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.
Most dermatofibromas remain unchanged for many years or even continue indefinitely. There are infrequent reports of spontaneous regression of dermatofibromas. When this occurs, it may yield a postinflammatory hypopigmentation response. There are rare reports of the uncommon occurrence of dermatofibromas and melanocytic lesions (melanomas) arising in the same biopsy specimen.
A Guide To The Differential Diagnosis
Epidermal cyst. The common epidermal inclusion cyst occurs secondary to trauma with implanted epidermis within the dermis. The cysts may have a thin epidermal cover with small blood vessels visible in the dome or they may have a very thick epidermal cover with overlying hyperkeratotic tissue. Lateral squeezing causes the lesion to enlarge and bulge outward. This lesion grows slowly and may spontaneously drain.
Keloid scar. Keloid scars typically proliferate and extend into normal surrounding skin. The borders are distinct but irregular or bizarre in outline. In some cases, the scar may appear as a hyperpigmented nodular lesion. Keloid scars are very resistant to all forms of treatment, especially surgical excision.
Solitary prurigo nodularis. Solitary prurigo nodularis is an uncommon lesion that presents as extremely pruritic nodules with the most common location on the extensor aspects of the extremities. They are caused by chronic, repetitive picking and rubbing. In generalized prurigo nodularis, there are multiple nodules. Lesions tend to be symmetrical and are associated with excoriations due to the intense pruritus that is present. Many authorities believe this to be a variant of lichen simplex chronicus or a nodular form of neurodermatitis circumscripta.
Basal cell carcinoma. The most common form of basal cell carcinoma, the nodular form, begins as a small, white, dome-shaped nodule or papule. As it expands, telangiectatic vessels become more prominent and the tumor may appear erythematous. The center of the lesion may ulcerate and bleed, and then it never seems to heal. As with other forms of carcinoma, basal cell carcinoma may mimic many other forms of skin lesions.
Dermatofibrosarcoma protuberans. This lesion is a relatively uncommon soft tissue neoplasm with intermediate to low grade malignancy and is a very slow growing tumor. Due to the slow progression and rarity of this condition, the diagnosis is often delayed. It may start as a small asymptomatic papule, which is likely ignored. The tumor may gradually enlarge into a lumpy nodule or it may evolve into an atrophic and/or sclerotic plaque. When encountering an atypical scar-like lesion, the clinician should consider a skin biopsy.
Foreign body granuloma. A benign foreign body granuloma is characterized by a simple macrophage reaction to a penetrating foreign body into the dermis. Normally, the foreign body cannot be broken down or rejected, and is eventually surrounded by foreign body giant cells and walled off. This creates a solid granuloma that is difficult to differentiate from scar and dermatofibroma.
Insect bites and stings. These may involve any area of the body but are common on the arms and legs. Most bites are on the dorsum of the hand and foot rather than the palmoplantar surfaces. The resultant lesion may appear to be raised or nodular. In most cases, the reactions from bites are much more erythematous and inflamed than one would find with a dermatofibroma.
Other painful tumors. One may remember painful tumors of the skin by using the mnemonic: LEND AN EGG for leiomyoma, eccrine spiradenoma, neuroma, dermatofibroma, angiolipoma, neurilemmoma, endometrioma, glomus tumor and granular cell tumor.
Key Insights On The Treatment Of Dermatofibromas
No treatment is necessary for most dermatofibromas. However, most patients tend to want something done to remove them. For lesions that are cosmetically undesirable or those that are symptomatic, or have changed clinical appearances in any way, there are treatment options.
Injections with intralesional corticosteroids may decrease the size and color of lesions. In many cases, the steroid will make them softer. Steroid injections are not considered to be highly successful and have some potential complications of atrophy, discoloration and/or telangiectasia. Some physicians have stopped recommending this approach. Cryosurgery is also useful in flattening and decreasing the color of lesions. This approach does not have the potential side effects of steroid injections.
Since dermatofibromas are deep lesions with widened bases, simple excision of the lesion may result in unsightly, thick and dark scars. Recurrences are common. Wide excision of the lesion and complete removal of the deep portions of the mass are necessary to prevent return of the lesion. One may subsequently close the resultant defect with a variety of reciprocal flaps used for closing circular defects or with a single-lobed flap. One should submit all removed specimens for dermatopathology confirmation of the diagnosis of dermatofibroma.
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