[216] Distinction of Pleomorphic from Classical Lobular Carcinoma In Situ: Proposition for a Minimum Diagnostic Criteria Based on Morphology

BC Ho, AH Lee, IO Ellis. Nottingham City Hospital, Nottingham, United Kingdom

Background: Recent data have shown no consistent immunophenotypic or genetic differences between pleomorphic LCIS (PLCIS) and classical LCIS (CLCIS), yet different management strategies are emerging following their distinction. Further, consensus criteria aiding distinction of PLCIS from CLCIS are lacking. In this study, we aimed to compare the morphologic features of PLCIS and CLCIS to determine if differences exist which could assist routine classification.
Design: 49 lesions {23 PLCIS and 26 classical lobular neoplasia (CLN)} in 45 women (4 had PLCIS and CLCIS) diagnosed in consultation from Jan 2005 to September 2009 were reviewed. Parameters examined were cellular dyscohesion, nuclear diameter, nuclear size variation, nucleolar presence and prominence (easily visible at x10 objective), number of mitoses per 10 high power fields (HPF), presence of necrosis and nuclear features of associated invasive carcinoma.
Results: All PLCIS lesions showed acinar distension by dyscohesive tumour cells with nuclear diameters ranging from 2-6x that of a small lymphocyte, with the following distribution: <2.5x (n=1), 2.5-<3x (n=8), 3-<4x (n=8), 4x and above (n=6). A 2-3 fold nuclear size variation was noted in all lesions of PLCIS. Nucleoli were observed in every PLCIS lesion; and were prominent in 15/23 lesions. Mitotic activity was detected in 20/23 (87%) PLCIS lesions, with an average mitotic index of 2.3/10 HPF (range 1-7). Tumour necrosis was present in 61% PLCIS lesions. 7 PLCIS lesions showed adjacent invasive lobular carcinoma; in six, both invasive and in situ tumour cells showed identical nuclear morphology whereas in one, invasive tumour cells showed significantly smaller nuclei (2x that of lymphocyte) than the in situ tumour cells (4x that of lymphocyte). In contrast, all CLN lesions exhibited nuclear diameters 1-2x that of a small lymphocyte and between 1-2x nuclear size variation (2x variation in some cells noted in 3 CLN lesions). Nucleoli (none prominent) were seen in 13 CLN lesions. None of the CLN lesions showed necrosis and two disclosed mitotic activity (1 mitosis/10 HPF in each).
Conclusions: PLCIS can reliably be distinguished from CLCIS on morphologic grounds, with parameters such as nuclear size and variation, presence of necrosis and mitotic activity being most helpful. We propose that LCIS composed of dyscohesive cells with at least 2x nuclear size variation and nuclear diameters greater than 2x that of a small lymphocyte as meeting the minimum criteria for a designation of 'pleomorphic' LCIS.
Category: Breast

Monday, March 22, 2010 8:45 AM

Platform Session: Section C, Monday Morning


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