Sclerosing angiomatoid nodular transformation of spleen: a rare case report

Summary

Sclerosing angiomatoid nodular transformation (SANT) of the spleen is a relatively rare non-neoplastic proliferative mass of vascular origin arising from the red pulp of the spleen accounting for less than 1% of all splenic tumors. Accurate preoperative diagnosis is difficult due to the rarity of the pathology and lack of specific clinical and radiologic features, and final diagnosis of SANT is based on histopathologic and immunohistochemical studies. A 34-year-old male patient who presented with an incidentally found tumor of the spleen discovered on a routine CT examination. The patient underwent classic splenectomy. Pathological examination with immunohistochemical staining confirmed SANT of the spleen. SANT should be included in the differential diagnosis of focal pathology of the spleen due to the rarity of this disease and should be treated by further open or laparoscopic splenectomy with pathologic examination including mandatory immunohistochemical staining.

Keywords:

splenectomy – Spleen – case report – sclerosing angiomatoid nodular transformation

Introduction

Sclerosing angiomatoid nodular transformation (SANT) of the spleen is a relatively rare benign proliferative mass of vascular origin arising from the red pulp of the spleen ­[1–4]. SANT is defined as a non-neoplastic condition and is exclu­sively localized in the spleen [4]. According to Loizides et al. (2024), SANT accounts for less than 1% of all splenic tumors [5].

Accurate preoperative diagnosis is difficult due to the rarity of the pathology and lack of specific clinical and radiologic features, and final diagnosis of SANT is based on histopathologic and immunohistochemical studies [2,5,6]. We present our own clinical observation with a brief review of the literature on the diagnosis and surgical treatment of this pathology, taking into account the rarity of SANT. The case report narrated with Surgical Case Report (SCARE) 2023 guideline [7].

Case report

A 34-year-old male patient, otherwise healthy, presented with an incidental mass of the spleen discovered on a routine computed tomography (CT) examination. Physical examination and laboratory findings were unremarkable. Abdominal CT revealed a non-enlarged spleen with a well-defined, enhancing mass measuring 88 × 71 mm (Fig. 1).

The patient underwent classic splenectomy (CS) during which a firm spherical mass measuring approximately 8 × 7 cm in diameter was discovered in the upper pole of the spleen, with intact capsule (Fig. 2A). The surgery lasted 60 min, and the estimated intraoperative blood loss was around 80 mL. The postoperative course was uneventful, and the patient was discharged on the 7^th day postoperatively.

Macroscopic examination of the resected spleen revealed a well-circumscribed solitary lesion contained a central white stellate structure (Fig. 2B). Thus, SANT was suspected macroscopically.

Pathological examination confirmed SANT of the spleen, capillary type, with positive staining for CD8, CD31, and CD34, as well as SMA and CD68 (Fig. 3A, B). The patient remains disease-free during a 6-month follow-up period, with no recurrence and abnormalities in hematological examinations.

Discussion

This pathology was first described by Krishnan in 1993 as “cord capillary hemangioma” and the term SANT was introduced by Martel et al. (2004) based on 25 cases with typical morphological features of vascular lesions of the spleen [1]. Based on a systematic review published by Aziret et al. [2], 230 cases of SANT have been described in the literature until April 2020. According to López Rojo et al. (2025), despite the rarity of SANT, there has been a recent increase in the number of cases of this pathology published in the literature [8].

The etiopathogenesis of SANT has not yet been established [1,2,8]. However, a possible association of this pathology with Epstein-Barr virus infection and immunoglobulin G4 (IgG4)-associated fibrotic inflammatory diseases has been hypothesized in the literature [5,9,10]. This pathology is slightly more common in women (52.1%) between 30 and 60 years of age, with a mean age of 42–46 years [2,3]. At the same time, according to Kim et al. (2025), 10 cases of SANT in pediatric patients (age < 18 years) have been published in the English-language literature [11]. Half of patients with SANT are asymptomatic and these masses are discovered incidentally during evaluation for other conditions [2,3,5,6,8,10,12]. The clinical presentation of SANT is non-specific and includes upper abdominal pain or discomfort [4,6,11], bloating, distention, left upper quadrant or epigastric pain, fever or night sweats, weight loss, and dyspepsia [2,3,13].

Medical history analysis revealed the presence of comorbidities (including malignancies) affecting multiple organs and systems, including the gastrointestinal tract, hematopoietic system, biliary tract, and adrenal glands [3,5,7,13]. Splenomegaly was found in some cases (8.2%) by clinical examination and imaging [2,4]. In very rare cases, thrombocytopenia was observed during laboratory testing [2,3]. Differential diagnosis should include hemangioma, hamartoma, lymphoma, angiosarcoma, inflammatory pseudotumor, and malignant neoplasm metastasis [2,3,5,7,11].

Transabdominal ultrasonography usually reveals a solid hypogenic mass [2,8]. It has been observed that SANT is predominantly a solitary mass in most cases [4,6,11,14] and multiple masses in only 10% of cases [2,3]. On native CT, 65% of SANTs were visualized as a homogeneous, hypodense mass with distinct smooth or lobulated contours [5–8,11,14], and in 15.6% of cases, calcinates were identified in the mass [3,6,14]. After contrast introduction in 59.4% of cases radiologists found typical pattern of enhancement in the form of radial, star-shaped configuration, “spoke wheel” [3,6,14] or “cart wheel” [7].

Magnetic resonance imaging (MRI) visualized low signal scars on T2-weighted images (T2WI) in 100% of cases, with all of these scars showing enhancement [5,14], and signals indicative of hemosiderin in 70.8% of cases. After contrast administration, a “spoke wheel” pattern of enhancement was seen in 65% of cases, while nodular enhancement was seen in 35% of cases [7,14]. In addition, branches of the splenic artery crossing the mass were noted in 40% of cases [3]. In 18F-fluoro-2-deoxyglucose (18-FDG) positron emission tomography (PET) scan, a standardized uptake value (SUV: from 3.3 to 7.2) was observed in the region of spleen tumor and the absence of this phenomenon in the unaltered parenchyma of the organ [5,8,14].

Despite the use of modern imaging techniques (CT with contrast, MRI), the accurate diagnosis of SANT is difficult because radiological signs are similar to malignant tumors (metastases) [3,5,7]. According to imaging methods, the correct preoperative diagnosis is established in 26.9–30% of SANT cases [2,3].

In general, splenectomy (SE) is considered a first-line option in the management of SANT [2,3,11] and is also considered diagnostic for residual suspected metastatic lesions [5,7]. According to a systematic literature review, open SE was performed in 72.1% of SANT cases, laparoscopic SE 15.2% and laparoscopic partial SE 6.5% [2]. The performance of SE through laparotomy access in most cases was justified by preoperative diagnostic data indicating a high probability of malignant growth (metastases) or extensive abdominal surgery in the patient’s history [4,8]. With the widespread introduction of minimally invasive surgery, there has been a progressive increase in the use of laparoscopic techniques for SE [2,3,10,11,13].

On macroscopic section, SANT is a well circumscribed dense mass without a capsule, grayish red or whitish brown in color with a large central stellate scar [2–4,6,14]. The size of SANT ranged from 2.0 to 17 cm and the average weight was 260 g (68 to 2,720) [2–4,14]. Microscopic examination of SANT is characterized by multiple confluent angiomatous nodules surrounded by variable concentric fibrosclerotic stroma and well demarcated from the splenic parenchyma [11]. Angiomatous nodules contain blood vessels of various diameters with extravasation of erythrocytes. Abundant collagen fibers are visualized along the periphery of the nodules [2–4,8]. The absence of atypia, mitotic activity and necrosis has been noted [7].

Immunohistochemistry shows positive expression to CD8, CD31, and CD34 [5–8,14]. Three different vascular variants in the angiomatous nodule are described: 1. capillary type (CD34⁺/CD8^–/CD31⁺); 2. sinusoidal type (CD34^–/CD8⁺/CD31⁺) and 3. small venous type (CD34^–/CD8^–/CD31⁺), reproducing the components of splenic red pulp in normal spleen [1,8,15]. In the SANT series (N = 40) published by Xiang et al. (2025), a predominant capillary type was observed in 92.5% of cases, a sinusoidal type in 5% and a small venous type in 2.5% [3]. Positive expression of α-smooth muscle actin and factor VIII was also noted [13]. According to most authors, SANT after SE has a favorable prognosis and absence of recurrence in the distant postoperative period [2,4,6,7,13]. Moreover, according to López Rojo et al. (2025), due to the benign nature of SANT, no specific subsequent surveillance is required [7].

Conclusion

Sclerosing angiomatoid nodular transformation (SANT) is a rare benign pathology of the spleen and should be included in the differential diagnosis of focal pathology of this parenchymal organ. Open or laparoscopic splenectomy should be considered both as a therapeutic and diagnostic procedure. Immunohistochemistry (CD8, CD31 and CD34) is mandatory to establish the final diagnosis.

Conflict of interests

The authors declare that they have no conflict of interest related to the creation of this article, and that this article has not been published in any other journal with access to congress abstracts.