3.a.i Low grade squamous intraepithelial lesion (LSIL)

Low grade squamous intraepithelial lesion (LSIL)

Low grade squamous intraepithelial lesion (LSIL)

Low grade squamous intraepithelial lesion (LSIL)

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Low grade squamous intraepithelial lesions (LSIL) of the cervix are HPV-induced dysplastic changes, most of which are induced by oncogenic HPV types (only a few are induced by the non-oncogenic HPV, namely type 11). Classically, LSILs are characterized by the presence of koilocytes, which are HPV-infected cells showing increased nuclear size, hyperchromasia, irregular nuclear membrane, coarse chromatin, cytoplasmic halo and possibly bi/multinucleation. A fully developed classic LSIL is easily recognized by most pathologists (Fig.1). The koilocytic nuclear changes can often be suspected at low power magnification because of the increased nuclear size and hyperchromasia, which contrast with the surrounding epithelium, and are confirmed at high power magnification. Whenever the LSIL shows more discrete cytological changes (Fig.2) or when it is superimposed on squamous metaplasia (Fig. 3), it can be very challenging to diagnose and there may be important inter-observer and intra-observer variations regarding the diagnosis. Careful observation of nuclear features will help to establish the diagnosis of LSIL. Distinguishing discrete LSIL changes from reactive squamous epithelium is also challenging, however reactive epithelium will not show variation in nuclear size or shape or nuclear membrane irregularity. The presence of nucleoli and conspicuous intercellular bridges due to the presence of intercellular edema are features more in keeping with reactive changes. Correlation with a concurrently submitted paptest may also reveal to be very useful.

To learn more about how to diagnose challenging cases of LSIL, take a look at our tutorial on squamous lesions of the cervix (coming soon!).