Page 153 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

132 PART II Diagnostic Procedures for the Cancer Patient

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• Fig. 7.7 Fine-needle aspirate of a basal cell tumor (trichoblastoma). Note • Fig. 7.8 Fine-needle aspirate of an anaplastic colonic carcinoma. The
the monomorphic population of cohesive cells aligned in rows. tumor cells have high N:C ratios and are sometimes individualized.

those described in the cytopathologist’s complete report and by
considering the information obtained from other diagnostic tests.
Confidence in cytologic interpretation is based on the qual-
ity of the specimen, the completeness of the clinical information
provided, and the experience of the cytopathologist. Terms that
express the degree of certainty, such as “consistent with,” “diagnos-
tic for,” “cannot rule out,” “probable,” and “possible,” may be used
6
and interpreted differently by cytopathologists and clinicians. If
the certainty of an interpretation or diagnosis is unclear, the cli-
nician should consult the cytopathologist. Correlations between
cytologic and histologic interpretations or diagnoses are highly
variable, depending on tissue types, disease processes, and meth-
ods of collection and preparation.

Epithelial, Mesenchymal, and Discrete Round
Cell Tumors

The ability to identify specific tumor types by cytologic evalua- • Fig. 7.9 Fine-needle aspirate of a basal cell tumor (trichoblastoma) in
tion can aid in treatment planning and prognostication. Even if a which the cells are heavily pigmented.
specific diagnosis cannot be made, classification of the tumor as
an epithelial, mesenchymal, or discrete round cell neoplasm can longer have intercellular junctions and appear as discrete round
provide sufficient information to formulate a differential diagnosis cells (Fig. 7.8). Determining the tissue of origin in these cases
and plan additional diagnostic procedures. is difficult, and histologic evaluation, with or without immuno-
histochemical analysis, is necessary to define the specific tumor
Tumors of Epithelial Tissues type.
Tumors derived from epithelial tissue comprise the largest cate- Tumors of Adnexa in Skin with Basilar or Sebaceous Cells
gory of neoplasms and include tumors of epithelial surfaces, such Differentiating among adnexal tumors of skin by cytologic eval-
as the skin and respiratory, gastrointestinal, and urogenital tracts, uation may be difficult when identifying features are absent or
and tumors of glands and organs. Given their diverse origin, the when multiple cell types are present. Some of these tumors have a
cytomorphologic appearance of these neoplasms can be highly large component of basilar cells that are small cuboidal or round
variable; however, some features are shared by most epithelial cells with high N:C ratios and are arranged in tightly cohesive
tumors. Epithelial cells have intercellular junctions that connect sheets or in palisading rows (see Fig. 7.7). Nuclei are uniformly
the cells to each other and do not elaborate extracellular matrix. round with condensed to reticular chromatin, and nucleoli are
Therefore cells exfoliate well, resulting in highly cellular speci- indistinct or appear as a small single nucleolus. The cytoplasm is
mens, and are arranged in cohesive sheets or clusters in cytologic lightly basophilic and may contain black melanin granules (Fig.
smears (Fig. 7.7). The cytoplasmic borders of individual cells 7.9). Tumors that originate from the hair follicle and matrical
typically are distinct, but this can vary in certain types of tumors. cysts often have a central cystic space filled with mature squamous
Poorly differentiated epithelial tumors have few or no identify- cells, keratin flakes, or keratin debris, and this material may be
ing features and tend to be round cells with moderate-to-high aspirated when the mass is sampled. Tumors with sebaceous dif-
N:C ratios and basophilic cytoplasm. In some cases, the cells no ferentiation contain clusters of large round cells filled with oily