Three‐dimensional evaluation of subclinical extension of extramammary Paget disease: visualization of the histological border and its comparison to the clinical border. (4th May 2017) - Murata, T.
Summary: Background: In extramammary Paget disease (EMPD), Paget cells are sometimes detected outside the clinical border (subclinical extension). However, the spreading pattern of Paget cells in subclinical extension remains unclear. In addition, the macroscopic appearances of lesions accompanied by subclinical extension are totally unknown. Objectives: To characterize the spreading pattern of Paget cells as well as the macroscopic appearance of lesions of EMPD with subclinical extension. Methods: Nineteen patients with primary anogenital EMPD underwent mapping biopsies and excisional surgeries; biopsy samples were then taken at the periphery of well‐demarcated lesions. Samples were transparentized and subjected to whole‐mount immunostaining with anticytokeratin 7 antibody to label Paget cells. The histological border was evaluated in three dimensions by two‐photon microscopy. The shape and location of the histological border were compared with those of the clinical border. Results: In 21 samples taken at the lesion where subclinical extension was not shown by mapping biopsy, the shape and location of the histological border were almost identical to those of the clinical border. However, two samples exhibited small foci of Paget cells outside the clinical border, showing subclinically extended satellite lesions. In the two samples taken at the lesions where subclinical extension was shown by mapping biopsy, a continuous arrangement of Paget cells extending beyond the clinical border was identified. Subclinically extended Paget cells were detected solely outside hypopigmented patches with erythema. Conclusions: In EMPD, at least two patterns of subclinical extension exist: continuous and satellite lesions. Subclinical extension might exist preferentially outside hypopigmented patches with erythema. Abstract : What's already known about this topic? Paget cells in extramammary Paget disease often spread beyond the clinical border, which is referred to as subclinical extension. The spreading pattern of the subclinically extended Paget cells remains unclear. There are no reports on the macroscopic appearances of lesions accompanied by subclinical extension. What does this study add? Three‐dimensional analysis by whole‐mount immunostaining revealed two spreading patterns of Paget cells in subclinical extension. Paget cells formed either small satellite lesions or continuous lesions forming a polygonal margin. All subclinically extended Paget cells were detected outside hypopigmented patches with erythema. Respond to this article Linked Comment: Hatta. Br J Dermatol 2017;177 :18–19