Melanoma—or Mimic?

Authors: 

STEVEN Q. WANG, MD

The incidence of malignant melanoma has been rising at an alarming rate.1,2 There is still no cure for metastatic melanoma; thus, early diagnosis followed by prompt excision is essential for a good prognosis.

For early detection of skin cancers, every patient should undergo a careful total-body skin examination at least once a year. Thorough examination of the entire body, including the scalp, toes, and plantar surface of the feet, in a well-lit environment is crucial. Examine patients who are at higher risk for melanoma more frequently (every 3 to 6 months). Such patients include those with blond hair, fair skin, blue eyes, a history of numerous sunburns, atypical nevi, and a personal or family history of melanoma. To help prevent melanoma, advise all patients to avoid or limit sun exposure and to use sunscreen frequently.

The ABCD rule (asymmetry, border irregularity, color variegation, and diameter greater than 6 mm) can help distinguish melanomas and worrisome atypical nevi from benign pigmented lesions.3 To improve diagnostic accuracy, dermoscopy (also known as dermatoscopy or epiluminescence microscopy) may be used to examine suspicious lesions.4 Like an otoscope or ophthalmoscope, a dermoscope has an internal light source and a magnification of at least 310, which allows the user to see detailed structures in the skin that are not visible to the naked eye. Biopsy is required for suspicious lesions.

In this Photo Essay, I present 5 cases of pigmented lesions--one of which is malignant.


 

 


Pigmented, Pruritic Macule

A 59-year-old man presented for evaluation of a pigmented, occasionally pruritic lesion on the right side of his lower back. The lesion had been present for at least 5 years and had enlarged.

The lesion featured 3 colors (black, brown, and tan), was more than 6 mm in diameter, and had a mild degree of asymmetry. Dermoscopic examination revealed comedolike openings (green circles) and milialike cysts (orange circles)--2 specific structures seen mainly in seborrheic keratosis. Furthermore, the lack of a pigmented network indicated that this was not a melanocytic lesion (eg, an atypical nevus or melanoma).

Although the patient was reassured that the lesion was benign, he chose to have it removed. A shave biopsy was performed. Histologic analysis of the biopsy specimen showed acanthosis and pseudohorn cysts in the epidermis, which confirmed the diagnosis of pigmented seborrheic keratosis.

This highly prevalent, benign skin lesion is commonly found on the trunk and face. It is especially common in elderly persons. Most seborrheic keratoses are tan or light brown and have a waxy, stuck-on appearance. However, a significant proportion can mimic melanoma.

In most patients, treatment is for cosmesis only.
 


 

 

Multicolored Nodule
Fearing that the dark "mole" on her left lower leg might be cancerous, a 43-year-old woman with a history of nonmelanoma skin cancer sought medical attention. The lesion had been present for 3 months, had enlarged, and was occasionally tender after shaving.

The clinical diagnosis was dermatofibroma. This benign skin lesion is commonly found on the legs of women. The cause is unknown, although trauma from shaving or insect bites has been implicated. Most dermatofibromas present as a semifirm nodule or papule and can be easily diagnosed, especially when the lesion demonstrates the characteristic dimple sign; however, a fair proportion of these lesions can resemble melanomas.

Although this lesion measured 6 mm and was a worrisome red-dark brown, it demonstrated the dimple sign. In addition, examination with a dermoscope revealed a central hypopigmented and structureless area (green dots) surrounded by a faintly pigmented network (orange rectangles) at the periphery--the classic dermoscopic pattern of a dermatofibroma. Histologically, the central structureless area corresponds to the fibrosis in the mid-dermis of the dermatofibroma, and the peripheral network can be attributed to the epidermal induction and the downward extension of the rete ridges in the epidermis.

Most dermatofibromas are asymptomatic; no treatment is needed. However, painful or itchy lesions can be excised or treated with liquid nitrogen. This patient decided to have the lesion removed.
 



Dark, Irregular Lesion in a Golfer

This pigmented lesion was noted on the posterior neck of a 76-year-old man during his yearly skin examination. The patient—an avid golfer who spends every winter in Florida--frequently wears hats and uses sunscreen. He had a number of actinic keratoses that were treated with liquid nitrogen, but he had no history of skin cancer.

The irregularly shaped lesion had focal erythema and black foci. However, on dermoscopic examination, the absence of pigmented networks indicated a nonmelanocytic lesion. Further examination revealed arborizing vessels (green arrow), spoke wheel-like areas (blue circle), and blotches (white circle). This combination of features is characteristic of basal cell carcinoma (BCC). This common skin cancer is typically located on sun-exposed areas, such as the face, nose, ears, trunk, and neck.

A shave biopsy was performed. Histologic analysis showed basaloid collections of cells at the dermoepidermal junctions, with the characteristic cleft formation. These findings confirmed the diagnosis of BCC.

The clinical appearance of this lesion was certainly not typical of BCC. Most BCCs are pearly and translucent, with overlying telangiectasia; however, pigmented BCCs can mimic melanomas.

Treatment options include standard excision, Mohs surgery, and application of imiquimod (for superficial BCC only). This patient underwent Mohs surgery. Three years later, the cancer had not recurred.
 


Melanoma Look-alike?
A 36-year-old man presented for his semiannual skin examination with concerns about a mole on his abdomen that had darkened. He had multiple atypical nevi but no personal or family history of skin cancer. In adolescence, he had had many severe sunburns. He routinely uses sunscreen and avoids the sun when possible.

The lesion was asymmetric, light and dark brown, and 7 mm in diameter. On dermoscopic examination, the lesion had thick, broad, and irregular pigmented networks (blue circle) and branched streaks. However, it lacked other worrisome features associated with melanoma, such as blue-gray veils. (The linear black structures dispersed throughout the pigmented networks are hair shafts.)

Results of an 8-mm punch biopsy showed features of an atypical nevus: irregular proliferation of nests at the dermoepidermal junction, bridging of the rete ridges, and fibroplasia.

Atypical nevi are significant melanocytic lesions. Although they are benign, these lesions resemble melanomas clinically and fulfill most, if not all, of the ABCD criteria. Furthermore, persons with atypical nevi are at higher risk for melanoma.

Atypical nevi may require frequent monitoring or standard excision. In this patient, the entire mole was removed because of the risk of malignancy.



Suspicious Asymptomatic Mole

At the prompting of his wife, a 31-year-old man decided to have a pigmented lesion on his left upper thigh evaluated. The lesion had been present for a long time and was asymptomatic. The patient had no history of sunburns and spent most of his time working indoors.

The lesion fulfilled all the ABCD criteria. It was asymmetric and more than 6 mm in diameter, and it had multiple colors and irregular borders. Dermoscopic examination showed irregular pigmented networks (blue circles) at the periphery, focal hyperpigmented blotches (white circle), and a blue-gray veil (red circle) in the center. The dermoscopic finding of a blue-gray veil is highly specific for invasive melanoma.The patient's lesion was excised. Histologic analysis of a biopsy specimen showed pagetoid spread in the epidermis and contiguous growth of atypical melanocytes in the dermis. Most of the cells had a high nucleus-to-cytoplasm ratio. Numerous mitoses were noted. These findings confirmed the diagnosis of invasive melanoma.

Treatment of local melanoma (stage I malignant melanoma) is standard excision with the appropriate margin control. For in situ malignant melanoma, the standard margin is 0.5 cm. The choice of treatment for invasive melanoma is based on the Breslow thickness; the margin varies depending on the thickness.

This patient's lesion was excised. He did not require adjuvant chemotherapy or sentinel node biopsy.

 

References: 

1. Koh HK. Cutaneous melanoma. N Engl J Med. 1991;325:171-182.
2. Ernstoff MS. Melanoma. Screening and education. Clin Plast Surg. 2000;27: 317-322, vii.
3. Friedman RJ, Rigel DS, Kopf AW. Early detection of malignant melanoma: the role of physician examination and self-examination of the skin. CA Cancer J Clin.1985;35:130-151.
4. Asierto PA, Palmieri G, Celentano E, et al. Sensitivity and specificity of epiluminescence microscopy: evaluation on a sample of 2731 excised cutaneous pigmented lesions. The Melanoma Cooperative Study. Br J Dermatol. 2000;142: 893-898.