Intravascular Papillary Endothelial Hyperplasia of the Upper Limb Mimicking a Vascular Neoplasm: Case Report and Literature Review.

INTRODUCTION: Intravascular papillary endothelial hyperplasia (IPEH), also known as Masson's tumour, is a rare benign vascular lesion caused by reactive endothelial proliferation within vascular spaces. Despite its benign nature, IPEH may clinically and radiologically mimic malignant vascular tumours, particularly when arising in the upper extremity, posing a diagnostic challenge. REPORT: A 38 year old woman presented with a slowly enlarging subcutaneous nodule in the left antecubital fossa, with no history of trauma. Ultrasonography revealed a well defined solid mass with heterogeneous echotexture and suspected vascular communication. Magnetic resonance angiography demonstrated a solid lesion in continuity with the ulnar artery, with segmental arterial interruption and distal reconstitution, raising concern for a vascular neoplasm. An en bloc surgical resection was performed, including ligation of the involved ulnar vessels, without compromising distal perfusion. Histopathological examination showed papillary endothelial proliferation confined within a venous type vessel, without cytological atypia or necrosis, confirming primary IPEH. DISCUSSION: To contextualise this case, a review of the literature was conducted, identifying 103 reported cases of IPEH involving the upper extremities. Lesions most frequently affected the fingers, followed by the forearm and elbow, with a slight female predominance and a mean age in the fourth decade of life. Primary (type I) IPEH accounted for nearly all cases. Complete surgical excision was associated with excellent outcomes and low recurrence rates. Awareness of IPEH is important, and it should be included in the differential diagnosis of vascular tumours to avoid unnecessarily aggressive oncological resections, although complete surgical excision remains the standard initial management.