SEATTLE – Sentinel lymph node biopsy in patients with head or neck desmoplastic melanoma is positive only 6% of the time, and it doesn’t change the risk of recurrence.
Although sentinel lymph node biopsy (SLNB) is routine in more common forms of cutaneous melanoma, findings from a retrospective case-control study suggest that it’s “not really necessary” for desmoplastic melanoma (DM) of the head or neck, said lead investigator Dylan Roden, MD, of the department of otolaryngology, New York University. General surgeons have pretty much come to that conclusion for DM elsewhere on the body, but it hasn’t been shown before for neck and head lesions, he said.
Dr. Dylan Roden
DM, an invasive form of melanoma in which malignant cells are surrounded by fibrous tissue, accounts for maybe 2% of cutaneous melanomas, with half or so presenting on the head or neck. The reason SLNB is of less use than with other melanomas is that DM “doesn’t often spread through the lymphatics. It’s not that patients won’t ever have metastases, but maybe it will be through the blood. Removing a lymph node won’t necessarily” detect it, Dr. Roden said at the International Conference on Head and Neck Cancer, held by the American Head and Neck Society.
Forgoing SLNB has the added benefit of shaving an hour and a half or more off surgery, which is important since DM patients tend to be older, he added.
The NYU team matched 32 of their cases with 60 controls with more common superficial spreading or nodular melanoma of the head and neck, based on age, gender, ulceration status, and tumor stage. Mean tumor thickness in both groups was more than 4 mm.
SLNB was performed in 16 DM patients (50%) and 36 control patients (60%); it was positive in one DM patient (6.3%) versus 8 of 28 controls with reported results (28.6%).
Eleven DM patients (34%) had a recurrence, which was less frequent then in controls, where 33 patients (55%) had a recurrence (P = .05). “SNLB did not change the risk of overall or regional recurrence” in DM, Dr. Roden said.
Recurrence was more than twice as likely in control patients (odds ratio, 2.33; P = .06). Meanwhile, recurrence in DM was linked to perineural invasion (P = .02), but not ulceration status (P = .12) or mitoses (P = .40).
DM patients also had better 5-year overall survival (79% versus 62%) and disease-free survival (70% versus 42%; P for both = .06). In general, DM “has a more favorable prognosis,” Dr. Roden said.
Cases and controls were in their mid-60s, on average, and most were men. Ulceration was present in about a quarter of patients. Mitosis was more common in superficial spreading and nodular patients (92% versus 53%; P less than .001), while perineural invasion was more common in DM (40% versus 7%; P less than.001).
Although outcomes were more favorable for DM, previous studies have found a higher rate of sentinel lymph node metastases – above 20% – for DM lesions with mixed, rather than pure, pathology. The 6.3% positive SLNB rate at NYU is more in line with what’s been reported before for pure lesions. The team plans to look into the matter.
There was no outside funding for the work, and Dr. Roden had no disclosures.