A Biopsy Is More Than a Biopsy

This issue of JGIM contains a review, by Alguire, about commonly performed skin-biopsy procedures that serves as a comprehensive reference for generalists.¹ Generalists need to know more than biopsy technique, however, especially now that managed care is pressuring them to do more themselves and to refer less to consultants like dermatologists.

Six to 22 percent of visits to generalists involve dermatologic care.² With the recent growth and influence of managed care, generalists, serving as the “gatekeepers,” will undoubtedly continue to see more patients with skin disease. For patients in health maintenance organizations and with other forms of prepaid insurance, there were increases in the proportion and rate of dermatologic visits between 1988 and 1992 when internists were compared with dermatologists.³ Generalists stand at the forefront of diagnosing patients with skin disease, as evidenced by the fact that primary care providers discover 25% of melanomas.⁴ Furthermore, the number of visits related to malignant skin tumors is greater for nondermatologists than for dermatologists.⁵ Therefore, generalists, who are now experiencing pressure to provide more comprehensive medical care, should consider learning more than the technique of skin biopsy—they should become educated in skin disease.

Such an education provides the physician with both an awareness of and the ability to treat the potential complications of a skin biopsy. These complications include differences in healing based on anatomic location and comorbid disease and the risks of infection at the biopsy site, allergic contact dermatitis to adhesives or topical antibiotics, wound dehiscence, and anesthetic complications from epinephrine. Also included would be the consideration for antibiotic prophylaxis in selected patients with cardiac murmurs and prosthetic valves.

Becoming educated in skin disease also means learning the more difficult aspects of the biopsy which are the differential diagnosis, the selection of the appropriate biopsy technique for a given lesion, and the interpretation of the histologic findings.

A differential diagnosis provides the reason for performing a skin biopsy, much as auscultation of a murmur leads to an echocardiogram. The differential diagnosis also determines the type of biopsy to perform. For example, a pigmented lesion with melanoma in the differential diagnosis should have a biopsy that is representative of the entire lesion, and thus total primary excision always is recommended. When total excision is not feasible, however, a biopsy should be performed through the darkest and thickest area. A deep biopsy is critical because tumor thickness is the single most important criterion in predicting survival for patients with stage I melanoma.⁶ The superficial nature of the shave biopsy potentially does not sample the deeper portion of the melanoma, thereby eliminating the possibility of accurate prognosis. As an exception, a deep shave biopsy may be permissible for a lesion indicative of lentigo maligna, which is an in situ melanoma. A punch biopsy may lead to sampling error, especially when sampling lentigo maligna.⁷ Therefore, the clinician must know the clinical and pathologic aspects of melanoma before performing a biopsy of a suspected melanoma.

Interpretation of histologic findings as described in the biopsy report can be straightforward or difficult. For example, a biopsy of a neoplastic lesion, such as basal cell carcinoma, is usually straightforward. If the biopsy report is basal cell carcinoma, referral can be made for surgical removal. On the other hand, a biopsy of a pruritic, scaly eruption is often nondiagnostic. The biopsy report might be “chronic inflammation with spongiosis,” which may be seen with a variety of diseases, including atopic dermatitis, drug hypersensitivity reaction, irritant contact dermatitis, or pityriasis rosea. Clinical correlation is necessary to determine a working diagnosis and then to determine appropriate management.

In addition, the clinician should be familiar with the pathologist who interprets the biopsy specimen. Most dermatologists learn the dermatopathologist's diagnostic boun-daries, for example, how an actinic keratosis is differentiated from a squamous cell carcinoma. Unfortunately, in this era of managed care, skin biopsy specimens are often sent to general pathologists who lack specialized training in skin biopsy interpretation and clinical dermatology compared to dermatopathologists. With the relationship between the clinician and the pathologist less established, potential exists for decrease in quality of care. One study showed that 7.1% of 364 skin biopsy specimens sent to anonymous consultants in managed care organizations were diagnosed incorrectly. In two instances, malignant neoplasms were reported as benign.⁸

Even generalists who want to become educated in skin disease may not find it easy. A survey of residency program directors in internal medicine found that less than 20% thought that residents mastered the technique of performing a skin biopsy.⁹ Furthermore, there are no credentialing requirements. Training of medical residents in general dermatology can range from none to 4 weeks.¹⁰ It is not surprising then that internists and internal medicine residents perform poorly in the diagnosis of common skin diseases.¹¹ What is especially concerning is that primary care residents failed 50% of the time to diagnose nonmelanoma skin cancer and malignant melanoma correctly.¹² One study showed that more than half of the biopsies thought necessary by both internal medicine attending physicians and residents were unnecessary, which raises additional issues about cost.¹³

To improve opportunities for dermatology education, dermatologists should work with generalists to establish a curriculum starting in medical school and extending into residency training.¹⁴ Recognizing this need, the American Academy of Dermatology is currently developing a core curriculum for medical schools that covers basic science and clinical dermatology (Jean Bolognia, MD, personal communication).

Dermatologic education also can take the form of photographs (The National Library of Dermatology Teaching Slides, American Academy of Dermatology, T847-330-0230), computer-assisted learning (http://tray.dermatology.uiowa.edu/home.html), and preceptorships. Evidence suggests that, with repeated exposure, generalists can improve their detection of harmful lesions.¹² These skills then need to be maintained through continuing education with quality assurance monitoring.

Are generalists being prepared to assume the role of gatekeeper when managing skin disease? Learning the technique of a biopsy is just the start.—Jeffrey J. Miller, MD,Department of Dermatology, University of Pennsylvania Health System, Philadelphia.