Table 1. The summary of findings of the selected studies.

USG: ultrasonography, MRI: magnetic resonance imaging, CT: computed tomography, MRV: magnetic resonance venography, PET: positron emission tomography, IJV: internal jugular vein, LCH: lobular capillary hemangioma, EJV: external jugular vein, SVC: superior vena cava, CTA: computed tomography angiography, DUS: Doppler ultrasound, ILCH: intravascular lobular capillary hemangioma

Author	Year	Location	Age	Gender	Diagnostic modality	Clinical findings	Intervention	Prognosis
Ulbright and Cruz [12]	1980	United States	12	Male	Physical examination	A 1.5-cm nontender, firm, and mobile nodule was palpated in the subcutaneous tissues of the right side of the neck. Histologically, the lesion displayed an intravascular projection on the vein wall's luminal side, comprising capillary proliferation with pronounced endothelial cells and myxoid stromal regions. Elastic fiber disruption was evident at its attachment. Electron microscopy emphasized capillary and stromal components.	Surgical excision	No recurrence was observed in the one-year follow-up.
Truong and Font [13]	1985	United States	44 and 68	Male	Biopsy	The features were mostly similar in both cases. Well-circumscribed, ovoid masses were easily removable from surrounding soft tissues and composed of discrete or confluent lobules of capillaries surrounded by fibromyxomatous stroma. Capillaries with variable sizes and round, oval, or angular lumina, mild nuclear hyperchromatism but no pleomorphism in the endothelial cell lining, and scattered mitotic figures were observed in endothelial cells. Poorly cellular intervening stroma with myxomatous matrix, collagen, reticulin fibers, and scattered lymphocytes; prominent vascular channels within the stroma, resembling small arteries or dilated venules. Absence of endothelial-lined papillary fronds, thrombi, surface ulcération, and granulation tissue. Non-invasion of the vein wall by the angiomatous proliferation.	Surgical excision	Case 1: The patient was reported to be in good health, without evidence of recurrence, seven years and eleven months after surgery. Case 2: The patient was alive and well, without evidence of recurrence, four years and seven months after surgical excision.
Pesce et al. [8]	1996	England	20	Male	Excisional biopsy	A cribriform, textured mass measuring 0.8x0.4 cm. Cellular stroma with plump fibroblasts and sparse lymphocytes. Slit-like luminal spaces were observed in some areas with thin endothelial lining. Mass adhered to the intima in some areas and was disrupted by capillary proliferation in the media in other areas. Parallel sections showed fibrous stroma with haphazardly arranged small vessels and a bland endothelial lining. Instances of capillaries abutting perineurial spaces were observed.	N/A	N/A
Margo [14]	1994	United States	27	Male	Biopsy	A muscular artery with a well-developed internal elastic membrane. Approximately one-third of the internal elastic membrane was replaced with fibrous connective tissue and disorganized smooth muscle cell proliferation. The lumen of the artery was filled with a polypoid mass of richly vascular tissue attached to the vessel wall. Plump and spindle-shaped endothelial cells with inconspicuous vascular lumina and sparse extracellular stroma. Presence of fibrin thrombi and chronic inflammatory cells, including eosinophils.	Surgical excision	N/A
Panchagnula and Kini [15]	2001	India	12	Female	Excisional biopsy	Interwoven thick and thin-walled blood vessels extend into the surrounding tissue. Intraluminal lobular masses, resembling "glomerulations," contained proliferating capillaries lined by prominent endothelial cells. FVIII antigen positivity.	Surgical excision	No recurrence was observed in the 1- to 1.5-year follow-up.
Hung et al. [4]	2004	Taiwan	44	Female	Excisional biopsy	A tender, dark-red to purplish eroded nodule was observed on the patient's right palm, featuring a hyperkeratotic collar and measuring 6x6 mm. Histological analysis revealed an elevated epidermal area containing multiple lobules of dilated and congested capillaries within vascular spaces in the papillary dermis. The epidermis displayed hyperkeratosis and papillomatosis. The deep dermis contained a collection of thick-walled vessels of varying caliber, largely lacking muscular elements. The Verhoeff-van Geison stain showed some areas of positive staining, suggesting an arteriole-like structure with elastic fibers.	Surgical excision	No recurrence was observed in the six-month follow-up.
Jung et al. [16]	2008	Korea	51	Male	USG, incisional biopsy	Clinical assessment revealed an oval subcutaneous mass measuring around 2×1 cm. Ultrasonography revealed a longitudinally elongated hypoechoic mass with limited inner vascularity within the cephalic vein. The tumor consisted of capillary lobules set in an oedematous fibromyxoid stroma, aligning with pyogenic granuloma.	Surgical excision	N/A
Pradhan et al. [6]	2008	United States	75	Female	CT scan, MRV, arteriography	CT scan showed an intraluminal tumor in the right internal iliac vein. MRV revealed an incompletely obstructing 2.4x1.8 cm mass in the right internal iliac vein, extending to the distal inferior vena cava. The arteriogram showed neovascularization of an intravenous mass. Intraoperative ultrasound showed the presence of a mass within the internal iliac vein extending into the inferior vena cava.	Surgical excision	No recurrence was observed in the two-month follow-up.
Barr and Vincek et al. [17]	2010	United States	45	Male	Physical examination, biopsy	Round, soft, moveable, deep dermal mass (1 cm in diameter) on the forehead. Histology showed a multilobulated tumor of capillaries separated by fibrous septae set in an edematous fibromyxoid stroma located in the deep subcutis, close to the frontalis muscle. CD31 staining performed to outline vessel distribution demonstrated the intravascular location of the lesion.	Surgical excision	N/A
Gamerio et al. [18]	2016	United States	54	Male	Incisional biopsy	Histology showed the proliferation of multiple well-circumscribed lobules (round-shaped or elongated) composed of packed capillary vessels lined by bland endothelial cells. A prominent population of pericytes surrounded the vessels.	Surgical excision	The lesion completely regressed within two weeks, and a disfiguring scar resulted from the regression.
Dermawan et al. [19]	2020	United States	13 to 85	Male(n=18) Female(n=22)	Biopsy	In ILCH cases, a distinct nodular or lobular growth pattern was evident, characterized by densely packed capillaries with central ectatic vessels. About half of the cases exhibited a clear peripheral vascular wall. Even in cases lacking visible peripheral walls, the well-defined growth pattern persisted. Multinodular growth was observed in some instances. Vascular spaces were lined by unremarkable endothelial cells, with hobnail features seen in 28% of cases. Approximately 25% displayed heightened mitotic activity (>5 mitotic figures/10 high-power fields), and mild cellular atypia was evident in 11% of cases. A significant inflammatory component was absent in the majority (75%) of cases. The presence of a pericyte layer encircling vessels was consistently highlighted by SMA staining. Notably, all cases exhibited diffusely positive WT1 staining in endothelial cells.	Surgical excision	The median follow-up period was 40 months (range: 7 to 153 months). Out of 21 cases, none of them recurred following surgical resection.
Balya et al. [20]	2021	France	35	Female	DUS, CTA, MRI, PET	DUS showed collateral vein dilatation. CTA revealed an intraluminal heterogeneous mass within the SVC, extending from the left brachiocephalic venous trunk to the distal third of the SVC. Thoracic MRI confirmed the intraluminal location of the SVC tumor, measuring 80x33 mm with a cystic component. Heterogeneous T1- and T2-weighted signals were evident. PET showed moderate fluorodeoxyglucose enhancement. Pathological examination demonstrated a tumor measuring 55x34x25 mm occupying the SVC lumen. Microscopic analysis unveiled a vascular lesion with lobular architecture, comprising capillaries lined by unstratified endothelium and fibro-oedematous stroma. Immunohistochemical analysis yielded positive vascular markers (CD31 and ERG) and a low Ki67 proliferation index.	Surgical excision	No recurrence was observed in the seven-month follow-up.
Ikeda et al. [21]	2021	Japan	72	Female	USG, CT, MRI	The left cephalic vein appeared enlarged. Ultrasound examination revealed a space-occupying lesion within the left subclavian vein, with no Doppler signal detected. The diameters of the left internal jugular vein were 6.0 mm (in a straight position) and 12.0 mm (during neck anteflexion), whereas the right internal jugular vein diameters were 3.0 mm (in a straight position) and 2.0 mm (during neck anteflexion). A potential venous thrombosis in the left subclavian vein was suspected, leading to the initiation of oral anticoagulant treatment. Following two weeks of treatment, ultrasonography indicated no change in the mass. The mass was surgically excised, and histopathological examination showed intravenous capillary haemangioma	Surgical resection	The sensation of pressure in the patient's left neck disappeared after the operation. The patient did not experience neck discomfort while cooking after discharge.
Jing et al. [2]	2021	China	38	Male	USG, biopsy	Ultrasound showed a well-defined nodular intraluminal mass within the basilic vein, measuring approximately 8x2x6 mm. A mainly hypoechoic and heterogeneous structure was observed, containing distinct anechoic tunnel-like structures. Abundant blood flow signals were evident on color Doppler flow imaging, supplied by surrounding tissue vessels. A pulsed Doppler examination recorded typical arterial signals within the lesion. A macroscopic examination revealed a well-defined polypoid mass connected to the venous wall. Microscopic analysis unveiled flattened endothelial cells lining capillaries in a lobular arrangement, separated by a fibrous mucinous stroma. Immunocytochemical staining confirmed vascularity with positive CD34 and ERG staining.	Surgical excision	No recurrence was observed in the three-month follow-up.
Kaiser et al. [22]	2021	Switzerland	26	Female	Excisional biopsy	Histopathological findings were typical of ILCH.	Surgical excision	No recurrence was observed in the three-month follow-up.
Tucciarone et al. [23]	2021	Spain	69	Female	CT scan, echography biopsy	Presence of a movable and non-pulsating mass along the EJV. An echography scan identified a 15x8 mm intraluminal lesion within the EJV. Doppler scanning revealed inherent arterial and venous blood flow. CT scan verified a non-occlusive intraluminal neoformation within the EJV. Subsequent histopathological examination definitively confirmed the presence of intravenous lobular capillary hemangioma.	Surgical excision	No recurrence was observed in the two-year follow-up.
Fakoory et al. [1]	2022	West Indies	47	Male	Biopsy, vascular USG	2x6 mm of soft, painless swelling along the trajectory of the temporal artery was identified. Vascular ultrasound identified thrombosis in the right temporal artery. Macroscopic analysis revealed multiple pieces of tan-gray tissue. Microscopic evaluation revealed a nodular vascular lesion characterized by small capillaries arranged in lobules. Immunohistochemistry demonstrated robust cytoplasmic positivity for CD31, CD34, and factor VIII.	Surgical excision	N/A
Zhou et al. [24]	2016	China	26	Female	USG, biopsy	A painless oval mass measuring 2x2 cm on the wrist's ulnar side. Ultrasound revealed an irregular low-echo area. Microscopic examination showed hypertrophic capillaries in clusters with clear borders and fibrous tissue in between, resembling LCH but without ulceration or inflammation. CD34, SMA, and FVIII positivity were observed.	Surgical excision	No recurrence was observed in the three-month follow-up.
Yang et al. [25]	2021	China	44	Male	Color Doppler USG, MRI, CT, biopsy	Doppler ultrasound revealed an abnormal echo within the left IJV, displaying hypoechoic patterns, irregular shape, and clear boundaries. Color Doppler showed a filling defect and microvascular imaging detected star-like flow signals. Contrast-enhanced USG demonstrated uneven enhancement during arterial and venous phases. CT and MRI confirmed an isodense pedunculated nodule in the IJV, ruling out thrombosis and suggesting endoluminal neoplasia. Immunohistochemical staining results showed CD34, CD31, ERG, VIM, and KI67 positivity with SMA negativity.	Surgical excision	No recurrence was observed in the three-month follow-up.