Page 155 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

134 PART II Diagnostic Procedures for the Cancer Patient

cytologically, the greater the number of malignant criteria pres- and centrally located, with reticular chromatin and a single nucleo-
ent within any of the cell types, the more likely the tumor is lus. A population of reserve cells with high N:C ratios may be found
at the periphery of the clusters. Occasionally, a perianal gland tumor
malignant; however, even tumors with mild pleomorphism may
VetBooks.ir be malignant. Features that define inflammatory mammary car- may consist exclusively of reserve cells and is termed a perianal gland
epithelioma. Although the majority of these tumors are benign, pleo-
cinomas histologically, such as the presence of tumor emboli in
lymphatic vessels, cannot be appreciated cytologically, and this morphic features are not prominent even in the malignant tumors.
diagnosis is suspected when epithelial cells have cytologic criteria
of malignancy and when typical clinical signs such as erythema, Tumors of the Apocrine Gland of the Anal Sac
swelling, and warmth are identified. Mammary hyperplasia can- Tumors of the apocrine gland of the anal sac and perianal gland
not be differentiated cytologically from neoplastic proliferation of tumors are the most common tumors in the perianal region
tubular cells in the absence of pleomorphic features, and knowing and with experience can be reliably differentiated cytologically.
the stage of the reproductive cycle in intact females can be helpful. Although not of neuroendocrine origin, apocrine adenocarcino-
mas resemble other tumors with a neuroendocrine appearance (see
Perianal Gland Tumors later). Even though pleomorphism is minimal, these tumors are
Perianal gland tumors, also called circumanal or hepatoid tumors, malignant and frequently metastasize to the medial iliac LNs and
have a characteristic appearance and with experience can be differ- eventually beyond. Pleomorphism is usually limited to mild to
entiated from tumors of the apocrine gland of the anal sac. Cells moderate anisokaryosis with occasional macronuclei.
are arranged in cohesive clusters and resemble hepatocytes, having
uniformly low N:C ratios and abundant amphophilic granular cyto- Tumors of the Prostate Gland
plasm with distinct margins (Fig. 7.13). Nuclei are uniformly round Tumors of the prostate gland have features similar to other glan-
dular tumors. Sometimes the cells contain circular granular eosin-
ophilic inclusions (see Transitional Cell Carcinomas [TCCs]).
Primary prostatic carcinomas cannot be easily differentiated cyto-
logically from TCCs that arise within the prostate.
Tumors of the Urogenital System
Transitional Cell Carcinomas
TCCs may be located in the bladder, urethra, ureter, prostate, or
vagina. Needle aspiration of tumor tissue is avoided to prevent
potential seeding of tumor cells along the needle tract. Trau-
3
matic catheterization of the bladder and prostatic washes are the
preferred means of obtaining cytologic specimens. Cells from a
TCC are individualized round cells with some cells forming
cohesive sheets and clusters. Criteria of malignancy typically are
prominent and include marked anisocytosis and anisokaryosis;
variation in N:C ratios; marked basophilia; coarse chromatin pat-
terns; and variation in nucleolar size, shape, and number (see Fig.
7.4B). Multinuclearity is common. Large circular eosinophilic or
magenta granular inclusions, representing accumulations of gly-
• Fig. 7.12 Fine-needle aspirate of a mammary adenocarcinoma. Inset: cosaminoglycans, occasionally are found in the cytoplasm, but this
Signet-ring cell. feature is not pathognomonic for TCCs (Fig. 7.14). Moderately

• Fig. 7.14 Cells from a transitional cell carcinoma of the prostate. The
• Fig. 7.13 Fine-needle aspirate of a perianal adenoma with characteristic arrow indicates a cytoplasmic eosinophilic inclusion that represents an
hepatoid cells (left) and reserve cells (right). accumulation of glycosaminoglycans.