DCIS grading schemes and clinical implications

The frequency with which ductal carcinoma in situ (DCIS) is detected has in creased greatly since the introduction of mammographic screening. The numbe r of treatment options has also increased and mastectomy has been extensive ly replaced by local excision with or without radiotherapy. DCIS is general ly unicentric, as evidenced by the rarity with which it is bilateral and th e location of recurrences at the site of previous surgery. Complete excisio n is thus curative but assessing adequacy of excision is beset with signifi cant technical problems and consequently margin involvement does not correl ate very well with the presence of residual disease in the breast or the de velopment of clinical recurrence. Lesion size is related to recurrence but is also often difficult to measure. At the histological level, DCIS is a he terogeneous group of proliferations varying in cytological and architectura l features, some of which are related to clinical outcome. The traditional method of classification was by growth pattern but was found to lack reprod ucibility and prognostic power. As a consequence, several new classificatio ns have been proposed in recent years. Some have been assessed more rigorou sly than others in terms of the consistency with which they can be applied and their ability to predict clinical outcome. There is strong evidence, ho wever, that nuclear grade is the best predictor of recurrence and the time scale over which it is likely to occur although presently it can be determi ned with only fair to moderate consistency. Necrosis is also a useful featu re when used in combination with nuclear grade, but specifically recognizin g a comedo pattern appears to have little clinical value and is associated with significant diagnostic inconsistency. No histological features to date have been found to predict the development of invasive disease. Histologic al assessment alone is insufficient to determine how patients with DCIS sho uld be managed, which should also take account pathological assessment of e xcision margins and lesion size as well as radiological and clinical featur es.