Langerhans cells and melanocytes share similar morphologic features under in vivo reflectance confocal microscopy: A?challenge for melanoma diagnosis

Abstract

Background Intraepidermal Langerhans cells (ILC) are difficult to differentiate from melanocytes under reflectance confocal microscopy (RCM) and their presence may simulate pagetoid spread of melanocytes on RCM images. Objective To correlate bright round and dendritic cells in a pagetoid pattern identified on RCM with findings of conventional histopathology and immunohistochemistry for lesions that were falsely diagnosed as melanoma by RCM. Methods This retrospective study included histopathologically proven nevi, imaged by RCM, which displayed bright cells in a pagetoid pattern (BCPP) under RCM, resulting in the incorrect RCM diagnosis of melanoma. Morphological comparisons were histopathologically proven melanomas displaying BCPP on RCM and biopsy-proven nevi without such cells on RCM. Results We identified 24 nevi that were falsely diagnosed as melanoma by RCM due to the presence of BCPP. These pagetoid cells on RCM corresponded on histopathology to ILC with a high density in 23 of the 24 nevi (95%) and to melanocytes in 7 of the 24 nevi (29%). Among 6 melanomas displaying BCPP on RCM, ILC with high density were observed histopathologically in 5 of the 6 cases (83%) and pagetoid melanocytes were seen in all 6 cases (100%). Limitations The results cannot be generalized to clinically banal-appearing nevi. Conclusions Although the finding of BCPP is a useful RCM feature for the diagnosis of melanoma it does not always imply the presence of pagetoid melanocytes but may at times, represent ILC.

Dermoscopic and Reflectance Confocal Microscopy Findings in Extra-genital HPV16-associated Pigmented Squamous Cell Carcinoma in situ

“…In the present case series, the RCM features of atypical and sometimes disarranged honeycomb pattern at the spinous-granular layers and small closely-set rings of bright basal cells around the dermal papillae were indeed commensurate with the diagnosis of pigmented SCCIS (12). Of note, RCM showed the presence of numerous bright dendritic cells in the supra-basal epidermis; using IHC staining for CD1A and Melan-A, these dendritic cells proved to be Langerhans cells and not melanocytes in Pagetoid spread (13). Similarly, Moscarella et al (14) described intraepidermal proliferation of Langerhans cells in pigmented actinic keratosis, represented by dendritic cells seen on RCM.…”

Differential diagnosis of nonmelanoma pigmented skin lesions based on harmonic generation microscopy

“…40,41 A recent publication has demonstrated that Langerhans cells and melanocytes share similar morphologic features as bright dendritic cells under in vivo reflectance confocal microscopy. 42 Our preliminary immunohistochemical studies also revealed CD1a-or HMB45-positive dendritic cells in the BCC nests.…”

Differentiating intratumoral melanocytes from Langerhans cells in nonmelanocytic pigmented skin tumorsin vivoby label-free third-harmonic generation microscopy

“…Under RCM, dendritic bright cells in a pagetoid pattern (BCPP) could be observed in both benign melanocytic nevi and melanoma. 25 These bright pagetoid cells most frequently were LCs in nevi but melanocytes in melanomas, and there were no reproducible differences in morphology of BCPP between melanocytic nevi and melanomas; 25 although, Gerger et al 14 showed that dendrite-like structures with a complex branching pattern were frequently seen in melanoma and less frequently in benign nevi. In comparison to our study, the THG-enhanced dendritic-cell-like signals were specifically recognized as melanocytes, yet the dendritic BCPP shown by RCM could be melanocytes or LCs.…”

“…In comparison to our study, the THG-enhanced dendritic-cell-like signals were specifically recognized as melanocytes, yet the dendritic BCPP shown by RCM could be melanocytes or LCs. 25 Therefore, THG microscopy may have a significant role to increase diagnostic specificity of BCPP for melanoma diagnosis.…”

“…23 Intratumoral melanocytes could also be identified in nonmelanocytic tumors such as pigmented BCC by in vivo RCM. 11,24,25 However, it is hard to differentiate melanocytes from intraepidermal Langerhans cells (LCs), since both are cells with prominent dendritic processes and share similar morphology under RCM. 11,25,26 Thus an improved in vivo imaging modality is needed for making a clear differentiation between melanocytes and LCs.…”