Intranodal Hemangioma as a Differential Diagnosis of Melanoma Metastasis: A Case Report of a Rare Entity.

Dear editor, Haemangiomas are common benign vascular tumours usually detected on skin, mucosal surfaces, and soft tissues. In some extremely rare cases, haemangiomas can occur within a lymph node and as such are classified as primary benign vascular tumours of the lymph nodes, along with lymphangiomas, haemangioendotheliomas, and angiomyomatous hamartomas (1-2). A study reported that the overall prevalence of benign primary vascular intranodal tumours is only 0.3% (3). Even though intranodal haemangiomas are benign and usually asymptomatic, in clinical practice it is often challenging to differentiate them from primary malignant intranodal tumours or secondary malignancies. Herein, we describe a rare case of a femoral intranodal haemangioma in a melanoma high-risk patient, which was initially diagnosed as a melanoma metastasis. This appears to be the first reported instance of an intranodal haemangioma considered as a differential diagnosis of a melanoma metastasis. A 45-year-old female patient was admitted to our Clinic in June 2021 for a regular check-up after a melanoma excision on her left upper leg three years earlier. Histologically, it was a nodular melanoma of 6.22 millimetres Breslow thickness, Clark IV level, and 5 mitoses per square millimetre. Shortly after the primary excision and due to the unfavourable histopathological parameters, a preoperative positron emission tomography/computerized tomography (PET/CT) was done in which no pathological accumulation of radiopharmaceutical was observed. In histopathological findings of subsequently performed scar reexcision and left groin sentinel lymph node biopsy (SLNB), no tumour cells were detected. Since then, the patient had regular check-ups every few months in which all clinical, ultrasound, and laboratory findings were normal. A control PET/CT for this high-risk melanoma patient was done three years later, in June 2021. In comparison with the first PET/CT, a progression in size was observed in a hyperdense lymph node in left femoral region, diameter of 15 mm, now with increased accumulation of radiopharmaceutical (Figure 1). To exclude melanoma metastasis, an ultrasound of the left femoral region was done in which a well-defined, hyperechoic lesion with increased vascularity on colour Doppler was seen. As recommended by a radiologist and due to an unclear diagnosis, a excisional biopsy of the described femoral lymph node was conducted. Histopathological analysis revealed an oval, circumscribed vascular formation within most of the lymph node tissue (Figure 2a and 2b), predominantly composed of cavernous-like blood vessels and vascular spaces filled with erythrocytes and lined with thinned endothelium (Figure 2c and 2d). The lesion was sharply demarcated from the surrounding nodal tissue. No nuclear atypia or mitotic activity was observed. The described histopathological features led to a diagnosis of a primary intranodal haemangioma. At present, four years after the primary excision of melanoma and one year after the detection of intranodal haemangioma, the patient remains disease-free. Although lymph nodes frequently show extensive vascularity associated with many different infections and diseases, the verification of a primary vascular tumour in a lymph node is a very rare occurrence (6). Apart from Kaposi's sarcoma, only few examples of such intranodal vascular tumours have been reported, of which most of them were benign haemangiomas. Haemangiomas are ubiquitous tumours that can be found on skin, mucosa, and all internal organs, and are considered as the most common benign neoplasm of the liver. Histologically, there are 4 types of intranodal haemangiomas: capillary/cavernous, lobular, cellular, and epithelioid (1,6). Intranodal haemangiomas present as asymptomatic, solitary, palpable lymph nodes or as an incidental finding. They usually affect only one lymph node and rarely cause any functional impairment. In most of the previously published cases, intranodal haemangiomas have occurred within nodes of sites draining malignant tumours, i.e., after mastectomy following breast cancer diagnosis or salpingo-oophorectomy after ovarian cancer diagnosis (2,6,7). The treatment of primary lymph node haemangiomas includes surgical resection, which is considered curative (5,8,9). The prognosis is excellent, and the recurrence rate of these tumours has not been described (6,9). In our case, surgical extirpation was performed for the purpose of excluding metastatic disease. This appears to be the first reported instance of an intranodal haemangioma considered as a differential diagnosis of a melanoma metastasis. A causative relationship between melanoma and intranodal haemangioma has not been established but it is believed that these two lesions occur independently of each other. The identification of intranodal haemangiomas is important to avoid misdiagnosis as malignant vascular tumours, such as Kaposi's sarcoma or angiosarcoma, which are more common in lymph nodes. Since Kaposi's sarcoma can initially occur in lymph nodes, without the cutaneous involvement, this distinction requires special emphasis. Moreover, intranodal haemangiomas can also be suspected as secondary malignancies, especially in patients with high-risk malignant tumours, just like our patient was, so it is of great importance to think about intranodal haemangioma as a rare differential diagnosis of a lymphogenic metastasis.