## 4 Discussion
Additionally, this introduces a new parameter and methodology that aims to enhance the understanding of tumor growth and progression, potentially leading to more effective therapeutic strategies and interventions. [PERSON] et al. demonstrated in 2022 that conventional D-OCT can be used effectively for therapy monitoring in inflammatory dermatoses, such as psoriasis and atopic dermatitis, during systemic treatment. In their study, changes were observed in vascular density, plexus depth, vessel diameter, and vessel count [37]. Preliminary follow-up investigations in our study on therapy monitoring, both under local and systemic immunotherapy, show promising results regarding vascular changes in various skin tumors. In 2002, [PERSON] et al. first described corkscrew vessels in the dermoscopy of melanoma metastases, which can be clearly identified in the dermoscopic image shown in Figure 3[38]. The metastasis of malignant melanoma has been the subject of various research studies focusing on D-OCT imaging; however, the blood vessels associated with these melanomas have never been specifically investigated using this imaging technique [39; 40]. However, until now, it was not possible to visualize these vessels in 3D. Using the deepLiveTM LC-OCT device in combination with advanced image processing tools, such as the Simple Neurite Tracer (SNT) plugin in ImageJ, it is now possible to visualize and analyze these vessels in vivo, as demonstrated in Figure 3. The fact that the corkscrew vessel twists are primarily due to their extension across multiple layers can only be conclusively proven through 3D imaging. The linear-irregular vessels described by [PERSON] et al. were also successfully visualized using 3D segmentation in Figure 4[41]. This is particularly important in cases of vascular polymorphism in squamous cell carcinoma (SCC), where elongated, non-homogeneous vessels coexist with dotted, linear-irregular, or glomerular vessels. A 3D representation can aid in illustrating the features of these specific vessels, as described in the literature, since in 2D imaging, vessels are only partially displayed, preventing an accurate visualization of their spatial relationships [42; 43]. [PERSON] et al. have previously described the vessels of SCC using D-OCT. Their study revealed various irregular forms and patterns of the vessels, as well as changes in vessel diameters. The images also displayed multiple diverse and atypical vascular forms, such as dots, blobs, and curves. However, these could not be directly correlated, as the technique only allowed for visualization in a single plane. The assessment of these vessels was useful in determining the invasiveness of the carcinoma, as disordered and irregular vessels are indicative of malignancy [18]. In Figure 5, hairpin vessels were already visible in dermoscopy, and these were subsequently identified in the dermis using LC-OCT. According to the literature, this vascular morphology is observed in both melanocytic and non-melanocytic tumors, and occasionally even in benign skin lesions [44; 45]. In Figure 5, these vessels were depicted in direct association with the nodular tumor nests of a nodular BCC, a finding previously described by [PERSON] et al. using RCM [46]. Notably, thick, large-caliber vessels, as seen in our case, are well-documented in the literature. [PERSON] et al. describe thick, branching arborizing vessels that taper towards the periphery, while [PERSON] et al. reported hairpin vessels in 66.7% of cases involving aggressive BCCs of the lower extremities [46; 47]. This is consistent with our findings, as the patient's pigmented nodular BCC was located on the extensor surface of the lower leg. [PERSON] et al. also described the blood vessels surrounding tumor nests in BCCs. Their studies report the presence of both very thick and very thin vessels. Similarly, our LC-OCT 3D reconstruction, as previously described, also reveals both very thick and very thin vessels.