Which Biopsy Method is the Best for Pigmented Lesions?
By Darrel Arthurs, ARNP, DCNP
A literature review was conducted to determine, "What is the best biopsy method for pathology diagnosis of malignant melanoma?"
There are three types of biopsies that can be performed in the office, which will aid in the diagnosis of melanoma. First, a wide local excisional biopsy is where an ellipse of skin is removed with the entire pigmented lesion intact. Second is a punch biopsy where a small circular piece of tissue is removed to the fatty layer. Finally a shave biopsy where a saucerization is performed around the lesion, within the dermis, and an attempt to obtain as much of the lesion as possible is performed.
The National Comprehensive Cancer Network guidelines recommend excisional biopsy as the preferred method. However, there may be a variety of reasons this type of biopsy cannot be performed. One of the most recognized reasons is clinician's level of expertise. For instance, some lesions may just be too large to remove safely depending on the skill level of the provider. Other lesions may be in an anatomically impractical location such as on the ear, face, or feet. For these reasons some providers may not be comfortable doing an excisional biopsy. Therefore, an alternative method is needed but which one is the best choice?
There are many concerns about doing either a punch or shave biopsy in place of performing an excision. If the entire depth of the lesion is not obtained it will be difficult if not impossible to measure the Breslows depth, which is used to grade the tumor stage. Without this information the treatment course may be more of a guess as opposed to using strong clinical guidelines based on studies and patient outcomes. A shave biopsy is concerning for not getting the entire depth of the lesion. Proper training can significantly improve the outcome of the shave biopsy and increase its clinical value however occasionally the base of the lesion is still missed. A punch biopsy will only obtain a portion of the pigmented lesion however, it does take a full thickness of the skin. The obvious drawback to this biopsy is that it will only take a small area of the lesion. It was found that punch biopsies were best used in smaller lesions less than 1 cm diameter and that the punch used was nearly as large if not larger than the lesion itself.
Not surprisingly the findings concluded that both procedures resulted in more residual disease than wide local excisional biopsy. Punch biopsies were associated with even more residual disease than shave biopsies were. It was also found that both biopsies were frequently associated with upgrading in tumor severity on subsequent pathology in comparison to original biopsy. This was particularly true for the punch biopsy which frequently only takes a small portion of the lesion present. The shave biopsy was the least upgraded of the two methods however it was still, often times, upgraded as well. It was also found that training levels of the clinicians greatly impacted the upgrading of both biopsies.
Overall, the findings indicated that biopsy type did not impact the diagnosis of malignant melanoma. It also did not adversely impact the outcomes
of any diagnosed melanoma. The most important factor was getting the diagnosis of melanoma quickly and then referring the patient for the appropriate intervention. If a melanoma is suspected a biopsy needs to be done immediately. It is most preferable that biopsies of these lesions be completed at the time of initial findings and not at a later date. A provider may not be able to perform a wide local excisional biopsy immediately but either a shave or a punch biopsy can be safely used to diagnosis malignant melanoma as well. If these biopsies are used in the correct situations and appropriate follow-up with a surgeon is adhered to the outcomes for the patients can be truly positive.
Arthurs' passion for dermatology developed while he was serving in active duty in the U.S. Navy. Since then he has accumulated over 11 years' experience in medical and surgical dermatology. Currently he works independently in a small city in northeastern Oklahoma. Arthurs' is on the NADNP Board of Directors