- Email: [email protected]
neu immunostaining in pancreatic carcinoma
CORRESPONDENCE
from policies that have been evolving over more than 3 years from an ad hoc committee of the Biologic Stain Commission, which includes FDA representatives, pathologists, and commercial spokespersons. The FDA’s mandate is clear, but its implementation is not. For example, in vitro diagnostic devices in use before the enactment of the regulatory legislation are exempt. Does one interpret immunostains inclusively to be exempt because immunofluorescence long predated the statutes? Furthermore, there is gradation of premarketing FDA approval in relation to the perceived degree of direct linkage to clinical consequences. Presently, a petition requesting immunoreagents for anatomic pathology to be classified at an intermediate level as “class II devices” is being drafted for FDA consideration. Such classification would require independent verification of claimed specificity and sensitivity of the reagents, but not proven clinical efficacy. Published studies, such as that of Utz and Swerdlow’, would be acceptable data for FDA consideration for class II device approval. Additionally, the FDA must also weigh potential adverse effects on current medical care in implementing restrictions. Some FDA representatives are themselves pathologists who fully understand the degree to which diagnostic practice has come to depend on immunostains, many of which are not approved. Therefore, the anticipated FDA plan calls for requirement of premarketing approval, but with a “grace period” during which manufacturers and distributors can accrue data and ap ply for approval. It should be pointed out that several brands of test kit for carcinoembryonic antigen serum assay acquired the rigorous “class III device” FDA approval in 1983 and 1984. And yet, as pointed out in my editorial: 10 years later extensive clinical studies indicate that these tests are not clinically efficacious after all. Most importantly, even the most exhaustive independent testing of an immunoreagent cannot assure its accurate interpretation in the complexities of any one particular case. Whether the informational source is a package insert or a journal article, application of immunostaining to diagnostics is ultimately the responsibility of the pathologist. PETER M. BANKS, MD Professor and Director of Anatomic Pathology The University of Texas Health Science Center at San Antonio San Antonio, TX
1. UtzGL, Swerdlow SH: Distinction of follicular hyperplasia from follicular lymphoma in B.5-fixed tissues: Comparison of MT2 and bcl-2 antibodies. HUM PATHOL24:11551158,1993 2. Banks PM: When is a new diagnostic method established? HUM PATHOL 24:1153-1154,1993
HER2/neu lmmunostaining Carcinoma
in Pancreatic
TO tb Editor:-The article by Drs. Yamanaka et al’ in the October 1993 issue of HUMANPATHOLOGY reports immunoreactivity for HERS/neu in 45% of pancreatic cancers in contrast to previous studies that found overexpression of this oncoprotein in a much lower percentage (2%) of such cancers.* It seems from their illustrations that Yamanaka et al have interpreted cytoplasmic staining as indicating overexpression of ~185. This may explain the discrepancy with the literature and my own (unpublished) experience with carcinoma of the pancreas and HER2/neu immunostaining. HER2/neu gene product is a transmembrane protein and its function is in great part dependent on its correct localization at the cell membrane. It has been known for some time
that only membrane staining correlates with HER2/neu gene amplification.” Moreover, only membrane staining is accompanied by raised ~185 levels as measured by Western blotting.“16.’For these reasons the accepted current practice is to disregard the cytoplasmic staining and to consider positive only those tumors showing clearly discernible membrane staining.’ It seems well established that the principal mechanism leading to overproduction of p185 in neoplasms, regardless of site of origin, is gene amplification. A small percentage of breast cancers may show membrane immunostaining for HER2/neu without evidence of gene amplification. However, these are frequently oligocellular tumors where the DNA extract may have been h&avily contaminated with stromal cell DNA.’ Therefore, the finding of a high proportion of pancreatic cancers overexpressing ~185 in the absence of gene amplification is surprising. It should be noted that increased levels of HER2/neu messenger RNA (mRNA) do not necessarily mean higher synthesis of the expected molecule. A molecule of smaller size-and unknown function-than the normal HER2/neu gene product is often found in cells lacking membrane localization by immunohistochemistry.” Thus, without independent validation of increased ~185 synthesis-ie, by Western blottingthe significance of cytoplasmic staining for HER2/neu in pancreatic cancer is not clear. Lastly, most studies of breast cancer have shown a higher proportion of HER2/nmpositive tumors among those with worse nuclear or histological grade. It seems odd that in this series the highest incidence of HER2/neu immunoreactivity was found in the better-differentiated tumors. It is hard to understand why the expression of HER2/neu under these circumstances “gives pancreatic cancer cells a growth advantage” as suggested by the authors. HECTOR BATTIFORA, MD City of Hope National Medical Center Duarte, CA 1. Yamanaka Y, Friess H, Kobrin MS, et al: Overexpression of HER2/nac oncogene in human pancreatic carcinoma. HUM PATHOL24:1127-I 134,‘1993 2. Hall PA, Hughes CM, Staddon SL, et al: The c-o6B2protc-oncogene in human pancreatic cancer. J Pathol 161:195200,1990 3. Machin L. Ashlev S, Dean C. et al: Immunohistochemical distributio: of c-erbB2-like immunoreactivity in tissues-Biological and clinical significance with particular respect tn breast cancer. Diagn Oncol 1:209-217.1991 4. Slamon 91, Press MF, Godolphin W, et al: Studies of the HER-l/neu proto-oncogene in human breast cancer, in Furth M, Greaves M (eds): Cancer $;e8y Spring Harbor, NY, Cold Spring Harbor Laboratoty Press, 1988, pp. 5. Battifora H, Gaffey M, Est$ban JM, et al: Immunohistochemical assay of neu/cerbB-2 oncogene product m paraffin-embedded tissues in early breast cancer. Retrospective follow-up study of 245 stage I and II cases. Modem Pathol 4:466474. 1991 6. Kerns 5JM, Pence JC, Huper G, et al: wrbB2 Expression in breast cancer detected by immunoblotting and immunohistochemistty. 1 Histochem Cytochem 38:182%1830,1990 7. Molina R, Ciocca DR. Tandon AK. et al: Exnression of HER-~/W oncoprotein in human breast cancer: A comparison of~mmunohistochen&l and Western blot techniques. Anticancer Res 12:1965-1972,1992
The above letter was referred to the authms of the article in guestion, who offer the following reply: To the Editor:-We are grateful to Dr Battifora for his interest and thoughtful comments about our article dealing with HER2 (c+erbE-Z/neu)overexpression in human pancreatic carcinomas. We agree that HER2 overexpression in human breast cancers is often defined immunohistochemically by the presence of membrane HER2 immunostaining, which is frequently correlated with amplification of the HER2 gene. We
549
from policies that have been evolving over more than 3 years from an ad hoc committee of the Biologic Stain Commission, which includes FDA representatives, pathologists, and commercial spokespersons. The FDA’s mandate is clear, but its implementation is not. For example, in vitro diagnostic devices in use before the enactment of the regulatory legislation are exempt. Does one interpret immunostains inclusively to be exempt because immunofluorescence long predated the statutes? Furthermore, there is gradation of premarketing FDA approval in relation to the perceived degree of direct linkage to clinical consequences. Presently, a petition requesting immunoreagents for anatomic pathology to be classified at an intermediate level as “class II devices” is being drafted for FDA consideration. Such classification would require independent verification of claimed specificity and sensitivity of the reagents, but not proven clinical efficacy. Published studies, such as that of Utz and Swerdlow’, would be acceptable data for FDA consideration for class II device approval. Additionally, the FDA must also weigh potential adverse effects on current medical care in implementing restrictions. Some FDA representatives are themselves pathologists who fully understand the degree to which diagnostic practice has come to depend on immunostains, many of which are not approved. Therefore, the anticipated FDA plan calls for requirement of premarketing approval, but with a “grace period” during which manufacturers and distributors can accrue data and ap ply for approval. It should be pointed out that several brands of test kit for carcinoembryonic antigen serum assay acquired the rigorous “class III device” FDA approval in 1983 and 1984. And yet, as pointed out in my editorial: 10 years later extensive clinical studies indicate that these tests are not clinically efficacious after all. Most importantly, even the most exhaustive independent testing of an immunoreagent cannot assure its accurate interpretation in the complexities of any one particular case. Whether the informational source is a package insert or a journal article, application of immunostaining to diagnostics is ultimately the responsibility of the pathologist. PETER M. BANKS, MD Professor and Director of Anatomic Pathology The University of Texas Health Science Center at San Antonio San Antonio, TX
1. UtzGL, Swerdlow SH: Distinction of follicular hyperplasia from follicular lymphoma in B.5-fixed tissues: Comparison of MT2 and bcl-2 antibodies. HUM PATHOL24:11551158,1993 2. Banks PM: When is a new diagnostic method established? HUM PATHOL 24:1153-1154,1993
HER2/neu lmmunostaining Carcinoma
in Pancreatic
TO tb Editor:-The article by Drs. Yamanaka et al’ in the October 1993 issue of HUMANPATHOLOGY reports immunoreactivity for HERS/neu in 45% of pancreatic cancers in contrast to previous studies that found overexpression of this oncoprotein in a much lower percentage (2%) of such cancers.* It seems from their illustrations that Yamanaka et al have interpreted cytoplasmic staining as indicating overexpression of ~185. This may explain the discrepancy with the literature and my own (unpublished) experience with carcinoma of the pancreas and HER2/neu immunostaining. HER2/neu gene product is a transmembrane protein and its function is in great part dependent on its correct localization at the cell membrane. It has been known for some time
that only membrane staining correlates with HER2/neu gene amplification.” Moreover, only membrane staining is accompanied by raised ~185 levels as measured by Western blotting.“16.’For these reasons the accepted current practice is to disregard the cytoplasmic staining and to consider positive only those tumors showing clearly discernible membrane staining.’ It seems well established that the principal mechanism leading to overproduction of p185 in neoplasms, regardless of site of origin, is gene amplification. A small percentage of breast cancers may show membrane immunostaining for HER2/neu without evidence of gene amplification. However, these are frequently oligocellular tumors where the DNA extract may have been h&avily contaminated with stromal cell DNA.’ Therefore, the finding of a high proportion of pancreatic cancers overexpressing ~185 in the absence of gene amplification is surprising. It should be noted that increased levels of HER2/neu messenger RNA (mRNA) do not necessarily mean higher synthesis of the expected molecule. A molecule of smaller size-and unknown function-than the normal HER2/neu gene product is often found in cells lacking membrane localization by immunohistochemistry.” Thus, without independent validation of increased ~185 synthesis-ie, by Western blottingthe significance of cytoplasmic staining for HER2/neu in pancreatic cancer is not clear. Lastly, most studies of breast cancer have shown a higher proportion of HER2/nmpositive tumors among those with worse nuclear or histological grade. It seems odd that in this series the highest incidence of HER2/neu immunoreactivity was found in the better-differentiated tumors. It is hard to understand why the expression of HER2/neu under these circumstances “gives pancreatic cancer cells a growth advantage” as suggested by the authors. HECTOR BATTIFORA, MD City of Hope National Medical Center Duarte, CA 1. Yamanaka Y, Friess H, Kobrin MS, et al: Overexpression of HER2/nac oncogene in human pancreatic carcinoma. HUM PATHOL24:1127-I 134,‘1993 2. Hall PA, Hughes CM, Staddon SL, et al: The c-o6B2protc-oncogene in human pancreatic cancer. J Pathol 161:195200,1990 3. Machin L. Ashlev S, Dean C. et al: Immunohistochemical distributio: of c-erbB2-like immunoreactivity in tissues-Biological and clinical significance with particular respect tn breast cancer. Diagn Oncol 1:209-217.1991 4. Slamon 91, Press MF, Godolphin W, et al: Studies of the HER-l/neu proto-oncogene in human breast cancer, in Furth M, Greaves M (eds): Cancer $;e8y Spring Harbor, NY, Cold Spring Harbor Laboratoty Press, 1988, pp. 5. Battifora H, Gaffey M, Est$ban JM, et al: Immunohistochemical assay of neu/cerbB-2 oncogene product m paraffin-embedded tissues in early breast cancer. Retrospective follow-up study of 245 stage I and II cases. Modem Pathol 4:466474. 1991 6. Kerns 5JM, Pence JC, Huper G, et al: wrbB2 Expression in breast cancer detected by immunoblotting and immunohistochemistty. 1 Histochem Cytochem 38:182%1830,1990 7. Molina R, Ciocca DR. Tandon AK. et al: Exnression of HER-~/W oncoprotein in human breast cancer: A comparison of~mmunohistochen&l and Western blot techniques. Anticancer Res 12:1965-1972,1992
The above letter was referred to the authms of the article in guestion, who offer the following reply: To the Editor:-We are grateful to Dr Battifora for his interest and thoughtful comments about our article dealing with HER2 (c+erbE-Z/neu)overexpression in human pancreatic carcinomas. We agree that HER2 overexpression in human breast cancers is often defined immunohistochemically by the presence of membrane HER2 immunostaining, which is frequently correlated with amplification of the HER2 gene. We
549