Expert Insights On Diagnosing Pigmented Skin Lesions

By Bradley W. Bakotic, DPM, DO

   During the course of a tightly scheduled office day, a 30-year-old female presents with a painful paronychia involving the lateral border of her right hallux. The painful nail border is acutely inflamed. The doctor temporarily defers a definitive chemical matrixectomy and opts to perform a “slant-back” procedure to remove the offending nail border.

   The doctor adducts the patient’s foot ever so slightly to access the problematic portion of the affected nail unit more easily. While doing so, the clinician notices a tan/brown, slightly elevated papule inferior to the lateral malleolus. The lesion is not particularly large (6 mm) and is of uniform color. However, it exhibits moderate asymmetry of shape. The patient says the lesion had been present her “entire life.” The physician removes the offending nail border and the patient goes home believing that her pedal problems are now resolved.

   This general scenario is not uncommon. The patient may be a 75-year-old man and the skin lesion may be a small scaly plaque, but the net result is often the same: an early evolving malignancy goes undiagnosed. Incidentally, the aforementioned 30-year-old woman was a real patient but, in this instance, the podiatric clinician insisted on performing a biopsy on the atypical lesion. The biopsy disclosed an early evolving melanoma.

Factors That Can Lead To Incorrect Diagnosis

   Readers might question how this could be possible. The patient (a young and competent historian) clearly stated the lesion had been there her entire life. This question leads us to the first important point: some melanomas arise in association with previously benign melanocytic nevi. Clinically atypical lesions must be subject to a histopathologic investigation. I have seen “well-intentioned” and competent clinicians who have been led astray and fell victim to “well-intentioned” and competent historians. This scenario is particularly common when dealing with geriatric patient populations. The simple fact is that melanoma may arise within longstanding, benign pigmented lesions on the skin, the skin of the foot not excluded. The history of longevity should not necessarily preclude obtaining a biopsy if one notes clinical atypia.

   A second point is that cutaneous malignancies are not “rare” in the skin of the foot as many of us were led to believe during our didactic years. Although malignancies related to sun exposure are less common on the foot, they may occur in this location. Melanomas arise in the skin of the lower extremity in 9 percent of cases within the Caucasian population and in half of all cases among African-Americans.1 Overall, as much as 15 percent of all melanoma is of the acral lentiginous type.2 Unfortunately, when melanomas arise on the skin of the foot, they do carry a poor prognosis largely due to delays in diagnosis.3

   If a podiatric physician does not routinely diagnose skin cancer in his or her patient population, it is probably not that he or she hasn’t seen cancer. Rather, it is much more likely due to missed diagnoses. In some cases, we are “bailed out” by other medical professionals who are in a position to make the diagnosis in our stead. However, in many instances, we are not. We must bear in mind that the skin of the foot is foremost the responsibility of the podiatrist and much of the medical community has grown to depend on podiatrists in this regard.

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