Pleomorphic Lobular Carcinoma: Immunohistochemistry Study of 27 Cases.
LaKeta Monhollen, Carl Morrison, Foluso Ademuyiwa, Remeela Chandrasekhar, Gregory Wilding, Thaer Khoury. Roswell Park Cancer Institute, Buffalo, NY
Background: Analysis of gene expression profiling data on breast cancers has revealed “molecular subclasses” that may have prognostic significance. “Basal type” has been proposed to be present in pleomorphic lobular carcinoma (PLC). The purpose of this study was to evaluate the molecular subtypes of PLC by IHC and to explore the incidence of GCPD-15 and mammaglobin expression.
Design: Cases were collected from the clinical database and pathology department search engine in Roswell Park Cancer Institute from 1995 to 2010. Cases were either in house or referred from another hospital. Histologic features were reviewed including SBR grade, percentage of grade 3 nuclei (>10% was required to consider tumor pleomorphic). Cases with available tissue blocks were constructed in tissue microarray (TMA) blocks (n= 27). E-cadherin, estrogen receptor (ER), progesterone receptor (PR), cytokeratin 5/6, CAM, GCPD-15, mammaglobin, CD117, vimentin, EGFR, p53 and HER2 by fluorescence in situ hybridization were performed on the TMA slides. ER and PR were scored using Allred scoring system. All other markers were scored from 0 to 3; >1 was considered positive. Statistical analyses to assess the significance of the difference between two correlated proportions based on the same sample were performed using the exact McNemar's test.
Results: There were 3 (11.1%) cases of HER2 type, 5 (18.5%) of triple negative type and 10 (37%) of luminal type. Overall, basal type markers were as follows: CD117 in 4 of 24 (16.7%), CK5/6 in 4 of 26 (15.4%), EGFR 1 of 27 (3.7%) and vimentin 1 of 26 (3.8%). Among the cases that had all the available markers (n=22), only two (9.1%) cases were positive for at least two of the basal type markers, one for vimentin, p53 and CD117 and one for CK5/6, EGFR and p53. The latter was triple negative. Moreover, PLC appears to express mammaglobin (15 of 25 cases) more frequently than GCPD-15 (8 of 25 cases) with borderline significance (p=0.07, McNemar's test).
Conclusions: From this small series, basal type PLC by IHC is rare and HER2 subtype is more common than conventional lobular carcinoma. Although GCPD-15 is traditionally recognized as a sensitive marker for PLC, mammaglobin appears to be more sensitive. Additional studies with larger numbers of cases are needed to validate our data.
Monday, February 28, 2011 1:00 PM
Poster Session II # 53, Monday Afternoon