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Joe R. Monroe, PA-C, MPAS, DEPARTMENT EDITOR
A condition that is more than skin deep
Joe R. Monroe, PA-C, MPAS
The author practices at The Dermatology Clinic, Oklahoma City, Okla, and is the founder and President of the Society of Dermatology Physician Assistants. He has indicated no relationships to disclose relating to the content of this article.
The primary care provider for an 81-year-old man recently referred him to the dermatology department for evaluation of a leg rash. The lesions, which were minimally symptomatic, had been present for several weeks but had been growing in size and number despite treatment with antifungal and topical corticosteroid creams. The patient had even been on a month-long course of terbinafine, 100 mg daily, which also had had no effect. He denied having had a condition like this before and further denied scratching or rubbing the lesions. The patient was taking a number of medications but was not immunosuppressed. He had no history of cancer, though he had had a recent unexplained 10-lb weight loss. He had never lived in or visited the desert Southwest.
 Examination showed three plaques on the anterior tibial area of the left leg, the largest of which had significant scaling on its surface and measured approximately 8 cm at its largest dimension (see Figure 1). The lesions—especially the large one—had two striking features: the color was purplish brown with translucent margins, and the lesions were rock hard instead of soft, as is usually seen in common conditions. Potassium hydroxide (KOH) examination of the scale revealed no fungal elements. Examination elsewhere showed no other significant abnormalities of the skin. Punch biopsies (4-mm) of all the lesions were performed.
Given these facts, the most likely diagnosis is
- Psoriasis vulgaris
- Deep fungal infection
- “Skin” cancer
- Neurodermatitis
Discussion
The correct answer is “skin” cancer. The biopsy results revealed that the lesions were metastases from colon cancer, but they could well have originated from any number of other primary lesions. Psoriasis vulgaris is incorrect. The depth and firmness of the lesions, the lack of corroborating involvement elsewhere, and the biopsy findings ruled out that diagnosis.
These lesions could conceivably have represented a deep fungal infection, but certainly not a superficial one given the marked induration. Deep fungal infections are quite unusual, however, and the patient seemed far too well to put these at the head of our list of suspects.
Neurodermatitis, also known as lichen simplex chronicus, would also be an incorrect diagnosis. This condition involves highly pruritic skin, which thickens, sometimes markedly, and may even become lesional with chronic, prolonged scratching and/or rubbing. This patient’s lesions were remarkably asymptomatic; thus there was no reason to suspect that scratching or rubbing played a role in his condition. When a lesion falls outside the parameters of what common conditions would look like, one must consider alternatives. Biopsy is at the heart of that process. An equally important point is that skin cancer is not always a basal or squamous cell cancer or melanoma. It can represent lymphoma, leukemia, or a metastatic cancer from a wide variety of sources. These kinds of cases, especially in an older patient, are far from rare.
As of this writing, this patient was still in the process of being evaluated for his primary cancer. Obviously, his prognosis is guarded at best. If his skin lesions get larger, local radiation therapy will control them.
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