Absence of Insulin-Like Growth Factor II Messenger Ribonucleic Acid Binding Protein-3 (IMP3) Immunostain Is Characteristic of Mammary Carcinomas

Document Type

Conference Proceeding

Publication Date

9-2019

Publication Title

Archives of Pathology and Laboratory Medicine

Abstract

Context: IMP3 is a member of the human insulin-like growth factor II mRNA binding protein (IMP) family. Although its expression is readily detected by immunohistochemistry (IHC) in a wide variety of malignant neoplasms, we discovered by serendipity that IMP3 is not detectable in mammary carcinomas. We confirmed this observation by examining IMP3 expression in additional cases. Design: Routinely processed tissues with breast epithelial carcinoma (Table) were examined for IMP3 expression by routine IHC. Sections of paraffin-embedded tissue blocks cut at 4 lm and processed routinely were stained for IMP3 with a mouse monoclonal antibody to IMP3 (Dako Corp) at 1:200 dilution following the vendor’s protocol. The immunostain intensity was graded by both extent and intensity (Table). Viable immature chorionic villi were used as a positive control. Positive stain was defined as .5% tumor cells stained weakly intense (grade 1 of 3). GATA3, a well-established IHC marker of breast epithelium, was also stained for confirmation.Results: Positive immunostain for IMP3 was absent in .95% of invasive ductal and lobular carcinomas, and it was only detected in 1 poorly differentiated tumor examined (Table). All tumors examined stained strongly for GATA3 and were confirmed as being of breast origin by clinical history/follow-up and other IHC studies. Conclusions: Because IMP3 is expressed by a wide variety of carcinomas, the absence of detectable IMP3, together with positive GATA3 immunostain, can be very useful in differentiating mammary carcinomas from other carcinomas in a metastatic setting.

Volume

143

Issue

9

First Page

e150

Comments

College of American Pathologists Annual Meeting, September 21-25, 2019, Orlando, FL

Last Page

e151

DOI

10.5858/arpa.2019-0901-AB

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