DCIS is a premalignant condition characterized by proliferation of neoplastic cells within the ducts with intact myoepithelial cell layer and when there is a breach in myoepithelial cell layer it indicates invasion and in both these condition treatment protocols and prognosis is different. Myoepithelial markers can be used to identify breach and hence invasion.
To identify DCIS with microinvasion using SMA, calpopin and p63 by IHC.
This is a retro-prospective observational study with study population of 100 conducted in the department of pathology, Basavatarakam Indo-American cancer hospital and research institute over a period of one year from January 2015 to December 2016 as per inclusion criteria. Suspected cases of DCIS with microinvasion and focal invasion on H&E sections by morphological features is identified. Panel of IHC markers with SMA, calponin and p63 on the suspected cases is performed and efficiency of IHC markers with H&E in detecting microinvasive and focal invasive component is compared. The sensitivity and specificity of IHC markers studied.
The three groups i.e. DCIS, DCIS with microinvasion and DCIS with invasion constitutes 22%, 7% and 71% respectively.
Comparative retrospective analysis of the three groups revealed no difference in age, site whereas mammographically BIRADS IVA is more commonly seen in DCIS group constituting 63.6% cases and BIRADS IVC is seen most commonly in DCIS with microinvasion and DCIS with invasion group each constituting 57.1% and 57.7% respectively.
The most common type of DCIS in pure DCIS group is non comedo necrosis type constituting 59% cases and intermediate nuclear grade constituting 54.5% cases, whereas DCIS with microinvasion and DCIS with invasion group has comedo necrosis type as the most common DCIS each constituting 71.4% and 83% cases and high nuclear grade constituting 71.4% and 84.5% respectively.
The statistical analysis of immunohistochemical markers is done by ROC curve analysis which show that area under the curve for SMA, p63 and calponin are 0.634, 0.596, 0.688 respectively. This indicates that diagnostic accuracy is more for calponin than SMA and p63.
Sensitivity of SMA, calponin and p63 are 91.30%, 90.90%, 68.18% respectively whereas specificity are 23.7%, 87.17%, 98.7% respectively.
DCIS with microinvasion is a very rare entity and in the present study constituting 7% of total cases of DCIS with suspicious foci of invasion which is comparable to the literature.
Morphology alone could not distinguish DCIS with microinvasion from DCIS with focal invasion. This was resolved by IHC for myoepithelial markers. This highlights the role of IHC with myoepithelial markers for detecting micro or focal invasion from pure, albeit extensive DCIS and these observations have direct impact on therapeutic decisions. Out of all markers used in present study i.e. SMA, calponin and p63, calponin has the highest sensitivity and p63 has the highest specificity. Hence this panel of IHC markers can be used to identify microinvasion/ focal invasion in morphologically suspicious biopsies.