The categories
Unit 7 of 8
Place a patch in C1 to C5, and say the risk of malignancy and the management that follows.
Five categories, each with a definition, a risk of malignancy and a management line. Learn them as a set: the risk is what turns a category into a decision, and the management line is that decision.
The grey zone is between C2 and C4, and it is a real overlap rather than a failure of nerve. C3 exists because proliferative lesions and low grade carcinomas share features. C4 exists because a smear can carry malignant features without enough of them to state a diagnosis.
The drills here ask for the full five way call on both stains, then pair a patient's two slides so you can see whether your category moves when the stain changes.
The five categories, quoted
C1 Insufficient or inadequate
The smears are too sparsely cellular or too poorly smeared or fixed to allow a cytomorphological diagnosis.
- Risk of malignancy
- 2.6 to 4.8 percent
- Management
Review clinical and imaging findings; if imaging indeterminate or suspicious, repeat FNAB or proceed to CNB.
A cytologist would look for
seven tissue fragments each consisting of 20 or more epithelial cells
pus consistent with an abscess
proteinaceous background consistent with cyst contents
C2 Benign
A benign breast FNAB diagnosis is made in cases that have unequivocally benign cytological features, which may or may not be diagnostic of a specific benign lesion.
- Risk of malignancy
- 1.4 to 2.3 percent
- Management
If the triple test is benign, no further biopsy is required; if clinical or imaging findings are suspicious, repeat FNAB or proceed to CNB.
A cytologist would look for
predominantly large cohesive three-dimensional tissue fragments and flat mono-layered sheets
evenly spaced ductal epithelial cells with myoepithelial cells creating a bimodal pattern
bare bipolar nuclei representing stripped myoepithelial nuclei, in the background
C3 Atypical
The presence of cytological features seen predominantly in benign processes or lesions, but with the addition of some features that are uncommon in benign lesions and which may be seen in malignant lesions.
- Risk of malignancy
- 13 to 15.7 percent
- Management
Repeat FNAB if the atypia is considered likely to be due to a technical issue; if good material is available and atypical, repeat FNAB or preferably proceed to CNB.
A cytologist would look for
overlapping cytological features between proliferative breast lesions, such as usual epithelial hyperplasia, intraductal papillomas and fibroadenomas, and low-grade in situ lesions and low-grade invasive carcinomas
poor FNAB technique may result in low cellularity and obscuring blood or ultrasound gel, overly forceful smearing causing crush artefact and dispersal
C4 Suspicious for malignancy
The presence of some cytomorphological features, which are usually found in malignant lesions, but with insufficient malignant features, either in number or quality, to make a definitive diagnosis.
- Risk of malignancy
- 84.6 to 97.1 percent
- Management
CNB is mandatory.
A cytologist would look for
highly cellular smears, a pattern of large tissue fragments showing cribriform, micropapillary or papillary architecture
variable but often marked increase in dispersed single cells showing mild to moderate nuclear atypia
greatly reduced number or total lack of myoepithelial cells
C5 Malignant
An unequivocal statement that the material is malignant, and the type of malignancy identified should be stated whenever possible.
- Risk of malignancy
- 99 to 100 percent
- Management
If the triple test is concordant, proceed to definitive management; if discrepant, CNB or excision biopsy is mandatory.
A cytologist would look for
high cellularity, prominent dispersal of single cells
crowded tissue fragments with overlapping nuclei
nuclear enlargement, anisonucleosis, pleomorphism of the nuclear margin, size and chromatin, hyperchromasia and prominent nucleoli
a greatly reduced number or total lack of myoepithelial cells associated with the epithelial tissue fragments, and scant or absent bare bipolar nuclei
Rapid on-site evaluation
ROSE of the FNAB direct smears provides a reduction in insufficient rates, as well as a reduction in atypical and suspicious rates, and a concomitant increase in benign and malignant diagnoses.
Experienced personnel performing the FNAB should aim for less than a 5 percent insufficient rate, particularly if utilizing ROSE, while a rate of 10 to 20 percent requires review.
CNB should be regarded as a complementary rather than replacement test.
The worked example
Loading the case library.
About 20 trials, 5 to 8 minutes. You can stop at any point.