CYTOLOGICAL AND ARCHITECTURAL HETEROGENEITY IN DUCTAL CARCINOMA IN-SITU OF THE BREAST

Aim-The traditional architecture based classification system of ductal carcinoma in situ (DCIS) has been criticised on the grounds that indi vidual lesions often show more than one pattern resulting in a large m ixed category. New DCIS classification systems have emphasised the imp ortance of cytological grade, which is reputed to be more uniformly ex pressed throughout a lesion. This study investigates the hypothesis th at cytological heterogeneity is less common than architectural heterog eneity within DCIS lesions. Methods-121 cases of DCIS were graded as p oorly, intermediately, or well differentiated according to a recently developed classification system that employs cytonuclear morphology as the major diagnostic criterion. Cases were categorised as pure when o nly one grade was present and as mixed if more than one grade was obse rved. Architecturally the cases were classified as solid, cribriform, micropapillary, or papillary and were described as pure if only one ar chitectural pattern was present and as mixed if more than one pattern was seen. The incidence of cytological heterogeneity was compared with that of architectural heterogeneity. The presence of necrosis was ass essed as an independent parameter and the relation to DCIS grade evalu ated. Results-Using the cytology based classification system 102 cases (84%) were classified as pure (65 poorly differentiated, 25 intermedi ately differentiated, and 12 well differentiated) and 19 cases (16%) a s mixed. Extensive necrosis was observed in 61 (50%) cases and was clo sely correlated to DCIS grade. Architecturally 46 cases (38%) were cla ssified as pure (38 solid, 5 cribriform, 2 micropapillary, and 1 papil lary) and 75 (62%) as mixed. Conclusions-Cytological heterogeneity is much less common than architectural heterogeneity in DCIS lesions. The assessment of cytonuclear morphology is therefore likely to provide m ore consistent information about DCIS, particularly in small biopsy sp ecimens where only part of the lesion may be available for examination .