Laparoscopic splenectomy for sclerosing angiomatoid nodular transformation of the spleen.

Sclerosing angiomatoid nodular transformation (SANT) is a rare, benign, proliferative vascular lesion that arises from the splenic red pulp. Most patients with SANT have no clinical symptoms and are discovered incidentally on imaging. There are no definitive radiological signs and a distinction from other splenic diseases, and malignant processes remain difficult. Confirmation of the diagnosis of SANT requires a histological and immunohistochemical evaluation of the resected spleen. Here, we report an unusual case of SANT of the spleen successfully treated with an elective laparoscopic splenectomy (LS). LS is a safe and effective method for diagnosis of SANT.

INTRODUCTION

Sclerosing angiomatoid nodular transformation (SANT) is an extremely rare benign tumour of the spleen that was recognised as a distinct pathological entity in 2004.[1] SANT is a vascular neoplasm that differs from angiomas by the heterogeneity of its vascular components. However, pre-operative radiological diagnosis is troublesome as key imaging features are lacking. Recently, laparoscopic splenectomy (LS) has become the standard technique for the surgical management of haematological splenic diseases and tumours. We present a case diagnosed as SANT of the spleen after LS.

CASE REPORT

A 46-year-old woman was admitted to our hospital with abdominal discomfort and mild anaemia (haemoglobin 11.3 g/dl). Physical examination and biochemical parameters were unremarkable. Ultrasonography (US) demonstrated a hypoechoic splenic mass of large diameter, 60 mm, without any defined additional feature. For this reason, the patient underwent an abdominal magnetic resonance imaging (MRI) which confirmed a solid formation of approximately 56 mm × 46 mm in the axial plane, in the middle third of the spleen parenchyma. The mass appeared with polylobulated nodules, overflowing onto the front edge of the spleen, without invading of the neighbouring structures. The lesion showed a widespread and progressive centripetal filling following the administration of intravenous contrast, except for the central portion, due to the fibrous tissue [Figure 1].

Figure 1

Magnetic resonance T1-weighted images following the administration of intravenous contrast agent. (a) Arterial phase shows enhancement of the periphery of the lesion. (b) Venous phase shows centripetal filling. (c) Post-contrast 10-min delayed confirms a progressive centripetal filling, with a central hypointense focus. (d) Magnetic resonance T2-weighted shows the lesion to be mildly hypointense, with a central hyperintense focus

The radiologic images were discussed in our sarcoma multidisciplinary team meeting. Although no clear suspicion of a malignancy process emerged, the atypical radiological findings suggested LS. The procedure was performed in the right lateral decubitus position. The pneumoperitoneum was established with the open technique, and three trocars were inserted along the left subcostal margin. The splenic flexure of the colon was detached and the stomach mobilised after the division of the short gastric vessels. The splenic hilum was isolated and divided using an endovascular stapler. The spleen was placed in a plastic bag and extracted through a small left hypochondrial incision.

The spleen measured 115 mm × 73 mm × 50 mm and weighed 225 g. Macroscopically, it presented multiple subcapsular solid nodules, non-encapsulated, with polycyclic margins and a trabecular meshwork aspect. On histopathology, the spleen was composed of multiple, variably sized, circumscribed and confluent angiomatoid nodules immersed on a fibrosclerotic stroma. The morphological and immunophenotypic appearance was diagnostic for SANT [Figure 2].

Figure 2

Sclerosing angiomatoid nodular transformation of the spleen, histopathological findings. (a) Nodules are composed of slit-like, round-shaped vascular spaces lined by plumps endothelial cells (H and E, ×2). (b) Sinusoidal-Like vascular spaces show strong immune reactivity for CD8 (Immunoperoxidase, ×10)

The patient had a regular post-surgical period and was discharged 5 days after surgery without complications.

DISCUSSION

SANT is a rare, benign vascular lesion first described in 2004 by Martel et al.[1] As SANT is a vascular lesion comprised an over-proliferation of blood vessels, its differential diagnosis includes benign lesions such as hamartomas, haemangiomas, haemangioendotheliomas, littoral cell angiomas, inflammatory myofibroblastic lesions and malignant lesions. Histopathologically, SANT is composed of angiomatoid nodules separated by central stellate fibrous stroma and fibrous septa. Patients are often asymptomatic and present an incidental splenic mass on radiology.

The conventional US is not characteristic, showing a hypoechoic lesion with no specific signals during the colour-Doppler examination. Contrast-enhanced US can provide more morphological information than conventional US.[2] Contrast-enhanced computed tomography or MRI, generally reveals a centrally hypovascular lesion with peripheral enhancement progressively extending towards the centre of the lesion through septae on delayed imaging, with a so-called 'spoke-wheel’ appearance.[3] Although it may be possible to differentiate benign and malignant splenic lesions with a combination of clinical history and radiological imaging, there are no defined imaging patterns of SANT. For this reason, it is mandatory to have a pathological confirmation for diagnosis of SANT.

Splenectomy has become the choice procedure for haematologic disorders and splenic tumours and is considered diagnostic in the presence of a spleen lesion suspected for malignancy. Compared with open splenectomy, LS limits wound incision, reduces post-operative pain and complications and provides a better quality of life. The existing literature revealed that few cases of SANT were treated with LS.[456] In one case, a laparoscopic partial splenectomy was performed.[7] The key features characteristic of SANT reported in the case reports has been compared [Table 1]. Early peripheral arterial enhancement with subsequent centripetal filling was noted in almost all cases following the administration of intravenous contrast agent.[456] This is concordant with the gross pathologic appearance of a central fibrous stroma and peripheral nodules of angiomatoid tissue. T2-weighted MRI typically shows peripheral hypointensity with a central hypointense focus. However, the presence of a characteristic hypointense central scar on T2-weighted MR, is not observed in all patients with SANT,[5] probably due to extensive haemangiomatous lesions in addition to the angiomatoid nodules, as in our case. No recurrence was observed during follow-up. At this level of evidence, it seems prudent to proceed with LS in all patients with splenic masses, even asymptomatic, presenting with inconclusive radiological features, as herein we reported.

Table 1

Clinical and radiological features of four cases of sclerosing angiomatoid nodular transformation of the spleen treated by laparoscopic splenectomy

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Nil.

Conflicts of interest

There are no conflicts of interest.