Neither Brief Formalin Fixation nor Rapid Tissue Processing Impact the Sensitivity of ER Immunohistochemistry in Core Biopsies of the Breast
Victoria Sujoy, Mehrdad Nadji, Azorides R Morales. University of Miami, Jackson Health System and Sylvester Cancer Center, Miami, FL
Background: The ASCO/CAP guidelines for estrogen receptor immunohistochemistry (ER-IHC) recommend a minimum of 8 hour formalin fixation for core breast biopsies. A number of recent publications however, have questioned the supporting evidence for this recommendation (Gown AM; 2009, Ibarra JA et al; 2010, Apple S et al; 2011). In this study we investigated whether brief formalin fixation and rapid tissue processing have negative effects on the sensitivity of the ER-IHC in core biopsies of the breast.
Design: Twenty-two cases of total or partial mastectomy samples were collected within 30 minutes of excision for this study. A 1.0 x 1.0 x 0.2 cm slice of each tumor was removed and further subdivided into five 1.0 x 0.2 x 0.2 cores. The cores were immediately fixed in phosphate buffered formalin solution for different period of times in the following manner: core 1 was fixed for 30 minutes, core 2 for 60 minutes, core 3 for 24 hours, core 4 for one week and core 5 was fixed in parallel with the routine surgical pathology specimens for a period of time between 12 to 48 hours. Cores 1 through 4 were processed in a formalin-free microwave-based rapid tissue processing system (Xpress, Sakura Finetek) while core 5 was processed overnight (10 hours) in a conventional tissue processor (VIP, Sakura Finetek). Immunohistochemistry for ER was performed following heat-induced antigen retrieval using monoclonal antibody ID5 and the FLEX polymer detection systems (Dako). The percentage of positive cells and the intensity of reaction was recorded for all cores.
Results: Of the total of 22 samples, five cases were ER-negative in all five cores. In 17 ER-positive cases, the reaction was present in more than 80-90% of tumor cells in each core. There was no significant differences in intensity of ER-IHC between 30 minutes, 60 minutes, 24 hours and one week formalin fixation (Kappa=0.97). Similarly, no difference was observed in the intensity of reaction between rapidly and conventionally processed tumors.
Conclusions: Brief formalin fixation, as short as 30 minutes, has no deleterious effect on the sensitiviy of ER-IHC in core biopsies of the breast. Furthermore, there is no significant difference between conventional overnight processing and rapid tissue processing in the sensitivity of ER immunostaining. The combination of short fixation time and rapid processing platforms enable the laboratories to significantly decrease the turnaround time for breast core biopsies.
Monday, March 19, 2012 1:00 PM
Poster Session II # 299, Monday Afternoon