Trauma leading to hemorrhage mimics ALM
The differential diagnosis includes both melanocytic lesions and non-melanocytic lesions. Benign nevi or dysplastic nevi are included in the first category. Among non-melanocytic lesions, trauma leading to hemorrhage may mimic ALM.2 ALM has also been misdiagnosed as pyogenic granuloma, ischemic ulceration, wart, a foreign body, callus, a nonhealing wound, or other benign skin lesions such as seborrheic keratosis.2,8,9
Amelanotic lesions are particularly misleading on the foot, as they may be frequently misdiagnosed as hyperkeratotic benign lesions.8 Bleeding, itching, satellite lesions, and sudden growth, however, should raise your suspicion of melanoma.10
Excision is best, plus sentinel node mapping
The most effective treatment for ALM is excision—either conservatively or with wide margins—along with sentinel lymph node mapping.11 Systemic chemotherapy is more palliative than curative, as it has not been shown to improve the number of recurrences.2 Patients require lifelong regular full body skin exams with early biopsy of any suspicious skin lesions.9
The prognosis of ALM is poorer than other subtypes of melanoma, mainly because of delayed diagnosis.2,9 The single most important and accurate prognostic factor is the depth of invasion of the tumor as measured by Breslow thickness.10
Other factors that are predictive of a poorer prognosis in ALM patients are male sex and amelanosis.12 It’s important to recognize that the palms, soles, and nails may be sites for melanoma—despite the lack of direct sun exposure.
Our patient required amputation
Our patient’s toe was amputated and the melanoma had a Breslow thickness of 7 mm. Sentinel lymph node biopsy was negative. Our patient received adjuvant chemotherapy with interferon alfa-2B and was followed by oncology.
Where are you most likely to spot melanoma?
If you said the face or the arms, you’d be wrong. Given that increased sun exposure and a history of multiple sunburns are recognized as important risk factors for melanoma, it’s easy to assume that the most common sites for melanoma would be exposed areas of the body, such as the face and arms.
Interestingly, though, superficial spreading malignant melanoma—the most common type of malignant melanoma13—is most often found on the legs in women and on the back in men.3,10 One theory is that repeated intense exposure to sunlight may be a more important risk factor than continuous sun exposure.14,15
Correspondence
Rajani Katta, MD, 6620 Main Street, Suite 1425, Houston, TX 77030.