When Should You Biopsy?
When performing a biopsy for a suspected basal cell carcinoma or squamous cell carcinoma, one may perform a deep punch or incisional biopsy of the base and the wound edge.3 For pyoderma gangrenosum, two biopsies (punch or incisional) that include the wound edge (with partial ulcer bed) and the central base will be useful. When an ulcer is associated with vasculitis, the center of the lesion is best to biopsy but a punch of newly formed palpable purpura would also be diagnostic. One should send a specimen for direct immunofluorescence staining in a special media (Michel’s fixative) and the pathology lab of choice can assist the clinician in obtaining a kit for easy transport. Otherwise, one should send all other specimens for histopathology in 10% formalin solution.
Overall, one should obtain a sample of a wound that has not decreased in size after several months of standard care, has changed in a negative manner, has a suspected etiology beyond the original diagnosis and has a potential for being malignant. Send this sample for a histopathologic review.
When Rashes Do Not Seem To Respond To Treatment
All of us have experienced a patient whose red, scaly rash has not responded to our prescription topical therapy. Not only is this challenging to us as practitioners but also to the patient. Failure to respond to conventional therapy warrants a skin biopsy.
In these cases, a punch biopsy is an appropriate choice. I have also utilized this procedure in patients who have seen numerous practitioners prior to a visit with me, have a long list of failed medications and have not had a skin biopsy to define the skin condition. In these cases, I choose to perform the skin biopsy prior to initiating any further treatment in order to refine my management plan and reduce the patient’s frustration of purchasing yet another possible failed therapy.
I do not recommend routine biopsy of all skin rashes. However, if a new onset rash does not correspond to the conventional presentations of psoriasis, eczema and lichen planus, a punch biopsy can be a useful diagnostic tool (see the table “A Closer Look At Biopsy Recommendations For Inflammatory Skin Conditions” above at right). In the case of a psoriatic-like plaque, differential diagnoses can range from plaque psoriasis to cutaneous T-cell lymphoma. Treatment plans for these two diagnoses vary in approach and prognosis.
When To Biopsy Suspicious Pigmented Lesions
Over the course of a career, the podiatric practitioner will face diagnosing benign lesions (nevi, dermatofibroma), pre-cancerous lesions (actinic keratosis), non-melanoma skin cancer (basal cell and squamous cell) and melanoma (see the table “A Guide To Biopsies For Pigmented Lesions” below at right).
When facing a pigmented lesion, it is important first to establish if the lesion is melanocytic. Examples of melanocytic lesions are nevi, lentigines, atypical nevi and melanoma. Early detection of a melanoma is ideal but choosing which melanocytic lesion to biopsy can be difficult. A biopsy of every pigmented lesion on a patient would be “disfiguring and unnecessary.”4 The combination of clinical examination and choosing the appropriate biopsy type for the lesion can aid in diagnosis and management.
After performing a thorough history and physical exam, and prior to the biopsy, one may consider adding dermoscopy and confocal microscopy to the exam when trying to determine if and where to biopsy. Dermoscopy requires special instrumentation and education, but it is a valuable technique in refining the decision of whether or not to biopsy. As with any technique, there are limitations and the dermoscopy exam can yield questionable and vague results.