Consistency and distribution of reflectance confocal microscopy features for diagnosis of cutaneous T cell lymphoma

Abstract

Reflectance confocal microscopy (RCM) represents a noninvasive imaging technique that has previously been used for characterization of mycosis fungoides (MF) in a pilot study. We aimed to test the applicability of RCM for diagnosis and differential diagnosis of MF in a clinical study. A total of 39 test sites of 15 patients with a biopsy-proven diagnosis of either MF, parapsoriasis, Sézary syndrome, or lymphomatoid papulosis were analyzed for presence and absence of RCM features of MF. Cochran and Chi(2) analysis were applied to test the concordance between investigators and the distribution of RCM features, respectively. For selected parameters, the Cochran analysis showed good concordance between investigators. Inter-observer reproducibility was highest for junctional atypical lymphocytes, architectural disarray, and spongiosis. Similarly, Chi(2) analysis demonstrated that selected features were present at particularly high frequency in individual skin diseases, with values ranging from 73% to 100% of all examined cases.

Fig. 1

Panels (a) and (b) illustrate the presence of atypical lymphocytes in MF. Panel (a)  demonstrates the presence of small to medium-sized bright round cells (yellow arrowheads) in between keratinocytes, which corresponds to exocytosis of lymphocytes on histopathologic examination. Panel (b) shows multiple bright round cells of varying morphology (yellow arrowheads) at the (DEJ within the dermal papillae (white dashed circle). Panel (c) illustrates normal honeycomb pattern of the granular/spinous layer, and (d) shows the DEJ morphology with dermal papillae (white dashed circle) in absence of any inflammatory infiltrate.

Fig. 2

Panels (a) and (b) show architectural disarray appearing in lesions of MF. Panel (a) illustrates the disruption of the normal regular honeycomb pattern of the granular-spinous layer, displaying areas of dark reflectance in the center and blurred intercellular connection of the keratinocytes (white asterisk). Panel (b) shows RCM findings at the DEJ with the presence of inflammatory cells and aberrant morphology compared to normal skin as shown in panels (c) and (d).

Fig. 3

Panels (a) and (b)  show representative images of MF illustrating RCM features of spongiosis. Panel (a) was obtained at the granular-spinous layer, demonstrating dark areas of low refractility (asterisk), in which the delineation of the single cells and the overall honeycomb appearance of the epidermis is disrupted. Panel (b) shows a similar aspect (asterisk); furthermore, single keratinocytes with prominence of bright cytoplasm are noted (red arrowheads). Panel (c) shows normal granular layer of the epidermis with skin folds (asterisk) and, (d) illustrates typical honeycomb pattern of the spinous cell layer.

Fig. 4

Panels (a) and (b) demonstrate RCM feature of hyporefractile papillae. Images were obtained at the DEJ and illustrate the absence of the bright rim of pigmented basal keratinocytes and melanocytes that is usually seen around the dermal papillae. Panels (c) and (d) illustrate normal, so-called edged papillae, which characteristically display a bright rim of small bright round cells around the dermal papillae.

Fig. 5

Panels (a) and (b) show representative images of Pautrier’s MF in mycosis fungoides, illustrating multiple, well-circumscribed, vesicle-like areas of varying size and dark reflectance (asterisk) at the granular-spinous layers. Within these nonrefractile areas, remaining keratinocytes can be visualized (red arrowheads). These keratinocytes focally still show adherence by intercellular connections, but intercellular spaces are widely enlarged and the epidermal structure is disrupted. Furthermore, small bright cells representing inflammatory cells are noted (yellow arrowheads). Panels (c) and (d) demonstrate corresponding RCM findings of normal skin at the granular-spinous layers with typical honeycomb pattern. Areas that appear slightly darker than the surrounding epidermis represent areas with underlying dermal papillae.