Dermatopathology
Contiguous lesions in lentigo maligna

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Background

Determining the best biopsy technique for a suspected lentigo maligna can be challenging. Because complete excisional biopsy is rarely practical, the physician is left to choose an appropriate area to biopsy. Sampling error can have devastating consequences, especially if the biopsy demonstrates a pigmented lesion that was considered in the clinical differential diagnosis. The presence of a solar lentigo, pigmented actinic keratosis, or reticulated seborrheic keratosis could mislead the pathologist and clinician to the erroneous conclusion that the incisional specimen is representative of the whole, and that no lentigo maligna is present.

Objective

We have often observed the presence of a contiguous pigmented lesion adjacent to lentigo maligna. The current study was designed to determine how frequently this phenomenon occurs.

Methods

We studied Mohs debulking specimens of lentigo maligna, and broad shave biopsy specimens of pigmented lesions on heavily sun-damaged areas of the skin proven to be lentigo maligna.

Results

Contiguous pigmented lesions were present in 48% of the specimens. The most common lesion was a benign solar lentigo (30%), followed by pigmented actinic keratosis (24%).

Conclusion

Recognition of this phenomenon may prevent misdiagnosis of lentigo maligna related to sampling error.

Section snippets

Materials and methods

One hundred forty-seven lesions of LM were retrieved from the files of Brooke Army Medical Center and Geisinger Medical Center. All had histologic features diagnostic of LM (a predominantly junctional proliferation of atypical melanocytes on heavily sun-damaged skin, characterized by areas of confluent junctional growth, elongated, confluent, and irregular junctional nests, and extension along adnexal structures). Ninety-six of the specimens were consecutive debulking specimens taken before

Results

Seventy (48.0%) of the 147 cases of facial LM represented by Mohs debulking specimens and large shave biopsies on sun-damaged skin demonstrated a contiguous lesion (Table I). In 77 biopsies (52.0%), there was no evidence of a contiguous pigmented lesion, but 2 of these cases were remarkable for a lichenoid tissue reaction spanning a large portion of the specimen. Diagnostic features of LM were restricted to the remaining areas of the specimen.

Forty-four (30%) cases of LM studied demonstrated

Discussion

Pigmented lesions suspicious for LM are typically large and present in cosmetically sensitive areas. Complete excision and large incisional biopsies are impractical. Smaller biopsies, in the range of 4 mm to 6 mm are often submitted to the pathology lab.

In our study, 48% of the specimens of LM contained a contiguous pigmented lesion in at least a 6 mm segment. Fig 1, A demonstrates a portion of a LM debulking specimen. This portion is diagnostic of a benign solar lentigo. No diagnostic features

References (20)

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Funding sources: None.

Conflicts of interest: None identified.

Presented in part at the American Academy of Dermatology Meeting, New York, July 2004.

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the US Army or the Department of Defense.

Reprints not available from the authors.

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