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Dermatology Diagnosis

When A Patient Presents With A Painless Lesion On The Plantar Foot She Has Had For ‘At Least 20 Years’

A 63-year-old female presented to the office with a chief complaint of a painful right second toe. She said the toe rubbed on her shoe. The patient noted that she tried using corn-removing plaster, which made the toe worse. She had a secondary complaint of a non-painful skin growth on the bottom of her foot near the big toe joint. She related no prior treatment for the skin growth. She denied any bleeding or recent changes in the appearance of the skin growth The lesion did not itch or have any scaling. She had no specific recollection of the duration of the lesion but thought she had it for “at least 20 years.” 

Her past medical history was remarkable for Hepatitis A in 1978. She did not take any prescription medications. The patient’s past surgical history included a total knee replacement. She denied any tobacco use or alcohol abuse. 

Her physical examination revealed strong palpable pulses at +2/4 for the dorsalis pedis and posterior tibial arteries bilaterally. The neurologic exam revealed symmetric deep tendon reflexes and epicritic sensation intact to the level of the toes. The dermatologic examination revealed skin texture, turgor and temperature within normal limits. Mild ankle peripheral edema was present with 1+ pitting. 

Evaluation of the plantar right foot revealed a pedunculated skin growth with a verrucous appearance measuring 4 mm x 7 mm x 2 mm (protrusion). There were six stemmed lesions within the skin growth. Two to three tiny satellite lesions were evident proximal and medial to the main lesion (see photo above). The color of the skin lesions were red/purple. There was also a macerated area of skin with shallow ulceration overlying the proximal interphalangeal joint of the right second toe (due to salicylic acid use). An orthopedic examination revealed a hammertoe deformity of the right second toe. Otherwise, the patient had pain-free range of motion of the ankle and foot bilaterally. 

Key Questions To Consider

1. What are important diagnostic characteristics of this plantar lesion? 

2. What is the differential diagnosis for this lesion? 

3. How should one go about ascertaining a definitive diagnosis? 

4. What are the possible treatment options for this type of lesion? 

Answering The Key Diagnostic Questions

1. It is important to characterize primary and secondary lesions along with color, size, demarcation and location. 

2. The differential diagnoses include verruca plantaris, acral fibrokeratoma, angiokeratoma, verrucous hemangioma and carcinomas. 

3. Excisional biopsy in this case will likely reveal a definitive diagnosis. 

4. The treatment of larger lesions involves excision with a wide margin. In smaller lesions like the ones this patient has, cryosurgery, electrocautery or laser therapy are possible. However, excision is more likely to prevent recurrence.

Working Through The Differential Diagnosis 

When evaluating a skin lesion, it is important to describe it accurately. The basic language of dermatology includes primary lesions, secondary lesions, color and size. Non-fluid filled primary lesions include, for example, macules, papules, plaques, patches and nodules. Secondary lesions include lichenifications, crusts, erosions/ulcerations and scaling. The color of lesions can be white, yellow, brown, red, purple, blue or black. It is also important to determine if the lesion is well-demarcated or not. Location of skin lesions is also important to consider as certain lesions have a propensity to occur in certain regions. 

This patient presented with a well-demarcated cluster of red/purple-colored pedunculated (stalk/finger-like) primary lesions with a verrucous appearance. I also noted tiny satellite lesions proximal and medial to the main lesion. There were no secondary lesions. The size of the main lesion was less than 1 cm in diameter. 

The differential diagnoses for this lesion include verruca plantaris, acral fibrokeratoma, angiokeratoma, verrucous hemangioma and carcinomas. 

Verruca plantaris is the obvious first differential diagnosis as podiatrists see this on a regular basis. Experience tells us that verrucae can have many different “looks.” Verrucae may be in clusters or appear as a solitary lesion. Verrucae can also occur bilaterally. Shaving the top layer may reveal the telltale sign of pinpoint bleeding. Often times, though, there are no hemorrhagic black dots or pinpoint bleeding upon debridement, which complicates forming a diagnosis. 

Acral fibrokeratoma is a benign skin growth, which has an either sessile or pedunculated appearance. The color of these lesions is usually skin-colored to red. Acral fibrokeratomas are relatively rare on feet and more likely to occur on the hand. When the lesions affect the foot, they typically do so on the great toe.1 

Angiokeratomas are most common in older adults. These lesions have a verrucous look and can be dark red to black in color. These lesions typically appear on the legs with presumed growth from prior trauma. Angiokeratomas are often associated with rare hereditary diseases such as Fabry disease and angiokeratoma of Mibelli.

Verrucous hemangioma is a relatively rare capillary or cavernous hemangioma, which may develop a verrucous or hyperkeratotic appearance. The lesions are unilateral, well-demarcated and typically affect the lower extremities. Lesions can develop in childhood or later in adulthood. The lesions can measure between four mm and eight cm.3 

Squamous carcinoma and amelanotic melanoma are great masqueraders of other benign skin lesions. Due to the seriousness of these lesions, one must be sure to rule them out during the diagnostic process. 

As with many skin lesions with an uncertain clinical diagnosis, biopsy is the method by which one makes a final diagnosis. In this case, the visual appearance of the lesion was warty and fibrous. Your initial impression might be that it is not a wart due to the lack of hemorrhagic spots and looks more like a fibroma. Therefore, fibrokeratoma may be a clinician’s first impression. 

What The Excisional Biopsy Revealed 

After an excisional biopsy, the pathologist described the findings as hyperkeratosis, papillomatosis and acanthosis of the epidermis. There were thin-walled, dilated blood-filled spaces in the superficial dermis. The correct diagnosis is therefore verrucous hemangioma. The main pathological difference between a verrucous hemangioma and angiokeratoma is the depth of the involved dermis. With angiokeratomas, the lesions are more superficial within the dermis whereas verrucous hemangiomas can develop deeper in the dermis and subcutaneous tissues.

The treatment of larger verrucous hemangiomas involves excision of the lesion with a wide margin. In smaller lesions like the ones for this patient, cryosurgery, electrocautery or laser therapy are possible. However, excision is more likely to prevent recurrence. With wide excision extending into the subcutaneous tissues, recurrence is uncommon.

Final Notes 

In conclusion, this case study was particularly interesting due to a skin lesion with the clinical appearance of both a fibroma and a wart. The diagnosis was possible with excisional biopsy. “All that glitters is not gold” is a line from Shakespeare’s The Merchant of Venice. In a similar respect, just because a skin lesion looks like a wart, it does not mean it is a wart.  

Dr. Fishco is board-certified in foot surgery and reconstructive rearfoot and ankle surgery by the American Board of Podiatric Surgery. He is a Fellow of the American College of Foot and Ankle Surgery, and a faculty member of the Podiatry Institute. Dr. Fishco is in private practice in Phoenix. 

Dermatology Diagnosis
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By William Fishco, DPM, FACFAS
References

1. Tower DE, Hammond JR. Acral fibrokeratoma: a rare pedal soft-tissue mass. J Am Podiatr Med Assoc. 2018;108(2):172–177. 

2. Wang L, Gao T, Wang G. Solitary angiokeratoma on palms and soles: a clinicopathological analysis of 21 cases. J Dermatol. 2013;40(8):653-656. 

3. Wang G, Li C, Gao T. Verrucous hemangioma. Int J Dermatol. 2004;43(10):745-746. 

4. Koc M, Kavala M, Kocaturk E. An unusual vascular tumor: verrucous hemangioma. Dermatol Online J. 2009;15(11):7. 

5. Laun K, Laun J, Smith D. Verrucous hemangioma. Eplasty. Available at: https://www.ncbi. nlm.nih.gov/pmc/articles/PMC6328935/ . Published January 7, 2019. Accessed November 6, 2020. 

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