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Mammary Gland Neoplasia, Cat 621

Mammary Gland Neoplasia, Cat Client Education
Sheet
VetBooks.ir Diseases and Disorders

enzyme leading to conversion of arachi-
BASIC INFORMATION
• Discharge from nipple is possible.
donic acid to prostaglandins; upregulated • Ulceration is frequently present.
Definition expression is associated with a poorer • Regional lymph nodes (inguinal and
Mammary gland tumors are common tumors prognosis. axillary) may be enlarged or normal on
arising from mammary tissue. Mammary palpation.
tumors can be benign or malignant. RISK FACTORS • Lymph node enlargement can indicate
• Ovariohysterectomy (OHE) reduces the risk metastasis or reactive change secondary to
Synonyms of cats developing mammary tumors. inflammation.
• Mammary or breast cancer/tumor ○ OHE < 6 months: 91% risk reduction • Inflammatory carcinomas occur rarely in cats
• Specific mammary neoplasms: adenoma, compared with that of intact cats after mastectomy for mammary carcinoma
fibroadenoma, carcinoma in situ, tubulopap- ○ OHE 7-12 months: 86% risk reduction and rarely as a primary entity. Cats with this
illary carcinoma, solid carcinoma, cribriform compared with that of intact cats form of mammary neoplasia present with
carcinoma, inflammatory carcinoma ○ OHE 13-24 months: 11% risk reduction local erythema, edema, pain, and involve-
compared with that of intact cats ment of the extremities.
Epidemiology ○ OHE > 2 years: no benefit
SPECIES, AGE, SEX • Treatment with progesterone and estrogen/ Etiology and Pathophysiology
• Mammary gland tumors represent up to 20% progesterone combinations: threefold increased • The vast majority (>85%) of feline mammary
of all tumors in female cats. risk of development of benign and malignant tumors are malignant, with > 80%
• Third most common tumor in cats mammary tumors in cats of feline mammary tumors classified as
• Mean age is 10-12 years. Clinical Presentation adenocarcinoma.
• Most common: malignant epithelial ○ Metastasis is common (>80%). Common
carcinoma/adenocarcinoma DISEASE FORMS/SUBTYPES sites of metastasis include the lungs,
• Mixed mammary tumors (combination of Clinical staging: pleura, and lymph nodes.
epithelial and myoepithelial components) • Tumor: T1 < 2 cm; T2 2-3 cm; T3 > 3 cm • Inflammatory carcinomas occur rarely in
and sarcomas are rare. • Regional lymph node: N0, no metastasis; cats after mastectomy for mammary carci-
• Siamese cats may develop mammary tumors N1, metastasis detected noma.
at an earlier age than other breeds. • Distant metastasis: M0, no metastasis; M1, ○ These are aggressive anaplastic carcinomas
• Mammary tumors are rare in male metastasis detected with considerable inflammatory cell infil-
cats (1%-2% of feline mammary carcino- trate, intradermal and dermal lymphatic
mas). invasion that leads to edema, pain, and
rapid metastasis.
GENETICS, BREED PREDISPOSITION Stage Grouping T N M • Benign tumors, including adenomas,
• Siamese cats have a twofold risk of devel- I T1 N0 M0 fibroadenomas, and duct papillomas, occur
oping mammary gland tumors and have a II T2 N0 M0 uncommonly in cats (<15%).
higher incidence of malignant tumors with III T1, T2 N1 M0
lymphatic invasion. DIAGNOSIS
• Persian cats may have a higher incidence of T3 N0, N1 M0
benign mammary tumors. IV T1-3 N0, N1 M1 Diagnostic Overview
• A genetic factor in the development of • The diagnosis is suspected based on the
mammary tumors has not been identified. detection of a mass in the mammary chain.
The following oncogenes/molecular markers Histologic evaluation is required for definitive
have shown abnormal expression in selected HISTORY, CHIEF COMPLAINT diagnosis and is usually obtained from an
feline mammary gland tumors: • The owner may notice a swelling, lump, excisional biopsy.
○ TP53: gene encodes tumor protein 53, or ulcerated tissue in a cat’s mammary • Incisional biopsy can be considered in
which regulates the cell cycle and func- chain. cases where a benign tumor is suspected,
tions as a tumor suppressor; mutation • In cases of metastasis or inflammatory carci- but radical mastectomy with removal of all
detected more frequently in carcinomas noma, cats may be presented for general signs four glands and ipsilateral lymph node(s) is
than benign tumors of illness or specific complaints attributable advised for firm, fixed, or ulcerated masses
○ ERBB2 (HER2/NEU): gene involved in to a certain site of metastasis (e.g., dyspnea or when malignancy is confirmed. A diag-
signal transduction and overexpression due to pulmonary metastases or pleural nostic and treatment approach is presented
noted in more aggressive feline mammary effusion). on p. 1433.
tumors • Duration of clinical signs varies, ranging
○ VEGF (vascular endothelial growth factor): from a few days to several months. Differential Diagnosis
gene encodes an angiogenic factor that • Fibroepithelial hyperplasia: involves one
contributes to growth, invasion, and PHYSICAL EXAM FINDINGS or multiple glands, most often in young
metastasis of tumor; overexpression seen • >50% of cats have more than one mammary intact females and spayed females given
in poorly differentiated tumors tumor, and both mammary chains may be progesterone compounds.
○ CCNA1/CCNA2 (cyclin A1/A2): gene affected simultaneously. • Mastitis
regulates the cell cycle and may be • Tumors may be firm on palpation and • Other cutaneous and subcutaneous tumors
associated with tumorigenesis in feline occasionally fixed to underlying structures. • Inguinal/axillary lymphadenopathy (reactive,
mammary carcinoma • Discrete to infiltrative, soft to firm swelling neoplastic)
○ PTGS2 (prostaglandin-endoperoxide in the mammary gland or overlying skin is • Inguinal hernia
synthase 2/COX2): gene encodes an most common. • Enlarged inguinal fat pad

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