SCOTTSDALE, ARIZ. — There are four aggressive skin cancers that are increasing in incidence and can be easily overlooked, warned Dr. Marc D. Brown at the annual meeting of the Noah Worcester Dermatological Society.
Lentigo Maligna
The appearance and growth of this tumor, once cavalierly called a “Hutchinson's freckle” because it resembles a dab of shoe polish, might not be noticed by patients. Even dermatologists may overlook the amelanotic variety of this in situ tumor, said Dr. Brown, director of the division of dermatologic surgery, oncology, and Mohs surgery at the University of Rochester (N.Y.).
The lesions are slow to develop and may lie camouflaged in contiguous solar lentigos or pigmented actinic keratoses, but “if you give it a long enough period of time, it will become an invasive tumor.” Dr. Brown said that 2 decades ago, he encountered lentigo malignas almost exclusively on elderly patients. Now “it's not at all unusual for me to see patients … in their 40s or 50s with their first lentigo maligna.”
Finding a surefire treatment approach to lentigo malignas remains challenging. Increasing evidence suggests the lesions often extend far beyond the 5-mm clinical margins that once were considered adequate for melanoma in situ lesions. Frozen section proponents have reported low recurrence rates, but “you really have to have an excellent lab and be very good at this.”
He said he prefers a “modified Mohs” or “slow Mohs” approach that involves sending sequential sections to a histopathologic laboratory over several days after a “very meticulous” collection of tissue around the peripheral margin. In 210 cases performed in such a manner, he reported a recurrence rate of less than 2%.
SCC in Organ Transplant Patients
The growing population of long-term survivors of organ transplantation has a 65-fold increased risk of squamous cell carcinoma. Their cancers may be multiple, fast growing, and atypical in appearance.
In one such case, a liver transplant patient he had seen 3 weeks previously presented with a 3-cm SCC at the base of his thumb. He had a positive lymph node in his axilla and developed metastatic disease in his lung within 3 months.
“We're going to be seeing more and more of these patients,” he said. The keys to management are education and vigilance. Many transplant centers fail to warn patients they should be examined frequently. When a lesion appears, have a low threshold for suspicion, he said. “It is very difficult sometimes to determine which is the bad [lesion] and which is not.”
High-risk SCCs are those that are large, multiple, deeply invasive, painful or tender, rapidly growing, recurrent, and on high-risk sites such as the scalp, ear, lip, neck, and face. Dr. Brown disclosed that he is a consultant to Graceway Pharmaceuticals LLC and Novartis. His talk, however, was not sponsored by any company.
Atypical Fibroxanthoma
This tumor is believed to be secondary to UV exposure, but unlike lentigo maligna, atypical fibroxanthoma (AFX) seems to be confined to an older population.
“It usually appears relatively nonspecifically,” he said. In general, these tumors are small, superficial, and well managed by excision with a 1-cm margin or Mohs surgery, said Dr. Brown, who was a coinvestigator in a study that found a 100% cure rate in 20 such tumors (J. Dermatol. Surg. Oncol. 1989;15:1287-92).
“If it sounds too good to be true, it's too good to be true,” he said, noting that he has now had 6 cases of metastatic AFX in his practice, and 25 have been reported in the literature.
In his experience with metastatic cases, the original lesion was small (average, 1.5 cm) and metastasis occurred early (on average, 9 months after diagnosis). The most common metastatic site was the regional lymph nodes.
Fortunately, there is a clue to potential aggressive behavior in such tumors: The immunostain LN-2 (CD74) often “lights up” in more aggressive AFX tumors, including five of the six of his cases. When he sees a worrisome clinical AFX tumor and LN-2 is strongly positive, he refers patients for adjunctive radiation therapy.
Merkel Cell Carcinoma
Merkel cell carcinoma was unknown until 1972 and then considered exceedingly rare. More than 1,000 cases have been reported in patients aged 7-75 years (although most patients are older than 65 years). Up to 15% of cases are seen in immunocompromised patients.
“I'm seeing a lot of these,” said Dr. Brown. Sometimes dome shaped and distinctly red or violaceous, they may present more subtly.
In one case, the small scalp lesion was barely pink, ill defined, and bound down to the adjacent skin. “No way I thought this was a Merkel cell,” he admitted.