Post-Excision Shrinkage of Feline Skin Tissue Specimens
Sara A. Colopy, DVM, PhD, DACVS, University of Wisconsin–Madison
In the Literature
Risselada M, Mathews KG, Griffith E. Effect of feline skin specimen preparation on postexcision and postfixation tissue shrinkage. J Feline Med Surg. 2016;18(12):970-975.
The Research …
One of the main goals of surgically treating skin tumors is achieving tumor-free margins. Tumor margins obtained determine whether adjunctive therapies (eg, radiation treatment) are recommended after surgery. It has been documented in humans and dogs that skin tissue samples shrink significantly after excision.1-3 This could lead to underestimation of the actual tumor-free tissue margin obtained in surgery and overrecommendation of adjunctive therapies.
Figure 1A
Surgical images from a dog with a 1-cm mast cell tumor in the left inguinal region. Margins of 2 cm are drawn around the mass. The total planned area to removed measures 5 cm in diameter.
This study examined skin–muscle–fascia specimen shrinkage in skin samples obtained from feline cadavers. Gelatin spheres (representing the tumor) were implanted in paired thoracic subcutaneous pockets and excised with 30-mm lateral margins and a fascial plane deep to the “tumor.” Excised skin and underlying fascia were either left unsutured or the skin was sutured to the fascia in either a 4-quadrant–sutured or circumferentially sutured pattern to prevent tissue translation. The lateral margins were measured on the excised and formalin-fixed specimens. The donor site defect was measured for enlargement after specimen excision.
The mean closest margin decreased by 42.4% after excision and by 58.7% after formalin fixation as compared with the originally measured gross tissue margin. The change in size of the lateral margins was not altered by suturing the excised skin to the fascia.
The donor site fascial and skin defects were significantly larger than originally planned.
… The Takeaways
Key pearls to put into practice:
Surgical planning for skin tumors is based on palpable gross tissue margins in surgery. A minimum margin of 2-3 cm around the perceived borders of a malignant tumor and a single fascial plane below is typically recommended.
Surgeons should prepare the tissue sample for histopathologic analysis and provide as much information as possible to the pathologist. Suturing tissue layers together (skin-to-fascial layers in this case) in either an interrupted or continuous fashion prevents tissue translation during processing without compromising assessment of lateral margins. Surgical samples should be inked by the surgeon with official surgical ink to orient samples, visibly identify all surgical margins (lateral and deep), and denote areas of greatest concern.
Skin specimen shrinkage after excision may result in reported surgical margins that seem significantly smaller than what was measured at the time of surgery. The decision to pursue additional adjunctive local therapy (eg, revision surgery or radiation) should be made carefully, based on knowledge of the gross tumor anatomy and biological behavior. Contacting the pathologist directly when there is confusion regarding surgical margins is recommended.