Painting the surgical margins of a tumor biopsy
A common problem faced by pathologists is interpreting surgical margins of tumor biopsies. Although it is often easy to distinguish surgical margins from those produced during the trimming process in the histology laboratory, it is sometimes difficult and frustrating for both pathologists and clinicians. Diagnosticians know that the three most common questions posed by the clinician regarding a neoplastic process are "What kind of tumor is it?", "Is it benign or malignant?" and "Are the margins free of neoplastic cells?"
In human medicine, surgical margins of a biopsy are commonly painted with a dye that adheres to tissue and is visible under the microscope. This procedure is simple and does not interfere with histologic evaluation. Its advantage is that it clearly distinguishes surgical margins from trimming margins. This is essential to assess complete/incomplete excision of a tumor.
Biopsy margin painting can be done on unfixed or fixed tissues; however, painting unfixed tissues is easier and preferred. There are several commercially available products for this purpose (call the ADDL for additional information if needed). The use of different colors (black, blue, green, red, yellow, etc) for different aspects of mass orientation is superior to using sutures of different colors. Painting biopsy margins is also inexpensive; a 20 ml bottle of dye will last several years. ADDL staff can paint fixed specimens, but an additional fee with accrue.
How to do it: You don't have to be a Picasso!
1) Blot the biopsy margins of the mass.
2) Select the dye color.
3) With a wooden applicator stick or cotton swab, "paint" the biopsy margin.
Do not pour dye on the surface; just apply as if painting.
4) Let the dye dry for 5-10 minutes and immerse the sample in regular fixative solution. Some of the dye will dissolve with the fixative; that's OK. If the sample is thicker than 4-6 mm, section it to improve penetration of fixative as you usually do.
In summary, you will get more from your biopsy report if you mark biopsy margins with dye.
Legends to Figures.
Painting the margins of the biopsy with black ink. A wooden stick or cotton swab can be used. Be sure to blot the surface before painting.
Other colors can be used (black and red depicted).
This biopsy of skin was painted with five different colors.
Using different colors can identify specific biopsy margins.
Once the margins are painted, air-dry the sample for 5-10 minutes and place it in formalin. Some dye will leach into the fixative.
Note that the dyes remain on the surgical margin in this cross-section of the biopsy with minimal infiltration of adjacent tissue.
Microscopic appearance of the margins of a lipoma painted with different dyes; (a) black, (b) red, (c) yellow, (d) blue.