From the Journals

Topical imiquimod helps clear blurred lines in lentigo maligna excision



The use of neoadjuvant, topical imiquimod 5% cream is associated with a decrease in melanocyte density counts (MDC) when treating lentigo maligna (LM), according to a study from the University of Utah.

Lentigo maligna is a subtype of melanoma in situ, usually occurring in the head and neck regions, the researchers said.

“Neoadjuvant topical imiquimod 5% cream applied 5 times weekly for 8 weeks was associated with decreased MDCs in LM treatment sites compared with the MDCs of negative control sites,” wrote Shadai Flores of the University of Utah, Salt Lake City, and her colleagues.

Previously, the ability to distinguish between the surgical border and surrounding background melanocytic hyperplasia was uncertain. Because of this uncertainty, LM removal required an average margin of 7.2 mm. Another study showed that topical imiquimod 5% cream enabled the removal of most LM tumors with 2-mm margins. This study “sought to evaluate MDCs in imiquimod-treated LM and negative control biopsy specimens to determine if there was a measurable difference in melanocyte density,” the researchers wrote in a research letter published in JAMA Dermatology.

The study prospectively followed 52 cases of LM treated with imiquimod 5% topical cream 5 days per week for 8 weeks followed by conservative staged excisions with 2-mm margins. Treatment with imiquimod 5% of LM was followed by a 2- to 4-month recuperation period before surgery could be performed. All patients in the study were treated by one Mohs surgeon at the Huntsman Cancer Institute at the university.

To establish an MDC baseline, a 10-mm long fusiform biopsy was taken as a negative control. The negative control sample site and the LM site were separated by approximately 6 cm, found on the same side of the body, and showed similar color changes. After a negative control was taken, an LM lesion was resected and subsequently quadrisected. The MDCs then were concurrently counted by the researchers and compared with the negative controls.

Of the 52 LM specimens, 44 (85%) exhibited decreases in MDCs, compared with the negative controls. The median MDC from post–imiquimod-treated sites was 14.4, with a range of 0.5-26.6. This showed marked improvement over the negative controls, which had a median MDC of 20.0 (range of 9.0-36.7). A 2-tailed paired t test revealed that the results displayed statistical significance (P less than .001). Residual LM was seen in the central areas of 9 (17%) specimens, but 43 (83%) had no indication of residual LM.

“The decreased melanocytic hyperplasia in imiquimod-treated sites reduced ambiguity in making a distinction between the border of the excised LM and background melanocytic hyperplasia,” noted Ms. Flores and her colleagues.

The authors had no conflicts of interest.

SOURCE: Flores S et al. JAMA Dermatol. 2018 Feb 16. doi: 10.1001/jamadermatol.2017.5632.

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