Mammary Ductal Carcinoma In Situ: A Fresh Look at Architectural Patterns

Mammary ductal carcinoma in-situ (DCIS), a malignant appearing lesion on cytological and histological grounds, is in fact a non-obligate precancer. DCIS is difficult to manage and is sometimes treated more aggressively than invasive carcinoma. Although most DCIS classifications take into account the architectural growth pattern, when it comes to architecture, the literature is full of contradictory information. We examined 289 breast cancers and found DCIS in 265 of the cases. The majority of the DCIS cases were seen in the setting of invasive cancer and only 9% of the cases represented pure DCIS with no invasive cancer. The DCIS commonly displayed a mixed pattern with micropapillary, cribriform and solid components with the micropapillary type being the rarest, occurring seldom on its own. A continuum of growth with a micropapillary pattern evolving into a cribriform type could be seen in some of the cases. This may explain some of the conflicting information, in the literature, regarding the different architectural types of DCIS. The comedo-pattern of necrosis could be seen in all types of DCIS. We therefore conclude that the study of the determinants of growth pattern in DCIS would be the key to unravelling the diverse, often non-concordant evidence one encounters in the literature. 1. Introduction Classifying and managing DCIS has always been a thorny issue, often dividing various groups of pathologists around the world [1]. Amongst DCIS features, the architectural pattern, its prognostic value, and role in grading DCIS have also been stirring sufficient controversy. The current literature on the subject accepts the existence of 3 major architectural patterns of DCIS, namely, the solid, cribriform, and micropapillary patterns [2]. The clinging or flat type is not universally accepted as fully developed DCIS. It has been variably considered as an early micropapillary DCIS or even a subvariant of the atypical ductal hyperplasia [3]. Other special types of DCIS, such as the apocrine, the endocrine (argyrophilic), and signet ring DCIS, are all defined on histological criteria, rather than architectural pattern and they actually belong to the solid pattern of growth. With respect to grading, it is universally accepted that the nuclear grade is the essential feature, recurring in all classification systems previously proposed and currently in use [4]. An association, albeit inconsistent, exists between the nuclear grade and the architectural growth pattern. It is generally accepted that most micropapillary and cribriform in situ carcinomas are of low