Treating A Pigmented, Slightly Pruritic Nodule

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Key Questions to Consider

1. What essential question does one still need to ask to help make the diagnosis?

2. What is the tentative diagnosis?

3. Can you list at least three differential diagnoses?

4. In regard to the differential diagnosis, what features of this condition differentiate it from other conditions?

5. What is the suitable treatment of this condition?

Answering The Key Diagnostic Questions

1. Do you recall any previous injury, insect bite or other problems in the area of the lesion?

2. The most likely diagnosis is a solitary dermatofibroma
(fibrohistiocytoma).

3. The differential diagnosis includes but is not limited to epidermal cyst, keloid scar, prurigo nodularis, basal cell carcinoma, dermatofibrosarcoma protuberans, foreign body granuloma and insect bites and stings.

4. The condition is characterized by skin lesions that are papular or nodular, firm, raised, round-to-oval and pigmented. They usually retract beneath the skin surface when one squeezes them from either side. This is called the Fitzpatrick Dimple Sign.

5. Treatment is usually not necessary but when these lesions are symptomatic or problematic, one needs to remove them surgically. However, since they are deep, this usually leaves a visible hyperpigmented scar. Cryotherapy may eliminate much of the color of the lesion. It may also flatten and reduce the size of the lesion. Cortisone injections using 4 mg/mL of dexamethasone sodium phosphate may also be helpful.

34
Author(s): 
By G.“Dock” Dockery, DPM, FACFAS

A 37-year-old Caucasian male presents with a chief complaint of a nodular growth on the left calf. He first noticed the bump about two months ago but says he did not think too much about it until recently. At that time, he noticed it was causing mild discomfort when he touched it but the growth was only slightly pruritic. The lesion did not appear to be infected and it did not drain or bleed at any time. He says he checked the rest of his body for any similar looking lesions and found none. Otherwise, he has no other complaints or concerns.

The patient has not changed his diet or eating habits, and has been healthy for the past year. He denies any out-of-state or foreign travel, and has not changed his occupation or hobby activities in several years. The patient reports no known exposures to any new chemicals, paints, toxins, irritants or other potential allergens. He denies taking any medications, vitamins or supplements. No one else in his household or within his family has any similar conditions. He has never had similar signs or symptoms in the past that he can recall.

What The Exam Revealed

Upon examination, the patient demonstrates a pigmented nodular lesion on the anterior lateral calf that is 0.8 cm in size and dome shaped. It is reddish-brown with a smooth surface and a slightly hyperpigmented ring around the base of the lesion. A careful cutaneous examination shows no similar lesions or any other distinctive skin lesions elsewhere on the torso, arms or legs. There are also no color changes or inflammation involving the hands or feet. The fingernails and toenails are normal in appearance.

The patient’s vital signs and pedal pulses are normal. The remaining portion of the physical examination is within normal limits and the patient has no other clinically significant skin conditions.

A Closer Look At Dermatofibromas

The most likely diagnosis is dermatofibroma (fibrohistiocytoma), which is a common cutaneous nodule of unknown etiology that occurs more often in women with a female-to-male ratio of 4:1. The condition frequently develops on the lower legs (80 percent of cases) but may arise on any body region. These nodules are usually asymptomatic although pruritus and tenderness are common findings. Women who shave their legs may be troubled by the razor cutting the lesion in that region as it may lead to increased pain, bleeding, erosive changes and ulceration.

These nodules are considered to be the most common of all painful benign skin tumors. Although they may occur at any age, dermatofibromas most frequently affect individuals in early to middle adult life with about 20 percent of lesions occurring before the age of 17. They are usually solitary in nature but clinicians may see multiple lesions. The multiple variant (15 or more lesions) is most frequent in the setting of autoimmune disease or altered immunity (i.e. systemic lupus erythematosus, HIV infection or leukemia).

Typically, the clinical appearance of the lesion is a solitary, 0.5- to 1-cm nodule. They may enlarge up to 2 cm in some cases. Giant dermatofibromas (> 2 cm) and atrophic variants have been reported. The overlying skin of the characteristic lesion of the dermatofibroma may range in color from flesh to gray, yellow, orange, pink, red, purple, blue, brown or black. Upon palpation, the dense nodule may feel like a small stone or frozen pea attached to the skin surface, which is freely movable over the subcutaneous layer. Tenderness is common with movement of the lesion or with direct pressure. Roughly 80 percent of all dermatofibromas will involute or withdraw below the surface of the skin when one applies lateral squeeze compression, creating a dimple in the skin. Although this “dimple sign” is not exclusive to dermatofibromas, it is still a very useful clinical sign.

In the past, many experts attributed dermatofibromas to some external injury such as a small cut, a penetrating foreign body or insect bite but the true cause is still undetermined. More recent articles suggest that dermatofibromas are more likely to be a neoplastic process as opposed to a reactive tissue change because of the persistent nature of the lesion.

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