Utility of Immunocytochemistry on Direct Smear Preparations in the Diagnosis of Effusions
Stewart M Knoepp, Jeremiah Placido, Kristina Fields, Dafydd Thomas, Michael H Roh. University of Michigan Medical School, Ann Arbor, MI
Background: Metastatic malignancy represents a common cause of effusions. Immunocytochemistry (ICC) is useful in confirming a diagnosis of malignancy and gaining insights into sites of origin. Cell blocks are commonly utilized for this purpose; nonetheless, it is not uncommon for the malignant cells to present as a minority population within the milieu of background mesothelial cells and histiocytes. In cases where the malignant cells are sparse, they may not be represented in cell blocks thereby precluding immunophenotypic characterization. Thus, we sought to investigate the utility of direct smear preparations as a platform for ICC in the diagnosis of effusions.
Design: Air-dried, unstained direct smears were prepared for 48 malignant effusions and 17 reactive effusions for comparison. ICC for the following markers was performed following brief formalin fixation and antigen retrieval: EMA, MOC-31, p63, TTF-1, Napsin-A, PAX8, CDX-2, and calretinin.
Results: The results of ICC for the malignant effusions are summarized in the table below.
|Malignancy (# cases)||Immunostain||# Positive (%)|
|Mullerian ADC (n=15)||EMA||15 (100%)|
|Lung ADC (n=9)||EMA||9 (100%)|
|Pancreatic ADC (n=5)||EMA||3 (60%)|
|Gastric ADC (n=4)||EMA||3 (75%)|
|Breast ADC (n=4)||EMA||4 (100%)|
|Urothelial carcinoma (n=4)||p63||3 (75%)|
|Mesothelioma (n=2)||EMA||2 (100%)|
|Colorectal ADC (n=2)||EMA||1 (50%)|
|Lung squamous cell carcinoma (n=1)||p63||1 (100%)|
|Papillary thyroid carcinoma (n=1)||EMA||1 (100%)|
|Anaplastic thyroid carcinoma (n=1)||EMA||1 (100%)|