A case report: Masson’s tumor (intravascular papillary endothelial hyperplasia) of the abdominal cavity

Introduction

Intravascular papillary endothelial hyperplasia (IPEH), also known as Masson’s tumor, is a rare benign vascular lesion first described by the French pathologist Masson in 1923 (1). In 1932, Henschen proposed that Masson’s tumor is a reactive process rather than a neoplastic one (2). The primary pathological change in IPEH involves thrombosis within blood vessels, followed by endothelial cell proliferation and the formation of papillary structures, which exhibit benign biological behavior. IPEH can occur in any part of the body, but it is more commonly found in the head, neck, and limbs (3), typically presenting as a slowly growing, painless nodule (4,5). Intra-abdominal IPEH is exceedingly rare, with only isolated cases reported. Epidemiologically, IPEH accounts for approximately 2% of benign vascular tumors and is frequently misdiagnosed because it mimics both benign and malignant vascular neoplasms (6). Most IPEH occur superficially, where high-frequency ultrasound is the reference modality for diagnosis and image-guided intervention (7). Due to its subtle clinical presentation and nonspecific radiological features, it is often misdiagnosed as malignant lesions such as angiosarcoma (3,5,8,9), making it crucial to carefully consider IPEH in both clinical and pathological diagnosis. Here, we report a case of Masson’s tumor occurring in the abdominal cavity which was initially suspected to be a neoplastic lesion, aiming to increase awareness and improve diagnostic accuracy for this rare condition. We present this article in accordance with the CARE reporting checklist (available at https://jgo.amegroups.com/article/view/10.21037/jgo-2025-635/rc).

Case presentation

A 52-year-old female patient presented with an incidental finding of a hypervascular mass in the left mid-to-lower abdomen during a routine abdominal computed tomography (CT) scan performed 2 weeks ago. The patient reported occasional dizziness and headaches over the past 5 years but had no history of abdominal bloating, fatigue, fever, weight loss, or other significant symptoms. Her weight had remained stable in recent months. Physical and laboratory examinations were unremarkable, and tumor markers were within normal limits.

Magnetic resonance imaging (MRI) showed a well-defined, round lesion in the left mid-to-lower abdomen, measuring approximately 40 mm × 32 mm × 34 mm. The lesion appeared as a low signal on T1-weighted imaging (T1WI) and a high signal on T2-weighted imaging (T2WI), with clear demarcation from surrounding tissues (Figure 1). High b-value diffusion-weighted imaging (DWI) demonstrated a slightly increased signal, corresponding to a mildly reduced apparent diffusion coefficient (ADC) (Figure 2). Post-contrast enhancement revealed a central nodular enhancement with a widening of the enhancement range during the venous and delayed phases (Figure 3). Based on these imaging findings, the lesion was considered possibly neoplastic due to its hypervascularity and deep intra-abdominal location; differential considerations included neuroendocrine tumor and gastrointestinal stromal tumor (GIST), although the progressive enhancement pattern did not strongly suggest malignancy. However, the centrifugal progressive enhancement pattern—characterized by central nodular enhancement in the arterial phase with gradual outward extension during the venous and delayed phases—was not suggestive of malignancy and is more compatible with the slow perfusion dynamics typical of benign vascular lesions. No alternative therapeutic strategies, including observation or image-guided biopsy, were pursued before surgery, as the lesion’s marked hypervascularity, deep intra-abdominal location, and overall imaging appearance raised sufficient concern for an underlying neoplastic process to justify direct surgical resection. The patient was therefore advised to proceed with operative exploration to obtain a definitive diagnosis.

Figure 1 Axial MRI section. An abnormal round lesion (arrows) is observed in the left mid-to-lower abdomen, with well-defined borders. The internal signal is homogeneous, appearing hypointense on T1WI (A) and hyperintense on T2WI (B). MRI, magnetic resonance imaging; T1WI, T1-weighted imaging; T2WI, T2-weighted imaging.

Figure 2 High b-value DWI (A) shows increased signal intensity (arrow), while ADC (B) demonstrates reduced signal intensity (arrow). ADC, apparent diffusion coefficient; DWI, diffusion-weighted imaging.

Figure 3 T1WI–derived mask. (A) Arterial phase imaging (B) shows marked enhancement of the lesion (arrow), suggesting a rich blood supply. Venous phase imaging (C) reveals a further expansion of the enhanced area compared to the arterial phase (arrow). Delayed phase imaging (D) demonstrates continued enhancement (arrow), presenting a “progressive filling” pattern. T1WI, T1-weighted imaging.

Following preoperative assessment, the patient underwent laparotomy under general anesthesia. The procedure included resection of the abdominal mass, partial resection of the small intestine, and placement of an abdominal drain. Postoperative pathology confirmed the diagnosis of IPEH (Masson’s tumor), with no abnormalities observed in the adjacent intestinal wall or mucosa (Figure 4). The patient had an uneventful postoperative recovery and was discharged on the fifth day following surgery. No complications were noted during the hospitalization. Six months after the surgery, the patient had no symptoms of recurrence. Follow-up abdominal ultrasound showed no abnormalities, and the patient was recovering well.

Figure 4 On hematoxylin and eosin (H&E) staining, focal areas within the lesion exhibit papillary structures lined by a single layer of flattened endothelial cells. Magnification: (A) original magnification, ×200; (B) original magnification, ×100.

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Discussion

In the literature, IPEH, also known as Masson’s tumor, accounts for 2–4% of reported cases of vascular tumors in the skin and soft tissues (3,5,9). It is more commonly observed in women. The exact etiology of Masson’s tumor remains unclear (10,11). Although approximately 70% of reported cases are considered idiopathic (12), it is generally thought to be a reactive endothelial proliferation following thrombosis, rather than a true neoplastic process: trauma leads to hematoma formation, which is accompanied by thrombosis, subsequent fibrosis of the thrombus, and the production of growth factors by circulating macrophages, thereby stimulating endothelial cell proliferation (10). Other potential triggering factors include hemangiomas, malformations, or pyogenic granulomas (11).

IPEH most commonly occurs in the skin, subcutaneous tissue, and mucosa, with frequent involvement of the hands, head and face, and oral cavity. However, it can also be found in the brain, spine, and deep soft tissues. The clinical presentation typically consists of a well-defined, non-pulsatile mass originating from the skin or subcutaneous tissue. The mass is firm, small in size, and does not adhere to or invade adjacent structures (10,12). Due to its nonspecific clinical and imaging features, IPEH is often misdiagnosed as angiosarcoma, hemangioma, or other vascular lesions, highlighting the importance of histopathological examination for definitive diagnosis (12-14).

IPEH can be classified into three types: (I) primary, occurring in normal blood vessels; (II) secondary, arising from pre-existing vascular lesions such as hemangiomas or arteriovenous malformations; and (III) ectopic, which is rare and usually develops at the site of an extravascular hematoma (15). In this case, the lesion was located in the left mid-to-lower abdomen, with no clear evidence of vascular malformation or other tumor background observed during surgery, suggesting it is more likely to be of an ectopic origin.

The clinical presentation of Masson’s tumor is often nonspecific and largely depends on the location and size of the lesion. Intra-abdominal lesions are usually discovered incidentally or may cause mild discomfort due to compression of adjacent organs. In this case, the patient reported no significant discomfort or obvious physical signs, suggesting the subtle nature of the lesion.

Radiologically, Masson’s tumor typically presents as a well-circumscribed, hypervascular solid mass with homogeneous internal density. Contrast-enhanced imaging often reveals intense enhancement during the arterial phase, followed by progressive or persistent enhancement in the venous and delayed phases. In this case, the MRI contrast-enhanced scan showed notable enhancement of the lesion during the arterial phase, with a further expansion of enhancement in the venous and delayed phases, exhibiting a progressive enhancement pattern. This dynamic enhancement feature is commonly indicative of a highly vascular lesion and should be differentiated from hemangiomas, metastases, and other vascular abnormalities.

When encountering a well-defined hypervascular mass with progressive enhancement and without washout or necrosis, benign vascular lesions such as IPEH should be considered to avoid misdiagnosis as malignancy. Neuroendocrine tumors and GISTs should also be included in the differential diagnosis of intra-abdominal hypervascular lesions, as these tumors can occasionally present with hemorrhagic complications. Contrast-enhanced CT in the arterial phase is crucial for detecting tumor-related bleeding. Although biopsy was not performed in the present case, in selected situations ultrasound- or CT-guided tissue sampling may assist in establishing a diagnosis and potentially avoid unnecessary surgery.

The enhancement characteristics of Masson’s tumor can be explained by the following mechanisms:

• Rich vascular structure: IPEH lesions are essentially endothelial cell proliferations within the vascular lumen. The lesion contains numerous capillary-like structures and varying degrees of thrombosis and organization, which explains the early enhancement seen in the arterial phase.
• Thrombus recanalization and slow perfusion: thrombotic tissue in IPEH may undergo partial recanalization and form new vascular pathways, leading to early enhancement of the vascular components in the arterial phase. Meanwhile, areas of fibrosis or organization exhibit delayed perfusion, resulting in delayed enhancement. This is similar to the “progressive filling” seen in benign vascular tumors.
• Normal permeability but prolonged blood pool: unlike malignant tumors, which show rapid “washout” of contrast agents, Masson’s tumor lacks abnormal leakage from newly formed capillaries. As a result, the contrast agent remains in the lesion for a longer period, leading to an expanded enhancement area in the venous and delayed phases, resulting in a “gradual filling” pattern.

This imaging feature suggests that while Masson’s tumor enhances significantly, it lacks the leakage and rapid clearance typical of neoplastic blood vessels, which helps differentiate it from high-grade malignant vascular tumors such as angiosarcomas. Angiosarcomas often show heterogeneous enhancement, rapid washout after early significant enhancement, accompanied by prominent necrosis, hemorrhagic foci, poorly defined borders, and invasion of surrounding tissues.

While this enhancement pattern may raise suspicion, it remains nonspecific and can closely mimic that of malignant vascular tumors. Consequently, preoperative imaging alone is rarely sufficient for a definitive diagnosis, which typically requires confirmation through postoperative histopathological evaluation.

Although this enhancement pattern may be suggestive, it lacks specificity. Neuroendocrine tumors and GISTs should also be considered in the differential diagnosis of intra-abdominal hypervascular lesions, as both neoplasms can occasionally present with acute or even severe hemorrhagic complications. Given the vascular nature of these tumors, contrast-enhanced CT with arterial-phase acquisition is regarded as the reference imaging modality for early detection of tumor bleeding. Recent reports have described cases of acute GIST hemorrhage demonstrated on CT, including the series by Picchi et al. (16).

As a result, preoperative imaging alone is often insufficient for definitive diagnosis, which usually relies on postoperative histopathological examination.

Histopathological examination is the gold standard for definitive diagnosis. At the histological level, IPEH can be distinguished from other conditions such as angiosarcoma based on its characteristic vascular location, papillary endothelial proliferation, organized thrombus formation, absence of tumor necrosis, cellular pleomorphism, and lack of mitotic activity (5,10,17).

IPEH is typically negative for GLUT1, while it is positive for WT1, CD31, CD34, α-smooth muscle actin (α-SMA), and factor VIII-related antigen (FVIII-RAg). CD105 is expressed only in true primary hemangiomas, making it a helpful marker for differentiating IPEH from other similar vascular lesions (17-19).

IPEH is a benign condition, and the gold standard treatment, as reported in the literature, is complete surgical resection. This approach can achieve full cure with a favorable prognosis, and generally, adjuvant radiotherapy or chemotherapy is not required (5,13,19). Studies indicate that patients who undergo complete surgical excision have good outcomes with minimal risk of recurrence. In this case, the patient recovered smoothly postoperatively, and no recurrence was observed during the 6-month follow-up, suggesting that early diagnosis and appropriate surgical intervention can lead to excellent results. However, there is still no consensus regarding the necessity of margin resection, and structured guidelines for postoperative follow-up are lacking (10). Recurrence is typically associated with incomplete excision (18). To date, there have been no reports of malignant transformation of IPEH (20).

This case is remarkable for several reasons. First, the abdominal cavity is an extremely rare location for Masson’s tumor, which typically occurs in the skin, subcutaneous tissue, head and neck, and limbs. Its occurrence in the abdominal cavity is exceptionally uncommon, making early identification challenging. Secondly, the patient’s imaging revealed significant enhancement during the arterial phase, with a hypervascular solid mass—features commonly seen in malignant vascular tumors, such as angiosarcomas or GISTs. As a result, the initial diagnosis leaned towards a tumor-like lesion. However, despite the imaging characteristics resembling those of malignant tumors, Masson’s tumor typically presents with well-defined borders and smooth margins, lacking the invasive growth patterns seen in malignancies. Moreover, it does not show the necrosis or hemorrhage commonly associated with malignant tumors. For these reasons, a definitive diagnosis could not be made based solely on imaging, and the final diagnosis was confirmed through postoperative histopathological examination. Histological analysis revealed papillary structures within the vascular lumen, along with positive immunohistochemical staining for CD31 and CD34, ultimately confirming Masson’s tumor. This underscores the diagnostic complexity of Masson’s tumor.

In addition, the patient’s postoperative recovery was noteworthy. As a benign lesion, Masson’s tumor has an extremely low recurrence rate after excision, contrasting sharply with the prognosis of malignant tumors. In this case, the patient experienced a rapid recovery and showed no signs of recurrence, further reinforcing the benign nature of Masson’s tumor and offering valuable clinical insights. Despite the rarity of abdominal Masson’s tumors, patients generally achieve excellent outcomes when the tumor is completely excised.

Conclusions

In conclusion, the uniqueness of this case lies in its rare abdominal location, the non-specific nature of its imaging findings, and the challenges involved in its diagnosis. It highlights the difficulties in diagnosing abdominal Masson’s tumor both radiologically and clinically, and provides an important strategy for differential diagnosis. When encountering a hypervascular mass with arterial phase enhancement, Masson’s tumor should be included in the differential diagnosis to ensure accurate identification and appropriate treatment, ultimately leading to favorable outcomes.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://jgo.amegroups.com/article/view/10.21037/jgo-2025-635/rc

Peer Review File: Available at https://jgo.amegroups.com/article/view/10.21037/jgo-2025-635/prf

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://jgo.amegroups.com/article/view/10.21037/jgo-2025-635/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Kuo T, Sayers CP, Rosai J. Masson's "vegetant intravascular hemangioendothelioma:" a lesion often mistaken for angiosarcoma: study of seventeen cases located in the skin and soft tissues. Cancer 1976;38:1227-36. [Crossref] [PubMed]
2. Lim R, Tay SC, Yam A. Intravascular papillary endothelial hyperplasia (Masson's tumour) of the finger presenting as a digital nerve schwannoma. J Hand Surg Eur Vol 2011;36:612-3. [Crossref] [PubMed]
3. Mitchell M, Riccio C, Mukit M, et al. Masson's Tumor of the Finger. Eplasty 2021;21:ic5. [PubMed]
4. Alsaif M, Alosaimi K, Alhassan T, et al. Intravascular papillary endothelial hyperplasia (Masson's tumor) of the finger: a case report and review of the literature. Case Reports Plast Surg Hand Surg 2025;12:2513066. [Crossref] [PubMed]
5. Mardani P, Askari A, Shahriarirad R, et al. Masson's Tumor of the Hand: An Uncommon Histopathological Entity. Case Rep Pathol 2020;2020:4348629. [Crossref] [PubMed]
6. Shamanna K, Krishnamurthy M, Deshpande GA. A Rare Case of Intravascular Papillary Endothelial Hyperplasia (Masson's Tumor) of Vocal Cord. Indian J Otolaryngol Head Neck Surg 2024;76:1317-20. [Crossref] [PubMed]
7. Corvino A, Catalano F, Cipolletta Campanile A, et al. Interventional Ultrasound in Dermatology: A Pictorial Overview Focusing on Cutaneous Melanoma Patients. J Ultrasound Med 2022;41:3137-44. [Crossref] [PubMed]
8. Patton A, Speeckaert A, Zeltman M, et al. A novel IRF2BP2::CDX2 Gene fusion in digital intravascular myoepithelioma of soft tissue: An enigma! Genes Chromosomes Cancer 2023;62:176-83. [Crossref] [PubMed]
9. Corni V, Lucchina S, Fusetti C. Is Masson's tumour only a slow-growing benign neoplasm? A case report. Hand Surg 2014;19:445-7. [Crossref] [PubMed]
10. Sung KY, Lee S, Jeong Y, et al. Intravascular papillary endothelial hyperplasia of the finger: a case of Masson's tumor. Case Reports Plast Surg Hand Surg 2021;8:23-6. [Crossref] [PubMed]
11. Patai BB, Peterfy N, Szakacs N, et al. Papillary Endothelial Hyperplasia (Masson Tumor) of the Hand. Surgical and Pathological Consideration from Seven Cases Using New Vascular Markers. Pathol Oncol Res 2020;26:2083-90. [Crossref] [PubMed]
12. Sasso SE, Naspolini AP, Milanez TB, et al. Masson's tumor (intravascular papillary endothelial hyperplasia). An Bras Dermatol 2019;94:620-1. [Crossref] [PubMed]
13. da Silva Leal M, Amado C, Paracana B, et al. Masson's Tumour: A Rare Cause of Cervical Mass. Eur J Case Rep Intern Med 2021;8:003078. [Crossref] [PubMed]
14. M Abdo E. Masson's Tumor as an Uncommon Cause of Neck Mass: A Case Presentation. Vasc Endovascular Surg 2024;58:405-9. [Crossref] [PubMed]
15. Soares AB, Altemani A, Furuse C, et al. Intravascular papillary endothelial hyperplasia: report of 2 cases and immunohistochemical study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:708-11. [Crossref] [PubMed]
16. Picchi SG, Lassandro G, Mazzotta G, et al. Urgent rare surgical complication assessment of intestinal gastrointestinal stromal tumors. J Endovasc Resusc Trauma Manag 2023;7:86-92.
17. Sartore L, Voltan A, Tomat V, et al. Masson's disease in hand surgery: a clinicopathologic study of four cases. J Hand Surg Eur Vol 2011;36:694-7. [Crossref] [PubMed]
18. Almarghoub MA, Shah Mardan QNM, Alotaibi AS, et al. Masson's tumor involving the hand: A case report. Int J Surg Case Rep 2020;70:223-6. [Crossref] [PubMed]
19. Chang K, Barlaben A, Farley S. Masson's tumor in the ulnar artery. J Vasc Surg 2012;56:223-5. [Crossref] [PubMed]
20. Voruz F, Arnoux G, Serex CA, et al. Intravascular papillary endothelial hyperplasia (Masson's tumor) of maxillary sinus. Braz J Otorhinolaryngol 2022;88:141-5. [Crossref] [PubMed]