Page 36 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Cytological Criteria of Malignancy
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4.2 Nuclear Criteria
VetBooks.ir • Anisokaryosis and macrokaryosis/karyomegaly

Anisokaryosis (nuclear size variation) and macrokaryosis/karyomegaly (presence of excep-
tionally large nuclei) are considered significant when moderate to marked, although this
should be interpreted in the context of the characteristics of the tissue of origin.
• Asynchronous nucleus to cytoplasm maturation
A marked variation of this ratio from the normal cell counterpart is considered an abnormal
finding.
• Multinucleation
Multinucleation is particularly significant when nuclei within the same cell are variably sized and
in the presence of odd numbers of nuclei per cell. Certain non-neoplastic cell types are typically
multinucleated (e.g. megakaryocytes, osteoclasts, multinucleated giant inflammatory cells).
• Nucleoli
Nucleoli are nuclear substructures assigned to produce ribosomes and are considered a hall-
mark of malignancy when they become prominent, multiple, irregularly shaped (e.g. angular,
elongated, etc.) and variably sized (anisonucleosis). Some non-neoplastic cells normally
contain visible nucleoli (e.g. hepatocytes). Nucleoli may also be spuriously prominent in
cells that are either ruptured or under-stained.
• Coarse and/or variable chromatin pattern
The cytological evaluation of the chromatin should always be related to the pattern ob-
served in the non-neoplastic counterpart.

(A) (B)

(C) (D)

Fig. 4.1. Criteria of malignancy. (A) Anisokaryosis and nuclear moulding. (B) Multinucleation, nuclear fragmenta-
tion and large prominent nucleoli. (C) Irregular nuclear shape. (D) Atypical mitosis.