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Diagnosing And Treating A Large Nevus With Irregular Borders On The Back Of The Heel
A 38-year-old African-American male presented to the clinic with a complaint of a painful callus on his left fifth digit. On examination, however, there was a large nevus with irregular borders on the back of his right heel. Upon questioning, the patient stated he thought it had been there for a long time and wasn’t changing, but he wasn’t sure. He had no personal or family history of skin cancer.
The lesion wasn’t pruritic or painful. Despite its large size (approximately 2 cm) and irregular borders, it was a homogenous dark brown color with no elevation and no surrounding erythema or irritation. The patient had no other lesions anywhere else.
The lesion on his left fifth digit turned out to be a simple callus that he had been incorrectly treating with salicylic acid pads. However, the lesion on his heel was somewhat more concerning. After a discussion about the risks of larger dark lesions with irregular borders and the relative ease of performing a biopsy, the patient decided he wanted the lesion biopsied to be sure it wasn’t anything cancerous. Accordingly, I performed a 3.5 mm punch biopsy in the darkest part of the lesion.
Key Questions To Consider
1. What the diagnosis?
2. What is the prognosis for these lesions?
3. When should you consider a biopsy?
4. What is the best way to treat these lesions if necessary?
Answering The Key Diagnostic Questions
1. The diagnosis is lentigo.
2. Lentigines are completely benign and have no malignant potential as opposed to melanomas.
3. The ABCs of melanoma can be helpful in determining the need for biopsy.
4. Treatment options include laser therapy, cryotherapy, topical creams and ointments, chemical peels, and surgical removal.
What You Should Know About Lentigines
Pathology reported the lesion to be a lentigo. Lentigines are benign, pigmented macules/patches resulting from increased activity of epidermal melanocytes.
There are two types: simple and solar. Simple lentigines occur in children, are usually less than 5 mm in diameter and have no predilection for sun-exposed areas. A solar lentigo, as its name implies, occurs on the sun-exposed areas of the skin, mainly in adults. This particular lesion affects more than 90 percent of Caucasians over the age of 60 and can reach sizes of greater than 1 cm. This can make it difficult to differentiate it from melanoma. In these cases, a biopsy is warranted to rule out malignancy.1
Differentiating Lentigo From Acral Lentiginous Melanoma
While it is common to have simple lentigines (a benign acral lentigo) on the plantar foot, podiatric physicians must differentiate this from the malignant version acral lentiginous melanoma. This form of melanoma accounts for only 3 to 5 percent of all cutaneous melanomas but has a poor prognosis, probably due to delays in treatment. It is the most common type of melanoma in darker-skinned individuals such as African-Americans, Asians and Hispanics.2
These lesions have a tendency to stay flat but will still have darker colors and large irregular borders. They can also have areas of elevation, which one should biopsy along with any acquired lesions greater than 6 mm in diameter.3 Acral lentiginous melanoma does include subungual melanoma, which will present as a dark longitudinal band or diffuse pigmentation of the nail. Hutchinson’s sign involves spread to the nail fold.2
When To Biopsy Lesions
When should the podiatric physician be concerned enough to do a biopsy of a lesion and what is the best method of doing so? Remember the ABCs of melanoma or, more appropriately, the ABCDEFs.2
A is for Asymmetry, meaning the lesion isn’t the same throughout.
B is for Borders, which shouldn’t be irregular or notched.
C is for Color. Shades of red, white, blues and blacks are more concerning.
D is for Diameter. Any lesion greater than 6 mm is concerning.
E is for Evolving. Any changing lesion raises suspicion of malignancy.
F is for Family or personal history of skin cancer.
With subungual melanoma, the ABCs still apply but in a somewhat different manner.2
A is for Age. Patients in their fifth to seventh decades have the highest incidence.
B is for Brown/Black discoloration with a breadth of 3 mm or greater.
C is for Change in the nail plate or lack of change with treatment.
D is for the Digit most commonly affected, the hallux.
E is for Extension of pigment onto the proximal or lateral nail fold (Hutchinson’s sign).
F is for Family or personal history of skin cancer.
When doing a biopsy of a suspicious lesion, the goal is determining the diagnosis so the surgeon or consulting physician can determine what type of resection is necessary, whether it be local, wide or radical. Therefore, one should perform the biopsy in a way that gives the dermatopathologist the best chance of determining the correct diagnosis. If one can biopsy the entire lesion, this is best as it increases the chances that the dermatopathologist will be able to find the malignant cells.
In larger lesions, however, this may not be possible or practical. Excising a large lesion and doing a complicated skin flap just to find out it was a nevus is a little excessive. Therefore, in larger lesions, biopsy the “ugliest” part of the lesion as it is the most likely location of any existing malignant cells. Sometimes, this may require multiple biopsies, which is both justifiable and billable.4,5
Frequently on the plantar foot, a superficial biopsy will not be enough due to the thickness of the plantar skin. In order to get a sufficient sample, a punch or other more invasive biopsy will be required (in comparison to a superficial shave biopsy or curettage).
A Guide To Treating Lentigines
Lentigines are completely benign and have no malignant potential. Therefore, they do not require treatment. However, many patients have cosmetic concerns and desire treatment/removal. There are many available treatment options, including laser therapy, cryotherapy, topical creams and ointments, chemical peels, and even surgical removal. Obviously, excising the lesion via surgical removal or biopsy is the best way to guarantee resolution, and smaller lesions are very amenable to this. However, given that this is mostly a cosmetic concern, patients may be hesitant to trade an ugly lentigo for an ugly scar. Cryotherapy raises the same concern but cryotherapy continues to be the most common method of removal as it is convenient and effective.6
Laser therapy is very effective and safe for the removal of lentigines. Researchers have demonstrated that lasers are effective for lesions with increased vascularity and studies have shown that a solar lentigo is just such a lesion.7 There are multiple types of lasers that are effective in the treatment of lentigines but Nd:YAG lasers seem to be the most effective. In one study by Vachiramon and colleagues in 2016, a Q-switched Nd:YAG laser cleared almost 50 percent of lesions in 12 weeks with just one treatment in comparison to a fractional CO2 laser, which only cleared 4 percent of lesions in the same time.6 Other studies have achieved similar results with Q-switched Nd:YAG lasers.8
The problem with laser therapy lies in the pain associated with its use and with its tendency to cause post-inflammatory hyperpigmentation. Emla creams (lidocaine 2.5% and prilocaine 2.5%) and post-treatment cooling regimens may decrease the associated pain, and authors have suggested 4% topical pidobenzone as a possible adjunctive therapy to decrease the incidence of post-inflammatory hyperpigmentation.9
There are also various topical products that have had mixed success in treating lentigines. These products include hydroquinone, hydroxy acid, tretinoin, tazarotene and steroids.3,6 One study by Imhof in 2016 compared the results of a Q-switched ruby laser and a triple combination skin-lightening cream consisting of 5% hydroquinone, 0.03% tretinoin and dexamethasone in the treatment of solar lentigines in 15 patients.10 Not only was the laser treatment superior as far as its lightening effects go but it was faster and had a longer-lasting effect than the cream. However, both treatments had acceptable results and minimal side effects.
For those looking for a more naturopathic method of cure, plant-based products such as green tea, coffee fruit, soy beans, licorice, milk thistle, grape seed extract and more are suggested treatments for lentigines. These natural products contain various flavonoids and other antioxidants that in theory have a lightening effect on hyperpigmented lesions such as solar lentigines. A recent systematic review by Fisk and coworkers examined 29 articles on this subject.11 The authors found mixed results from studies that were flawed in design and suggested that further research is needed.
In Conclusion
Lentigines are pigmented lesions that arise from increased activity of epidermal melanocytes. They are completely benign and have no malignant potential although they can be difficult to differentiate from melanoma at times, and therefore may require biopsy to be sure. If one confirms the diagnosis to be benign, however, treatment is not necessary unless the patient desires it for cosmetic reasons. Although cryotherapy is the most frequent method of treatment, laser therapy is very effective and safe, and has minimal side effects. Additionally, there are various topical and plant-based products that have mixed results but are convenient and, for the most part, painless.
Dr. Vella is in private practice in Gilbert, Ariz.
References
1. Schaffer JV, Bolognia JL. Benign pigmented skin lesions other than melanocytic nevi (moles). UpToDate. Available at https://www.uptodate.com/contents/benign-pigmented-skin-lesions-other-than-melanocytic-nevi-moles . Published March 6, 2017.
2. Vlahovic TC, Schleicher SM. Skin Disease of the Lower Extremities: A Photographic Guide. Ch. 9: Benign and Malignant Lesions. HMP Communications, Malvern, Pa., 2012, p. 90.
3. Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy, Fifth Edition, Ch. 19: Light-Related Diseases and Disorders of Pigmentation. Mosby Elsevier, St. Louis, p. 772.
4. Bakotic B. Biopsy planning and post-biopsy tissue handling: a synopsis. Podiatry Management. 2009; 4:89-100.
5. Bakotic B. Coding Summary for Biopsy Techniques. BakoPathology.com. Available at https://bakocts.com/biopsy-planning-and-post-biopsy-tissue-handling-a-synopsis/ .
6. Vachiramon V, Panmanee W, Techapichetvanich T, et al. Comparison of Q-switched Nd: YAG laser and fractional carbon dioxide laser for the treatment of solar lentigines in Asians. Lasers Surg Med. 2016; 48(4):354-359.
7. Hasegawa K, Fujiwara R, Sato K, et al. Increased blood flow and vasculature in solar lentigo. J Dermatol. 2016; 43(10):1209-1213.
8. Kaminaka C, Furukawa F, Yamamoto Y. The clinical and histological effect of a low-fluence Q-switched 1,064-nm neodymium: yttrium-aluminum-garnet laser for the treatment of melasma and solar lentigo in Asians: prospective, randomized, and split-face comparative study. Dermatol Surg. 2017; 43(9):1120-33.
9. Campanati A, Giannoni M, Scalise A, et al. Efficacy and safety of topical pidobenzone 4% as adjuvant treatment for solar lentigines: result of a randomized, controlled, clinical trial. Dermatology. 2016; 232(4):478-83.
10. Imhof LL. A Prospective trial comparing q-switched ruby laser and a triple combination skin-lightening cream in the treatment of solar lentigines. Dermatol Surg. 2016; 42(7):853-857.
11. Fisk WA, Agbai O, Lev-Tov HA, et al. The use of botanically derived agents for hyperpigmentation: A systematic review. J Am Acad Dermatol. 2014; 70(2):352-365.
