Differentiating Non-Pigmented Tumors In The Lower Extremity

Tracey C. Vlahovic, DPM

Given the high stakes in diagnosing potentially dangerous lower extremity tumors, having a clear idea of the clinical presentation is vital. This author uses several case studies to demonstrate the effective diagnosis and treatment of non-pigmented tumors.

   Flesh colored lesions anywhere on the body can pose a diagnostic challenge. They typically are the “zebras” in a field of horses. In other words, they are uncommon but one should think of them on a regular basis when a lesion presents as unusual or not responding to common therapies.

   On the lower extremity, a delay in diagnosis for a lesion such as amelanotic melanoma can be devastating for both the patient and practitioner. This article will address both benign and malignant non-pigmented tumors of the lower extremity.

What You Should Know About Dermatofibromas

   Dermatofibromas, which most commonly occur on the lower extremities, are flesh-colored, dome-shaped papules or nodules that are firm to the touch.1 They can occasionally be pigmented but often will be tan to pink. Pinching them in toward their center will cause them to umbilicate (i.e. the “dimple sign”).2 These lesions typically occur on the anterior tibia in females and are usually asymptomatic. Patients have reported pain, making dermatofibromas the most painful of skin lesions when this does occur.3 The patient may complain that the site was originally an insect bite or a cut, but in reality, a dermatofibroma’s origin is truly unknown.

   Histologically, dermatofibromas are a nodular proliferation of fibroblasts in the reticular dermis with overlying hyperplasia of the epidermis.1 Clinically, they may resemble a scar, a keloid or the malignant dermatofibrosarcoma protuberans and nodular Kaposi’s sarcoma. Dermatofibromas are usually solitary lesions but they can also occur in clusters in patients who are immunocompromised.

   Treatment consists of complete excision or leaving the lesion alone. Due to the lesion’s typical location of the anterior tibia and the scarring potential there, most physicians opt to excise only if clinical signs and symptoms warrant it. In this case, the scar can be worse cosmetically than the original nodular lesion. However, some patients prefer the scar over the original protrusion.

Inside Insights On Fibromas

   Fibromas, also known as cutaneous angiofibromas, are firm, smooth skin-colored exophytic columns that usually extend from the nail unit. If present dorsally on the nail plate, fibromas will cause a vertical depression in the nail plate that can reverse once one removes the lesion. Fibromas can also arise plantar to the nail plate at the hyponychium. One would see solitary lesions in adults. Multiple lesions (called Koenen’s tumors) in and around the nail unit at puberty are linked to tuberous sclerosis. Differential diagnoses include verrucae, skin tags and nevi.

   Treatment of the problematic fibroma typically consists of excision although recurrence rates are high. Researchers have described treatment with both electrodesiccation and a CO2 laser post-excision, but the nail plate and surrounding tissue may be damaged with these modalities.4 Application of phenol to the area of the excised fibroma has been a successful treatment both cosmetically and clinically.4 One simply shaves the fibroma and applies phenol without removing the nail plate, thus protecting the nail matrix.

How To Treat Digital Mucous Cysts

   Digital mucous cysts (cutaneous myxoid cysts) occur on the dorsal surface of the distal phalanx and ultimately result in a longitudinal depression in the nail plate.5 Differential diagnoses to consider are: fibroma, rheumatoid nodule and giant cell tumor of the tendon sheath. The etiology is unknown and pain is uncommon in most cases.

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