Masson's Tumor as an Uncommon Cause of Neck Mass: A Case Presentation.

Background: Masson's tumor, commonly referred to as intravascular papillary endothelial hyperplasia (IPEH), is an uncommon growth of endothelial cells within a vessel wall that is frequently assumed to indicate an abnormal resolution of thrombosis. IPEH is most typically found in the extremities however it is rare for IPEH to appear as a neck tumor. The issue with IPEH is that it could clinically, radiologically, and pathologically imitate some malignant neoplasms such as angiosarcomas creating a diagnostic challenge.

Case Report: We describe a 21-year-old male patient who presented with right anterolateral neck swelling for 12 months. Ultrasound revealed a 9.0 × 8.0 cm well-defined echogenic hyper-vascular lesion. The contrast computed tomography (CT) scan of the neck revealed an oval, well-defined subcutaneous mass, measuring 9 × 4.5 cm, situated over and separable from the right sternocleidomastoid muscle with no significant enhancement in the post-contract study. T1-weighted and T2-weighted MRI revealed a 10 × 9 × 7 cm well-defined subcutaneous lobulated lesion superficial to the sternocleidomastoid expanding upward to the Rt. side of the cheek and below to the suprasternal region, eliciting an intermediate signal in T1 and a heterogenous bright signal (mostly fluid) in T2 with low signal foci within the mass. The decision had been reached to entirely excise the lesion surgically with safety margins for histological evaluation. Histological examination indicated thrombosed variable-sized ectatic vascular spaces with papillary formations related to the thrombus, covered with a single layer of flat endothelium, and no features suggestive of malignancy. There was no recurrence at 18 months follow-up post-surgery.

Conclusion: Masson's tumor is a benign intravascular disease with an unclear origin and no confirmed inheritance pattern. Presentation of Masson's tumor as a neck mass is incredibly uncommon. Masson's tumor lacks a distinct or distinguishing clinical and radiological appearance. Histopathologic examination is the sole definitive way for diagnosing the disease and the only tool for distinguishing it from angiosarcoma. Surgical excision is the best treatment for IPEH. Recurrence is extremely rare.