A 43-year-old man was referred to our dermatologic unit due to the recent onset of pain, triggered by cold exposure, on a skin lesion located on the chest. This lesion had been present for approximately 20 years and had progressively increased in size over time, reaching a current diameter of 1 cm (Figure 1). On clinical evaluation, a firm smooth bluish nodule, mobile over the deep planes, was observed. Dermoscopically, the lesion exhibited a central area of structureless, homogeneous bluish pigmentation on a faint light-brown pseudonetwork background. No vascular structures or shiny white structures were observed. A peripheral collarette and vascular lobules were absent. The nodule was excised with clear margins, resulting in complete resolution of symptoms. Histological examination revealed a well-circumscribed, dermal proliferation of ovoid spindle-shaped cells arranged concentrically around vessels. Cytologic atypia and mitoses were absent. Immunohistochemical stains revealed diffuse staining of the lesional cells with α-smooth muscle actin (SMA) and h-caldesmon, focal staining with calponin and negative staining with desmin, human herpesvirus 8 (HHV-8), and HMB-45. A diagnosis of myopericytoma was established. No recurrence was observed during 6 months of follow-up. Myopericytoma is a rare, slow-growing tumor that arises from the proliferation of perivascular myoid cells. It is typically reported as a single nodule on the extremities, but it can occasionally affect head and neck regions or other sites 1. Although most cases of myopericytoma are asymptomatic, painful cases have been reported 1. These tumors are considered to be acquired, probably associated with local trauma, although the exact etiology is unknown 2. Myopericytoma has a diffuse multinodular variant, known as myopericytomatosis 1. Although the tumor is predominantly benign, a malignant variant has been reported. As a result, biopsy should be performed in all cases. Histologically, myopericytomas are characterized by a well-circumscribed, non-encapsulated, concentric proliferation of round-to-spindle-shaped perivascular myoid cells 3. Different dermoscopic presentations have been previously described, including unfocused arborizing vessels, structureless light-brown areas, and shiny white streaks 2, 4. Other patterns include homogeneous white-red areas surrounded by a whitish collarette and classic features of pyogenic granuloma 2, or multiple red lobules resembling vascular lesions 1. To our knowledge, myopericytoma has rarely been described as a predominantly homogeneous bluish nodule, and only in the subungual location 3. This uncommon presentation expands the well-established category of blue-colored skin lesions, which have long represented a diagnostic challenge. In the present case, the main differential diagnoses included melanocytic lesions such as common blue nevus and nodular melanoma, including the possibility of a cutaneous melanoma metastasis 5. Although homogeneous blue pigmentation is classically associated with blue nevus, the absence of a long-standing, stable history precluded a confident benign diagnosis 5. Nodular melanoma was also considered, as it may present as a purely structureless blue lesion lacking additional melanoma-specific dermoscopic criteria 5. Among non-melanocytic lesions, vascular and perivascular tumors were a key consideration. Dermoscopy did not reveal well-demarcated lacunar structures or other specific vascular patterns, arguing against hemangioma or vascular malformations 5. A glomus tumor represented a relevant differential diagnosis given the presence of pain and cold sensitivity, which are characteristic clinical features of this entity 5. In addition, a dermatofibroma—particularly the hemosiderotic variant—was considered, as it may present as a homogeneous blue nodule due to dermal hemosiderin deposition 5. This case highlights that myopericytoma can present as a predominantly homogeneous bluish nodule, a rare and previously underreported dermoscopic pattern. Awareness of this presentation may aid clinicians in including myopericytoma in the differential diagnosis of blue nodular lesions and reinforce the role of histopathology for definitive diagnosis. This work was supported by Fondazione IRCCS Ca′ Granda Ospedale Maggiore Policlinico of Milan/Italian Ministry of Health (RC2023). This retrospective review of patient data did not require ethical approval in accordance with local guidelines. The patient in this manuscript has given written informed consent to publication of their case details. The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.
Valtellini et al. (Thu,) studied this question.