Diagnostic Cytology
Fig. 8.106 Microinvasive cancer: syncytial aggregate of epithelial cells
with indistinct cell borders. Irregular distribution of nuclear chromatin and
nucleoli varying in size and shape (Papanicolaou x OI).
Evidence o f Tissue Destruction
Obviously related to the depth of invasion, evidence of tissue
destruction was considerably less frequently found than in overt
invasive cancer.194,210 Related to the depth of invasion and the
amount of tissue destruction by the invading process, cellular
features are more reminiscent of either carcinoma in situ or
frankly invasive cancer. In a series of 52 cases of proven micro-
invasive cancer, Ng and colleagues found cellular characteristics
of microinvasive cancers with an epithelial infiltration of 0.1-
mm to resemble those of carcinoma in situ and dysplasia,
whereas those in cases of microinvasion of 3.1-5.0 mm were
more reminiscent of frankly invasive cancer.210 Cellular features
consistent with microinvasive cancer were found to be most
distinctive with a depth of invasion between 2 and 3 mm.
Key features of microinvasive squamous carcinoma
• Round to oval cells arranged predominantly in
syncytial aggregates;
• Cyanophilic cytoplasm with relative increase in
cytoplasmic volume;
• Round to oval nuclei with considerable size variation;
Fig. 8.107 Microinvasive cancer. Round-to-oval nuclei with irregular
distribution of coarsely granular hyperchromatic nuclear chromatin and
pleomorphic nucleoli (Papanicolaou x OI).
• Nuclear chromatin fine to coarsely granular with
uneven distribution;
• Micronucleoli are typically present; macronucleoli are
• Tumor diathesis may be present, but typically less
than in invasive carcinoma (dependent on depth of
invasion); and
• N/C is lower than in carcinoma in situ.
Ng and Reagan state that on the basis of cellular characteristics,
the diagnosis of microinvasive cancer can be made accurately
and reproducibly in a high proportion of cases.5,194 From 56
cases of proven microinvasive cancer, 80% were correctly recog-
nized as microinvasive in the cellular samples. In a review study
of 100 cases obtained from patients with lesions associated with
cancer of the cervix, correct interpretation was made in 97% of
cases of carcinoma in situ, in 87% of cases of microinvasive can-
cer, and in 97% of cases of clear-cut cancer. Nguyen reviewed
42 cases of histologically proven microinvasive squamous cell
carcinomas with invasion of less than 3 mm.211 At review, micro-
invasion could be suggested on the basis of cellular features
in approximately 60% of cases. Cytologic prediction was 14%
in cases with stromal invasion less than 1 mm; it increased to
73 and 88% when stromal invasions were up to 2 and 3 mm,
respectively, in depth.
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