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Updated: Apr 1, 2026
Author Spotlight: Efficient Detection of Immune Cell-Infiltration in Cancer Tissues Using Fluorescent Immunohistochemistry
Published on: January 26, 2024
Practical Applications in Immunohistochemistry: Carcinomas of Unknown Primary Site
Patricia L Kandalaft1, Allen M Gown1
1Department of Immunohistochemistry and Anatomic Services, Pacific Pathology Partners, Seattle, Washington (Dr Kandalaft); PhenoPath Laboratories, Seattle (Dr Gown); and Department of Pathology, University of British Columbia, Vancouver, British Columbia, Canada (Dr Gown).
Context:
-Identification of the site of origin of carcinoma of unknown primary using immunohistochemistry is a frequent requirement of anatomic pathologists. Diagnostic accuracy is crucial, particularly in the current era of targeted therapies and smaller sample sizes.
Objectives:
-To provide practical guidance and suggestions for classifying carcinoma of unknown primary using both proven and new antibodies, as well as targeting panels based on integration of morphologic and clinical features.
Data Sources:
-Literature review, the authors' practice experience, and authors' research.
Conclusions:
-With well-performed and interpreted immunohistochemistry panels, anatomic pathologists can successfully identify the site of origin of carcinoma of unknown primary. It is crucial to understand not only the diagnostic uses of the many available antibodies but also the potential limits and pitfalls.
