Page 154 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 7 Diagnostic Cytopathology in Clinical Oncology 133

stains, and cytologic features suggestive of keratinization include
individualization of cells, sharp angular cytoplasmic margins, and
smooth and glassy turquoise cytoplasm. Cells that appear keratin-
VetBooks.ir ized may have small condensed nuclei or absent nuclei, represent-
ing a normal maturational process, but may have a large intact
nucleus with fine-to-reticular chromatin and multiple visible
nucleoli. An immature nucleus concurrent with mature cytoplasm
signifies “asynchronous maturation.” Perinuclear vacuolation or
magenta cytoplasmic inclusions (keratohyaline granules) may
be observed in the more mature squamous cells. Keratinization
within a tumor typically is accompanied by neutrophilic inflam-
mation (Fig. 7.11, inset). Differentiating between SCC and a pri-
mary inflammatory lesion with dysplastic squamous epithelium
can be a cytologic dilemma: in both cases, the cells may have
criteria of malignancy and asynchronous maturation. Location,
appearance of the lesion, and ultimately histologic examination
aid in differentiating inflammatory and neoplastic lesions.
• Fig. 7.10 Fine-needle aspirate of a sebaceous adenoma.
Tumors of Glands
Salivary Gland Tumors
Salivary gland tumors may be composed of ductular cells, secretory
cells, or both. Salivary ductular cells or poorly differentiated secretory
cells resemble basilar epithelial cells with minimal pleomorphism
even when these tumors are malignant; mild-to-moderate anisokary-
osis may be present and nucleoli may be prominent. Tumors with
a predominance of secretory cells include well-differentiated forms
(acinic carcinoma) and more pleomorphic forms. The neoplastic cells
are arranged in 3D clusters, sometimes resembling acini seen histo-
logically, and have moderate and variable N:C ratios. The cytoplasm
contains few-to-many secretory vacuoles of varying sizes. Cells with a
single large vacuole that displaces the nucleus to an eccentric location
may be noted and are referred to as signet-ring cells. In pleomorphic
salivary adenocarcinomas, anisokaryosis and the presence of visible
nucleoli of varying number, shape, and size are typical. Some tumors
may produce mucin, which appears as pale pink or blue material that
aligns surrounding erythrocytes into streaming rows.
• Fig. 7.11 Fine-needle aspirate of a squamous cell carcinoma (SCC). Note Mammary Gland Tumors
the marked anisocytosis and anisokaryosis, variable N:C ratios, perinu- Mammary gland tumors are classified histologically into benign
clear vacuolation, and angular cytoplasmic borders in some cells. Inset: A and malignant tumors based on the type, arrangement, and inva-
neutrophilic infiltrate often accompanies SCC. siveness of neoplastic epithelium and on the presence or absence
of neoplastic and nonneoplastic mesenchymal components. This
appearing vacuoles that partially obscure the small central nucleus classification system cannot be applied to cytologic specimens,
(Fig. 7.10). Necrotic cellular debris may be found in both benign nor can biologic behavior reliably be ascertained by cytology.
and malignant forms of these tumors. Cutaneous basilar epithelial Cytologic specimens from mammary masses may contain ductu-
neoplasms include trichoblastoma, trichoepithelioma, pilomatri- lar cells, secretory cells, mesenchymal cells, or a combination of
coma, feline basal cell tumors, sebaceous epithelioma, apocrine these. Cells from ductular or tubular mammary tumors resemble
ductal adenoma, and others; histologic examination is usually basilar epithelial cells with low-to-moderate N:C ratios and occa-
required to identify the specific type. Fortunately, the majority of sionally contain basophilic granular cytoplasmic inclusions. Pleo-
adnexal tumors are benign. Malignant types are infrequent; some morphic features are mild-to-moderate, even when these tumors
resemble their benign counterparts but have frequent mitoses, are malignant. Tumors of secretory origin have few-to-many cri-
whereas others have pleomorphic features that predict their bio- teria of malignancy, including moderate-to-marked anisocytosis
logic behavior. and anisokaryosis, variably sized secretory vacuoles within the
cytoplasm with some signet-ring formation, and nuclear criteria
Tumors of the Epidermis of malignancy (Fig. 7.12). If present, the mesenchymal compo-
Squamous cell carcinoma (SCC) is the most common malignancy nent may consist of mildly to moderately pleomorphic spindle
of the epidermis; the tumor has varying degrees of differentiation, cells with or without fibrillar magenta extracellular matrix. The
even within a single tumor, and the cytologic specimen may con- spindle cells represent myoepithelial cells or fibroblasts and may
sist primarily of basilar cells, more mature keratinized cells, or both be neoplastic or nonneoplastic. The background of many mam-
(Fig. 7.11). Pleomorphism can be marked, including moderate- mary tumors contains lakes of blue secretory material, vacuolated
to-marked anisocytosis and anisokaryosis, hyperchromasia, and macrophages containing similar material, and low numbers of
marked nuclear atypia. Keratin does not stain with Romanowsky neutrophils. Although biologic behavior is difficult to determine