When A Plantar Pigmented Lesion Increases In Size With Irregular Borders And Drainage

A 61-year-old male with diabetes presents to the clinic reporting a mole on the bottom of his right foot that had increased in size over the past five months. The area is not painful but the patient has a history of peripheral neuropathy. There is no history of trauma. Within the past one to two weeks, the patient noticed some bloody drainage from the area on his sock. The patient denies any difficulty breathing, pruritus, fever, nausea, vomiting, diarrhea or leg pain.

The patient reports no travel within the past year. There is no change in medications, laundry detergent or lotion use.

There is a solitary brown to black macular pigmented lesion on the plantar fifth metatarsal base region of the right foot, measuring approximately 5.4 cm. The color varies from pitch black in the center to light brown/black at the periphery. The borders are irregular. At the center of the lesion is a full-thickness ulceration with a depth of 3 mm. It does not probe to bone. There is no erythema, malodor, lymphangitis or purulence. Popliteal and inguinal lymph nodes are not palpable. His vital signs are normal, outside of slightly elevated blood pressure.

Key Questions To Consider

1) What are the basic questions to ask regarding a pigmented lesion?
2) What is the most likely diagnosis?
3) What are some differential diagnoses?
4) What is the appropriate workup in this situation?
5) What is the necessary treatment for this diagnosis?

Answering The Key Diagnostic Questions
1) Is there any personal or family history of malignancy?
2) The most likely diagnosis is malignant melanoma.
3) Differential diagnoses include angiokeratoma, traumatic hematoma, hemangioma, dermatofibroma, venous lake, blue nevus, lentigo, pigmented basal cell carcinoma and traumatized nevus.
4) The workup begins after confirming the results through the pathology report of the punch biopsy or excision of the lesion. Lab work should include a complete blood cell count and a comprehensive metabolic panel. Order a chest X-ray as well as advanced imaging scans that can include magnetic resonance imaging (MRI), ultrasound (indicating lymph node involvement) and positron emission tomography/computed tomography (PET/CT).¹
5) Preferred treatment is surgical excision of the lesion versus a 5-6 mm punch biopsy into the subcutaneous fat. If one confirms melanoma, wide excision is necessary (1 cm margins for a 1 mm thick lesion and 2 cm margins for those greater than 1 mm).^1,2 Consult with general surgery (for sentinel node biopsy) and oncology (further workup and treatment) upon the malignancy diagnosis.

A Closer Look At Malignant Melanoma
The most likely diagnosis for this patient is malignant melanoma. It is a malignant tumor of the melanocytes that reside within the basal layer of the epidermis and can metastasize to any organ after invading the dermis. Melanomas can occur in or around an existing nevus or de novo. Intense sunburns create more of a risk for melanomas than consistent exposure to the sun, which is more commonly associated with basal cell carcinomas. However, lentigo maligna melanoma is an exception because many of these lesions are on the head and neck.

Melanoma occurs almost exclusively in adults, being the eighth most common cancer in the United States and causing 1 to 2 percent of all cancer deaths.³ Melanoma is more common in Caucasians than African-Americans and Asians, and men have a slightly higher rate of melanoma than women. The average age for diagnosis is 57 years old.

There are four types of malignant melanoma pertinent to the foot. They include superficial spreading melanoma, lentigo maligna melanoma, nodular melanoma and acral lentiginous melanoma.

Superficial spreading melanoma. This type comprises roughly 70 percent of malignant melanoma. Superficial spreading melanoma consists of macular to papular lesions with abnormal borders and typically arises from existing nevus.⁴ Superficial spreading melanoma can be present anywhere on the body but is more common on the trunk of males and legs of females.

Lentigo maligna melanoma. About 10 to 15 percent of malignant melanoma is lentigo maligna, which is due to sun exposure.⁵ It may be years before lentigo maligna becomes invasive and it is more common in people over 60.¹ People with this type of melanoma may have areas of hypopigmentation.

Nodular melanoma. Comprising 10 to 15 percent of malignant melanoma, nodular melanoma may appear as a blood vessel growth. It is invasive early with ulceration common and appearing as dark brown to black in color.⁴ Radial growth may not be noticeable because vertical invasion occurs early (aggressive lesion). About 5 percent of nodular melanomas may be amelanotic melanomas. There is a predilection for the backs of males although these lesions can be on any body area.

Acral lentiginous melanoma. This type comprises about 5 to 8 percent of malignant melanoma and is most common in dark-skinned individuals, occurring on the palms, soles and nail beds. A Hutchinson’s sign reveals pigment changes in the eponychium due to pigment from a subungual melanoma. Acral lentiginous melanoma appears as a dark band in the nail.^4,6 There is vertical invasion early (aggressive lesion).

When it comes to assessing pigmented lesions that are suspicious for malignant melanoma, one can use the ABCD evaluation. Asymmetry, Border irregularity, Color variation and a Diameter of > 6 mm should be cause for concern.⁴

Approximately 70 percent of malignant melanomas arise de novo so changes are easier to appreciate.⁴ The rest develop from already existing junctional nevi and the patient may not notice changes in these lesions as much.

A Quick Overview Of Melanoma Staging
The most complete staging method is by the American Joint Committee on Cancer from 2010.⁷

1) Clark (level of invasion)
Stage I = tumor cells above basement membrane (in situ)
Stage II = into papillary dermis
Stage III = between papillary dermis and reticular dermis
Stage IV = into reticular dermis
Stage V = into subcutaneous tissue

2) Breslow (thickness)
Stage I = less than or equal to 0.75 mm
Stage II = 0.76-1.5 mm
Stage III = 1.51-2.25 mm
Stage IV = 2.26-3 mm
Stage V = greater than 3 mm

Current Insights On Making A Differential Diagnosis
Angiokeratoma. This features a vascular tumor that can be difficult to differentiate from malignant melanoma. Angiokeratomas are dilated blood vessels with overlying hyperkeratosis and red to blue coloration.⁸

Traumatic hematoma. This may appear similar to a malignant melanoma but typically resolves in seven to 14 days.

Hemangioma. Hemangiomas are compressible and stable lesions. They are dilated blood vessels and endothelial cells that commonly present on lower legs and toes. They appear with a bright red (cherry hemangioma) to purple color. Treatment is not needed.

Dermatofibroma. These are firm growths of fibrous histiocytes that appear as a “button hole” when pinched. They are typically asymptomatic and often present on legs and toes. Dermatofibromas have a raised ovular to circular appearance. They are usually smooth but can be hyperkeratotic or scaling.

Venous lake. These lesions have a blue color and are compressible. Venous lake lesions are papular with dilated venules and capillaries. They usually arise on the face, ears and lips in the elderly.

Blue nevus. A blue nevus is an acquired benign papular lesion with dark pigmentation from dermal melanocytes. It is commonly present on the feet and hands. Treatment is not needed unless there are cosmesis concerns or a change in appearance.

Lentigo. A lentigo is a benign pigmented lesion appearing on sun-exposed skin.⁵ It is symmetric with even pigmentation. Melanocytes of this lesion reside within the basal cell layer of the epidermis.

Pigmented basal cell carcinoma. The borders of this carcinoma appear wax-like with telangiectasias. The center may be ulcerative with a pigmented border.

Traumatized nevus. This returns to its original state in seven to 14 days.

Keys To A Thorough Workup And Treatment
Excisional biopsy is preferable but one can also perform a 5-6 mm punch biopsy into the subcutaneous fat. The pathologist should be aware of the lesion size and morphology as well as any personal or family history of malignancy. Confirmation of malignancy should initiate an immediate consultation with oncology and general surgery to coordinate the plan of care for the patient. One should also notify the patient’s primary care physician.

Order chest X-rays. General surgeons can perform a sentinel node biopsy before wide excision of the lesion. (A sentinel node biopsy is not common for lesions less than 1 mm thick). The reasoning for this is to avoid a disturbance of the dermal lymphatics that happens with an excisional biopsy. A positive sentinel node biopsy results in excision of lymph nodes in the affected area.

The current recommendations for wide excision are 1 cm margins for lesions less than 1 mm thick and 2 cm margins for lesions greater than 1 mm thick.²

The pathologist’s report should include tumor thickness (Breslow scale, most commonly associated with survival status), level of invasion (Clark scale), growth pattern, margin status (clean versus still present), dimensions, and whether it is ulcerative or not. Reports should utilize the American Joint Committee on Cancer staging system for the most accuracy.⁷

This specific patient had a positive punch biopsy and subsequently had a sentinel lymph node biopsy with general surgery and subsequent wide excision of the lesion with 2 cm margins during the same operation by podiatry. The sentinel lymph node biopsy was negative. The patient is in ongoing wound care. After the wide excision, the initial wound measuring 10 x 9 cm was reduced down to 5 x 2.5 cm in size. He has had treatment with Neox (Amniox Medical) applications and TransCu (EO2 Concepts) continuous diffusion of oxygen adjunctively. Several return trips to the OR for surgical debridement have occurred along the way.

Melanoma patients need to have regular follow-up appointments as 8 percent of these patients develop another melanoma within two years. The frequency of these appointments varies but they should be every three to six months during the first three years after the initial diagnosis and every six to 12 months after that.

Remember that you may be the only one looking at your patient’s feet. Some patients do not remove their shoes during exams by primary care physicians and some patients may not check their own feet. Noticing changes in nevi at follow-up appointments and taking a biopsy of the lesion can potentially be life-saving for your patients.

Dr. Couture is affiliated with the Central Texas Veterans Health Care System in Temple, Texas.

References

1. Albu C, Albu D, Alexandru A, et al. Diagnosis and treatment protocols of cutaneous melanoma: latest approach 2010. Chirurgia. 2010; 105(5):637-643.
2. Ascierto P, Bono R, Chiarion-Sileni V, et al. Surgical management of suspicious melanocytic lesions in Italy. Dermatology. 2013; 226(suppl 1):18-21.
3. American Cancer Society. Cancer Facts & Figures 2014. Available at www.cancer.org/acs/groups/content/@research/documents/webcontent/acspc-042151.pdf  . Accessed June 2, 2014.
4. Dockery G. Cutaneous Disorders of the Lower Extremity, W.B. Saunders, Philadelphia, 1997, pp. 227-232.
5. Hinnen J, Juten P. A 71 year-old woman with a pigmented nail bed, which persisted after trauma. Acta Chir Belg. 2010; 110(4):475-478.
6. Chung K, Jung J, Lee S, Nam K, Roh H. Comparison of secondary intention healing and full-thickness skin graft after excision of acral lentiginous melanoma on foot. Dermatol Surg. 2011; 37(9):1245-1251.
7. American Joint Committee on Cancer (AJCC) Staging of Melanoma. In: Edge SB, Byrd DR, Compton CC, et al (eds.) AJCC Cancer Staging Manual, Seventh Edition. Springer Publishing, New York, 2010, pp. 325-344.
8. Dancho J, Dumitrache N, Martin B, Neiderer K. Angiokeratoma presenting as a melanoma. J Am Podiatr Med Assoc. 2013; 103(3):241-242.

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