Dermatopathology
In vivo confocal scanning laser microscopy of benign lentigines: Comparison to conventional histology and in vivo characteristics of lentigo maligna

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Background

An important challenge facing clinicians is recognizing and distinguishing benign pigmented lesions from cutaneous melanoma. Lentigines are a type of benign pigmented lesion that can resemble melanoma. Physician diagnostic accuracy is less than perfect, prompting research into noninvasive technology such as reflectance mode in vivo confocal scanning laser microscopy (CSLM).

Objectives

Our aims were twofold: to describe the in vivo characteristics of benign lentigines with reflectance CSLM and to compare them with histopathology; and to contrast the in vivo CSLM differences of lentigines, lentigo maligna, and lentigo maligna melanomas.

Methods

Patients with a suspect pigmented lesion were prospectively recruited to undergo CSLM before biopsy. Lentigo simplex, solar lentigo, or malignant melanoma, lentigo maligna type, were included in the study. Images were qualitatively described and compared with histopathologic findings.

Results

Ten patients, whose lesions included 6 lentigines and 4 lentigo malignas, were examined with CSLM. Distinct architectural and cytologic features were noted in benign lentigines compared with melanomas. The most striking finding in lentigines was observed at the dermoepidermal junction. In all cases of lentigines there was an increase in the density of dermal papillae surrounded by a bright monomorphic layer of cells. Distinct patterns were noted, as these papillae assumed irregular geometric shapes or formed papillary projections with a rim of bright, highly refractile, monomorphic, and cytologically benign-appearing cells. These findings were absent in all of the melanomas studied. Lentigines had an absence of atypical melanocytes, whereas the melanomas had bright, atypical, polymorphous cells present in a pagetoid pattern with coarse, branching dendrites observed throughout the epidermis.

Limitations

This is a descriptive pilot study involving a limited number of patients.

Conclusion

Unique CSLM characteristics of lentigines were found that have not been previously described, facilitating rapid in vivo discrimination from malignant melanoma. This descriptive study supports the further examination of CSLM features of lentigines to aid in the diagnosis of melanoma and discrimination from benign lesions.

Section snippets

Patients

Patients were recruited prospectively during the period February 2002 through July 2005 for an ongoing Institutional Ethics Committee–approved study of CSLM at our pigmented lesion clinic at the Queen Elizabeth II Health Sciences Centre, Dalhousie University. Patients gave oral and written consent for the study. All patients were scheduled for biopsy of their lesion due to clinical suspicion of malignancy because of clinical appearance or change in the lesion.

Results

Ten patients were enrolled in this study, with lesions including 1 lentigo simplex, 1 lentigo simplex/evolving junctional nevus (“jentigo”), 4 solar lentigines, and 4 LMs. Demographic information, lesion characteristics, and pathologic diagnosis are listed in Table I. Patients' ages ranged from 39 to 70 years (mean, 53 years) and included 6 men and 4 women.

Discussion

Reflectance in vivo confocal microscopy has been recently investigated in dermatology as a tool with the potential to aid in clinical diagnosis of benign and malignant skin lesions. The nondestructive nature of optical “sectioning” avoids artifacts due to tissue processing and provides a high-resolution, instantaneous examination of the skin in its natural state, so dynamic processes and architectural and cellular features of the skin can be visualized.10, 17 Lentigines are particularly suited

References (31)

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    With dermatoscopy, SL classically demonstrates irregular, sharply demarcated lateral edges resembling “moth-eaten borders” (Figure 1A), homogenous light brown featureless pigmentation, areas of a symmetrical pigment network, and fingerprint-like areas composed of parallel fine lines resembling dermatoglyphics.2 RCM of SL demonstrates normal architecture at the level of the mid-epidermis with preservation of the typical honeycomb and cobblestone epidermal patterns, denoting a lack of atypia within keratinocytes.3-5 At the level of the dermo-epidermal junction (DEJ), the dermal papillae are ovoid to annular to polycyclic in shape and are surrounded by a rim of hyperrefractile uniform basal keratinocytes (known as “edged papillae” forming the ring pattern).3,4

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    The regular honeycomb pattern correlates to a lack of keratinocytic atypia on histopathology. Solar lentigo on RCM is distinct at the level of the dermoepidermal junction (DEJ), demonstrating an increased density of “edged papillae”—dermal papillae rimmed by bright uniform basal cells.2 This refractile layer of cells correlates with a cross-sectional view of rete ridges that are lined by pigmented basal keratinocytes.2

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Supported by grants from Canadian Institute for Health Research/Faculty of Medicine, Dalhousie University Summer Studentship; Nova Scotia Health Research Foundation, and the Canadian Dermatology Foundation.

Conflicts of interest: None identified.

Study presented at the 14th Congress of the European Academy of Dermatology and Venereology, London, United Kingdom, Oct 12-16, 2005.

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