Determination of formalin fixed tissue diminution after processing and its significance in surgical margins and tnm staging: a prospective review of 42 cases in a tertiary health center

Introduction: Tissues shrink after fixation and post processing before final microscopic assessment by the pathologist. Many studies indicating shrinkage of tissue post-fixation with possible corrective factors have been highlighted in many studies, however, it is imperative to determine shrinkage during tissue processing which forms a critical position in determining surgical margins and in tumour staging using TNM classification, it is the paucity of information regarding that prompted the need for this study.
Methodology: Forty-two tissue biopsies were randomly selected prospectively during surgical cut off and specific block is selected and their volumes were measured using meter rule post-fixation, after automated tissue processing. The tagged block diameter (volume) was then retaken, the percentage shrinkage was then determined. Correlation of shrinkage with age, sex, site of the biopsy and diagnosis was analyzed using SPSS version 16 and presented in simple tables and bar charts.
Results: Forty-two cases were selected during grossing. There were 10 malignant neoplasms, five cases were benign neoplasm, eight were inflammatory lesions and 19 cases are nonneoplastic lesions. The age ranges were between 2 to 85 years with mean age of 38.5. There were 25 females and 17 males. The peak % shrinkage was observed in malignant neoplasm and inflammatory lesions with mean % shrinkage of 43.7 and 61.3 respectively. Overall least shrinkage was seen in non-neoplastic lesions. The benign neoplastic lesions show fairly uniform shrinkage ranging between 46 to 64%. Tissue shrinkage also depends on nature of specimens, site of biopsy, the age of the patient and type of lesion.
Conclusion: Shrinkage of tissue post processing is very significant finding that can give rise to false surgical margins and TNM stage with the resultant impact on prognostication of tumour. There is a need to develop shrinkage corrective factors for each type of malignant neoplasm and that has to be center based depending on the method of tissue processing and processing machine in order to resolve surgical margin incongruities and staging.