Line‐Field Confocal Optical Coherence Tomography (LC‐OCT) of Masson's Tumor

Masson's tumor, also known as intravascular papillary endothelial hyperplasia (IPEH), Masson hemangioma or Masson pseudoangiosarcoma, is a rare benign vascular tumor caused by the presence of an organizing thrombus and associated hyperplastic endothelial cell proliferation within the lumen of a blood vessel [1]. It typically presents as a painless, tender, or non-tender, purple nodular lesion varying in size from 0.2 to 5 cm and can affect skin and soft tissues of internal organs. More common among adults, it was also described in children and in the elderly, with a slight predilection for the female sex [1]. As described by Hashimoto et al. in a clinicopathologic study of 91 cases, IPEH can be classified as “pure” if it arises within a normal capillary, “mixed” if it appears within a pre-existing vascular neoplasm such as a haemangioma, lymphangioma, or pyogenic granuloma or “unclassifiable” to identify rare extravascular forms that may arise in a hematoma [1, 2]. Dermoscopy doesn't provide specific features for the diagnosis of these lesions, and it is poorly reported in literature, therefore, the histological examination remains mandatory for a correct diagnosis of the lesion [3]. Line-field confocal optical coherence tomography (LC-OCT, DAMAE Medical, Paris, France) is an innovative technique that enables real-time imaging of the skin at a quasi-histologic resolution. In recent years, “virtual biopsies” provided by LC-OCT proved to increase the diagnostic accuracy for skin cancers as well as for cutaneous vascular lesions and melanoma [4-7]. Herein we describe the case of a 67-year-old woman with a history of cutaneous melanoma of the scalp and in transit metastases (stage III AJCC) who was undergoing immunotherapy treatment with Nivolumab 480 mg administered intravenously every 4 weeks at our clinic. In the last 3 months, the patient reported the rapid growth of a purplish colored nodular lesion located in the right iliac fossa (Figure 1A,B) which was documented as suspicious for subcutaneous metastases from melanoma in her most recent total-body CT examination. On clinical examination, the lesion appeared purplish with co-presence of whitish areas, soft to the touch, and measured 1.5 cm × 1.2 cm in size. Dermoscopy revealed nonspecific findings such as purplish and white structureless areas with indistinct borders (Figure 1C). Based on clinical and dermoscopic criteria, the differential diagnosis included both benign skin lesions such as haemangiomas, pyogenic granulomas, lymphangiomas, and malignant skin lesions such as angiosarcomas, basal cell carcinomas, melanomas, and skin metastases. In a recent paper on the dermoscopic patterns of skin metastases, it was found that blue structureless areas are the prevalent pattern in melanoma metastases, with brown and white structureless areas also being prevalent [8]. 3D cube LC-OCT sections revealed the presence of vascular lacunae in the dermis and the absence of nests of atypical melanocytes (Figure 2A,B). A targeted biopsy at a site selected via LC-OCT, confirmed the diagnosis of a vascular lesion, specifically Masson's tumor. The pathological specimen revealed thin-walled dermal vascular structures with cyst-like dilations containing hemorrhagic content and fibrinoid material (Figure 2C). Multiple endoluminal papillary formations were present, lined by a single layer of endothelial cells without cytological atypia or pleomorphism. In conclusion, LC-OCT, through high resolution and penetration, could be a valuable additional tool in the diagnosis of this rare tumor. LC-OCT managed to quickly and non-invasively reveal the vascular nature of the lesion, with the advantage of reducing patient anxiety, which has a big impact on the oncological patient. Therefore, LCOCT offering high-resolution imaging may improve diagnostic accuracy and patient care. Gerardo Palmisano: conceptualization, methodology, validation, writing – review and editing, project administration. Azzurra Iacoangeli: conceptualization, writing – original draft. Daniele Omar Traini: methodology, data curation, visualization, writing – review and editing, project administration. Enrico Bocchino: visualization, project administration. Francesco Brunetti: data curation. Ketty Peris: supervision, writing – review and editing. Alessandro Di Stefani: methodology, validation, supervision. The authors received no specific funding for this work. All patients in this manuscript have given written informed consent for participation in the study and the use of their de-identified, anonymized, aggregated data and their case details (including photographs) for publication. Ethical Approval: not applicable. The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author.