Paraffin-embedded Tissue Fragment Suspension (PETFS): A Novel Method for Quality Control Preparation in Immunohistochemistry

Immunohistochemistry (IHC) is one of the most important adjunctive techniques in surgical pathology. Quality controls are essential for staining interpretation. The most common controls are cut from the formalin-fixed, paraffin-embedded tissue blocks in advance. In contrast, we developed paraffin-embedded tissue fragment suspension (PETFS), a novel method in liquid form, for quality control preparation. The liquid form controls were cut from the donor formalin-fixed, paraffin-embedded paraffin blocks, stored in the 4°C fridge easily, and added to the top and bottom of the test slide directly by pipetting. The tissue fragments from the PETFS had a comparable IHC staining pattern to that of the control sections from the original donor blocks. Over a 180-day testing period, the IHC staining pattern and intensity remained strong and specific. The clinical value of PETFS method was further validated by their successful application as controls for the expression of estrogen receptor, progesterone receptor, and C-erbB-2 in 240 breast invasive ductal carcinomas. We concluded that PETFS is a fast, low-cost, and less donor tissue consumption robust technique as quality controls for routine IHC staining in surgical pathologic practice.