Cath Lab Digest

General guidelines for obtaining biopsies of skin lesions are few and far between. These techniques are also often underutilized in podiatric practice. Accordingly, this author offers a helpful primer on when and how to perform punch, incisional and excisional biopsies.

   Why does a physician perform a skin biopsy? Often skin neoplasms and inflammatory conditions look alike and are clinically confusing. In these cases, a biopsy can facilitate a histopathologic diagnosis, which helps to support the treatment plan.¹

   Obtaining a skin biopsy can also help to clarify the skin disorder when a treatment plan is not yielding the appropriate results. For example, perhaps a topical antifungal is not yielding effective results in treating the inflammatory disorder.

   Lastly, a biopsy can be curative or even lifesaving if one excises the lesion in toto or when the biopsy helps identify a treatable malignant diagnosis. Ultimately, a biopsy can both complement and confirm the diagnosis.²

   In order to have the best biopsy result, physicians must ensure all three layers of skin (epidermis, dermis and subcutaneous tissue) are present.

   A “scraping” of the skin, in which one sends the scales of the lesion to pathology, is not appropriate to diagnose any inflammatory skin disorder or neoplasm. Physicians should only use this “scraping” technique when doing a potassium hydroxide (KOH) test to determine the presence of a dermatophyte.

   Podiatrists should also avoid superficial shave biopsies as they do not involve the deep dermis or subcutaneous tissue, which is needed for many histopathologic diagnoses and staging of the neoplastic disease.

   Both the “scrape” and superficial shave ultimately delay a true diagnosis and create a lot of frustration for the patient. Additionally, physicians should never perform the scrape and superficial shave if they suspect a malignant lesion.

   When it comes to biopsies in the podiatric physician’s office, one should be familiar with the punch biopsy, the incisional biopsy and the excisional biopsy.

   In addition to performing the appropriate procedure, giving the pathologist sufficient clinical information is important in order to receive a helpful diagnosis.³ When you are filling out the pathology form, provide sufficient detail on the evolution of the lesion or dermatitis, the clinical description, the specific anatomic location of the biopsy site, and the differential diagnosis.

   What should the podiatric physician biopsy? Ideally, you should biopsy any inflammatory lower extremity disorder with a questionable diagnosis, any blistering “rash” and any suspicious neoplasm.²

   Podiatrists should always obtain consent and forewarn the patient about the possible need for further surgery. For example, a second excision may be necessary for an atypical or malignant lesion. One should also counsel the patient about the possibility of a painful scar, especially when the lesion in question involves the plantar foot.

   To reiterate, the location of biopsy and use of the proper fixative medium are also imperative for optimum results.

   What should one avoid? When it comes to sites of active infection, physicians should not biopsy these unless they need more information about them (i.e. cutaneous larva migrans). One should also refrain from biopsies for areas that are excoriated or crusted, or when there are older stages of dermatitis as a biopsy in these clinical scenarios will give a vague diagnosis.