Intravascular papillary endothelial hyperplasia – known as Masson's tumor – is a rare benign entity. It was first described in 1923 by a French pathologist under the name hémangioendothéliome végétant intravasculaire.1 It is currently considered a reactive intravascular proliferation that develops either in a dilated vessel's lumen, a hematoma or a preexisting vascular lesion.2,3 No malignant degeneration has been yet reported. We present three cases of Masson's tumor of the maxillary sinus, which were all treated with endoscopic surgery and initially considered potentially malignant. A literature review of other cases found in the paranasal sinuses and nasal cavity is presented.

Masson's tumor is a rare entity that might be unfamiliar to many specialists. It mimics malignancy from a clinical, endoscopic but especially radiological, point of view. Since its first description in 1923, there have been reported cases affecting almost all parts of the human body, with only very few reports in the sinonasal area. Commonly, symptoms are not specific and related to the affected organ, with the appearance of a lump or a bleeding, rarely associated with pain. The radiological assessment and the biopsies often suggest malignancy. According to one of the largest series reported, this tumor is frequently subcutaneous and dermal with a predilection for the head and neck, digital and trunk regions.2 Cases were also described in the liver, the orbit, intramuscularly, in the oral cavity and intracranially. To the best of our knowledge, only 10 cases, prior to the our reported ones, involved the paranasal sinuses or nasal cavity.3–12 A review of the existing literature on this subject is summarized in Table 1. The men versus women ratio is 1.6:1 and the mean age of presentation is 41±16 years old. The symptoms are those of any sinonasal pathology and do not show specificity.

Clinico-histological correlation is important when dealing with this lesion. In our experience, the higher the clinical suspicion, the higher the chances to match proper histological diagnosis. It remains speculation, but it could be that Masson's tumor in the paranasal sinuses is perhaps less rare than reported, due to a low clinical suspicion and a lack of communication between the surgeon and the pathologist. A similar phenomenon has been observed recently with hamartomas of the olfactory clefs (REAH),13 where the mention of the entity in the clinical differential diagnosis addressed to the pathologist increases the number of cases found.

The endoscopic aspect during resection must also prompt the surgeon to specifically request the search for intravascular papillary endothelial hyperplasia. In the three cases presented here, the clinical appearance was avascular, without the accompanying expected bleeding. The mass appeared to be poorly vascularized and easy to resect. It was further surprising for the surgeon that the masses lacked a real attachment or insertion point to an intact mucosa, similar to what is observed with removal of a fungus ball.

Radiologically, the three cases presented similarly with a heterogeneous mass suggesting a malignant or at least a solid and tissue process. The differential diagnosis for all three cases were inflammatory polyp, inverted papilloma, lymphoma, adenocarcinoma, squamous cell carcinoma or metastasis. It is difficult on the basis of these three cases to conclude to what extent radiology can suspect this rare specific lesion. On the other hand, it is clear that MRI adds a preoperative value in cases of unilateral opacity discovered on CT. It is also striking to see the similarity on magnetic resonance imaging of all three lesions presented and the cases reported in the literature, to the point where we raise the question if the diagnosis could not already be suspected in the basis of MRI.

Histologically, Masson's tumor must be differentiated from angiosarcoma.14 Histological analysis showed an organized hematoma associated with non-atypical intraluminal endothelial proliferation, characteristic of intravascular papillary endothelial hyperplasia. A correct diagnosis will allow adequate treatment which consists of a complete resection, thus avoiding overtreatment. In our modest series, two patients had a concomitant oncological condition, which raises the question of a simple coincidence or of a potential cofactor promoting the formation of Masson's tumor. The literature, based on small number of cases reported, cannot answer this question.

Three new cases of intravascular papillary endothelial hyperplasia of the maxillary sinus are presented. The endoscopical, radiological and pathological characteristics are discussed. These are the 6th, 7th and 8th cases of maxillary sinus involvement reported in the literature. Due to its clinical and radiological presentation, Masson's tumor is often mistaken for a malignant disease and the histology analysis only can confirm the benign diagnosis. The definitive treatment is the complete resection of the lesion.

The authors declare no conflicts of interest.