1. Originates from the epithelium between hair 1. Originates from melanocytes or melanoblasts follicles 2. Usually brown to black pigmented nodules and 2. Located on the neck, dorsal thorax, legs, and occurs more commonly on the face, trunk, feet, ventral abdomen. Can express a toothpaste- mucocutaneous regions, and nail beds like material 3. More common in dogs than in cats 3. Benign; solitary in most breeds, though multi- 4. Tumors in the skin are usually benign; tumors ple in Norwegian elkhounds and keeshonden of mucocutaneous regions are usually malignant 4. Treatment is surgical excision. Retinoid ther- 5. Surgery is the treatment of choice. Recurrence apy for the multicentric form and metastases are common I. Dermoid and epidermal inclusion cyst (epithelial) O. Transmissible venereal tumor (round cell) 1. Inclusion cysts are typically secondary to an 1. Transmitted via mating or close contact occluded hair follicle. Dermoid cysts are a 2. Occur on the external genitalia and face developmental defect 3. May be multiple; friable, ulcerated, cauliflower- 2. Benign like masses 3. Treatment is surgical excision 4. Treatment is surgery, vincristine chemother- J. Lipomas/liposarcomas (mesenchymal) apy, or radiation therapy 1. Originate from adipocytes 2. Lipomas are usually soft and well circum- Supplemental Reading scribed. Liposarcomas are rare, usually soli- tary, infiltrative, firm, poorly circumscribed, Davis KM, Stone EA. Mammary gland neoplasia. In Birchard and metastasize to the lungs and liver SJ, Sherding RG, eds. Saunders Manual of Small Animal 3. Lipomas are more common in older spayed Practice, 3rd ed. St Louis, 2006, Saunders , pp. 311-315. female dogs; the most common mesenchymal Gilson SD, Page RL, Gamblin RM. Principles of oncology. In tumor in the dog. Rare in the cat Birchard SJ, Sherding RG, eds. Saunders Manual of Small 4. Lipomas may not need to be removed. Liposar- Animal Practice, 3rd ed. St Louis, 2006, Saunders, pp. comas should be surgically removed and 283-291. treated with radiation therapy if there are Graham JC. Soft tissue sarcomas and mast cell tumors. In incomplete margins on histopathology Birchard SJ, Sherding RG, eds. Saunders Manual of K. Fibrosarcoma (mesenchymal) Small Animal Practice, 3rd ed. St Louis, 2006, Saunders, 1. Originates in the fibrous connective tissue pp. 301-310. from fibrocytes or fibroblasts Palmisano M, Miovancev M. Neoplasia of thoracic and 2. Occurs in association with feline sarcoma virus pelvic limbs. In Birchard SJ, Sherding RG, eds. Saunders or FeLV in cats; either sporadic, or at sites of Manual of Small Animal Practice, 3rd ed. St Louis, 2006, vaccination. Prevalence of vaccine-associated Saunders, pp. 1176-1185. fibrosarcomas is 1-3:10,000 cats Peterson JL. Tumors of the skin and subcutaneous tissues. 3. Usually on the head, trunk, or limbs In Birchard SJ, Sherding RG, eds. Saunders Manual of 4. In older dogs and cats, usually solitary; in Small Animal Practice, 3rd ed. St Louis, 2006, Saunders, younger cats where associated with feline pp. 316-326. sarcoma virus, they are multiple Vail DM. Lymphoid neoplasia. In Birchard SJ, Sherding RG, 5. Locally invasive but late to metastasize eds. Saunders Manual of Small Animal Practice, 3rd ed. St 6. Treatment: Wide and deep surgical excision. Louis, 2006, Saunders, pp. 292-300. Chemotherapy with doxorubicin or Withrow SJ, Vail DM. Small Animal Clinical Oncology, 4th ed. mitoxantrone St Louis, 2007, Saunders.