BACKGROUND: The diagnosis of allergic contact dermatitis should be confirmed by skin patch tests. Distinguishing between irritant and allergic reactions is sometimes difficult.
OBJECTIVE: To analyse the in vivo morphological changes in patch test reactions compared to healthy skin, and to detect subclinical changes in doubtful reactions using optical coherence tomography (OCT). To develop an OCT-based algorithm to support patch-test grading.
METHODS: One hundred twenty-nine skin patch-test areas were scanned with OCT to evaluate the following features: architectural and vascular morphology, epidermal thickness, optical attenuation coefficient (AC), and blood flow at 0.1, 0.2, and 0.35 mm depth.
RESULTS: Most common OCT features of acute contact allergic reactions in patch tests were spongiosis with microvesicles (94.8%), macrovesicles (60.3%), and coalescing vesicles (46.6%), the latter useful in differentiating acute allergic from irritant dermatitis (P-value < .05). Objective quantitative parameters correlated well with the severity grade: epidermal thickness due to spongiosis, AC (P-value < .05) and blood flow at 0.2 and 0.35 mm (P-value < .01).
CONCLUSIONS: OCT as a noninvasive diagnostic tool, established for skin cancer diagnosis, is useful for evaluating contact allergic patch-test reactions. Not only morphological but also objective features such as blood flow and AC correlate with the reaction severity. Further studies are needed to explore the differences in irritant and allergic contact dermatitis.

Malignant melanoma is an aggressive skin cancer, which can lead to metastasis development. Vascularization enhancement is fundamental for tumor growth, worsening the prognosis. Dynamic optical coherence tomography (D-OCT) enables the in vivo evaluation of vascular patterns in skin lesions.
In vivo evaluation of the melanoma vessel morphology by means of D-OCT and correlation with Breslow index.
Retrospective analysis of histologically proven melanomas, evaluated by D-OCT at three different depths (150, 300 and 500 μm), was performed. Vessels were classified according to morphology (dots, blobs, coiled, line, curved, serpiginous), distribution (regular, irregular) and the presence/type of branches. The data were correlated with Breslow thickness.
A total of 127 melanomas were evaluated. Dotted vessels were recorded at all depths, and their irregular distribution was associated with lesions thicker than 1.0 mm (from 75% to 91%), compared with thin ones (42%) at 150 μm (P = 0.031), and from 33% to 57% vs 18% at 300 μm (P = 0.021). Serpiginous and branching vessels with bulges were predominantly seen in melanomas thicker than 2 mm at 150 μm (from 14% to 27%, P < 0.001) and 300 μm of depth (from 36% to 54%, P < 0.001).
Background noise hampered vessel detection at 500 μm. No correlation with dermoscopy/histology.
Vascular pattern evaluation at 150 and 300 μm provided data on tumor microvascular asset and its pattern of progression in accordance with Breslow thickness. Since vascular progression is theoretically linked with tumor aggressiveness, the study of vascular pattern related with melanoma metastatization capability is warranted.