Differentiating between benign skin lesions and melanoma to identify cancers with unusual presentation can be tricky, and it typically makes sense for dermatologists and pathologists to work together, specialists reported at the World Congress of Dermatology 2019.
“Dermoscopy can help physicians improve their diagnoses, but it cannot be relied on alone,” said Rino Cerio, MD, from Royal London Hospital. “Close clinical and pathologic correlation is essential.” It will lead to better outcomes for the patient and valuable opportunities for specialists to learn from each other,” he explained.
“What we try to do, both clinically and pathologically, is separate the sheep from the wolves, the saints from the demons,” Cerio said. “But “nature is not always like that” and there can be a lot of ambiguity,” he added.
Cerio described the case of a 61-year-old man who was referred to his institution by a general practitioner after a punch biopsy. The doctors suspected a thrombosed hemangioma. Histology showed that it was a melanoma.
“Immunohistological chemistry confirmed that these cells were indeed positive for melanoma,” he reported. “This was totally missed clinically.”
Another potential misdiagnosis involved a woman with eczema around the nipple of one breast. She arrived as an urgent referral from the breast clinic. When a test for Paget’s disease came back negative, doctors performed a biopsy.
It turned out that because the patient’s breasts were not the same size, she developed contact dermatitis when the nipple of her larger breast rubbed against the seam of her bra.
“Beware the iceberg effect,” Cerio cautioned. “If you think it’s a tumor, you need to know what’s underneath it.” Juliana Williams, RPA-C, a physician assistant at the West Derm Center in Bronx, New York, said she attended the session because she performs biopsies and wants to know more about tumor pathology.
She said she agrees that it would be helpful to work more closely with pathologists. “As clinicians, we don’t have much opportunity to see the dermatopathology slides.”
“Amelanotic melanoma can be particularly difficult to diagnose,” Cerio pointed out.
This is “one of the great masqueraders” and can be a “diagnostic challenge,” explained Sophie Paget, a dermatology resident at Royal London Hospital, who gave a presentation on how to identify these lesions. “They get missed because they don’t look like melanomas; they are not brown or black.
She looked at 24 cases of amelanotic melanoma from three large East London hospitals. Only 17 had been biopsied to rule out amelanotic melanoma. The others were thought to be squamous cell carcinoma, viral warts, or keratosis.
Amelanotic melanoma occurs equally in men and women with fair skin, usually on the limbs, Paget said. Some clinical signs to watch out for include the long-time presence of the lesion.
The mean time between the patient noticing the lesion and seeking care is 2 years, but it can range from 1.5 months to 5 years. “The tumors tend to be thick, but can mimic a range of benign lesions,” she added.
Dotted and irregular linear vessels and amorphous pink, blue, or pigmented edges can be revealed on dermoscopy, but that is of limited use if the lesion is bleeding, she pointed out.
Dermatologists should have a low threshold for ordering a full thickness biopsy for suspected amelanotic melanoma, said Paget, who offered the same advice given by Cerio: “When in doubt, cut it out.”