Skin tumour specimen shrinkage with excision and formalin fixation-how much and why: a prospective study and discussion of the literature.

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Surgical skin specimens are known to undergo significant shrinkage when excised and processed. The degree of shrinkage is important for medical care, research and third-party assessment. Studies to date have shown variable degrees of shrinkage. Most have included multiple and sometimes unspecified variables-different surgeons, varied sites, ill-defined excision patterns and/or multiple pathologies. This study tries to exclude many of these variables to try to ascertain a more accurate predictor of shrinkage with a single surgeon, lower limb only site using a controlled excision pattern and restricted pathology cohort. 100 previously untreated malignant BCC's and SCC's on the lower limb were excised and measurements made of the resulting wound and the specimen removed. Measurements were subsequently made after pathologic processing and statistically compared. With excision of lower limb skin tumours the surgical defect enlarges significantly (15%) and the specimen shrinks significantly (20%) in both length (12%) and width (9%). The specimen shrinks a further 11%-again shrinking in length (8%) and width (2.6%) with formalin processing. The pathology specimen is 28.6% smaller than the specimen marked for excision. Anatomical site contributes to the degree of shrinkage. The pathologic specimen is only 75% of the suture repaired wound length. Skin specimens shrink significantly both with excision and processing. Most shrinkage (70%) takes place with excision while the remaining 30% with processing. The shrinkage takes place disproportionately in the normal tissue component of the specimen. Age, anatomical location, and pathology appear to play a part.