Case report and magnetic resonance images of sclerosing angiomatoid nodular transformation (SANT) of the spleen

Abstract

A 40-year-old woman presented with a 2 year history of intermittent left upper quadrant pain. The clinical examination and blood tests were normal, but the pain persisted. An ultrasound scan of the abdomen revealed a hypoechoic mass in the spleen which was further investigated by computed tomography and magnetic resonance imaging (MRI). The differential diagnosis included solitary lymphoma, splenic haematoma, sarcoma, solitary metastasis or partially thrombosed splenic artery aneurysm. The patient underwent elective splenectomy and histology showed the appearance of a rare tumour. We present MRI images of this very rare splenic tumour.

Background

The majority of non-lymphoid primary tumours of the spleen are vascular in nature. Wide ranging histological features of these vascular lesions render classification very difficult. A group of lesions with characteristic morphological features, distinctive immunophenotypic profile and benign clinical course have been designated as sclerosing angiomatoid nodular transformation (SANT). These are very rarely reported and are only diagnosed following excision and histology. We hope our report, which presents rare magnetic resonance images, will help in the preoperative diagnosis of these malignancies.

Case presentation

A 40-year-old woman presented with persistent intermittent left upper quadrant pain. At the time of her review in the clinic she did not have any symptoms other than intermittent left upper quadrant pain. The physical examination was normal.

Investigations

Blood tests including full blood count, urea and electrolytes, liver function tests, carcinoembryonic antigen, Ca125 and Ca 19–9 were within normal limits. She had two gastroscopies which were normal. Ultrasound revealed a 5.2×5.1×4 cm, well defined, hypoechoic mass within the splenic hilum. Computed tomography (CT) scan of the chest, abdomen and pelvis, and subsequent magnetic resonance imaging (MRI) scans were requested and reviewed in a multidisciplinary meeting (figs 1–5).

Figure 1.

The vibe sequence. This is a T1 weighted sequence and the lesion is smooth in contour, measuring 4×4.6 cm; it is exophytic and arises from the region of the splenic hilum. The lesion is of similar T1 signal to the adjacent liver (parenchyma).

Figure 5.

Delayed phase following gadolinium (T2). There is evidence of some slightly irregular central washout.

Figure 2.

The short field echo T2 weighted image. The T2 signal is low compared to adjacent splenic parenchyma, indicating lack of water/oedema. This appearance is seen in tumours of increased cellularity or fibrosis.

Figure 3.

Outer phase T1. Gradient echo sequence with a stencil artefact due to chemical shift showing no appreciable loss of T1 signal in outer phase imaging, indicating absence of intralesional fat. The lesion itself was heterogeneous in intensity, suggestive of a haemorrhagic component.

Figure 4.

Portal Venus phase image (T2). In the portal Venus phase the lesion is relatively avidly enhancing and is certainly of increased enhancement compared with adjacent splenic parenchyma.

Differential diagnosis

At this point the differential diagnoses were solitary lymphoma, splenic haematoma, sarcoma, solitary metastasis or partially thrombosed splenic artery aneurysm. Given its vascular nature, a biopsy was not performed and it was decided that splenectomy was appropriate.

Treatment

A standard open splenectomy was carried out and the complete specimen was sent for histopathology. The patient had an uncomplicated postoperative recovery and was discharged home.

Outcome and follow-up

On examination the spleen weighed 168 g and the cut surface showed a peripheral circumscribed nodule measuring 4.7×4.0×6.5 cm which was partly fibrous and partly nodular haemorrhagic in appearance. Microscopic findings were consistent with sclerosing angiomatoid nodular transformation (SANT), and showed a spleen containing a well circumscribed lesion with multinodular architecture which appeared granulomatous on low power. Nodules were highly vascular with hyaline collagenous outlines and are composed of masses of small slit-like vessels with extravasation of fibrin and red cells (figs 6 and 7). Immunohistochemical studies revealed RUI: CD3+T cells =38.6%, of which 43% are CD4+ helper cells and 51% are CD8+ cytotoxic cells; CD16+NK cells =8.5% of leucocytes; CD19+B cells = 41.2% of leucocytes, kappa: lambda ratio = 1.6:1 (normal) (fig 8). These are consistent with SANT of benign splenic lesion.^1,2

Figure 6.

Slide showing loss of loss of normal splenic architecture, with fibrosis surrounding the areas of angiomatoid change. Haematoxylin and eosin ×4.

Figure 7.

Higher magnification of slide showing loss of loss of normal splenic architecture, with fibrosis surrounding the areas of angiomatoid change. Haematoxylin and eosin ×10.

Figure 8.

Immunohistochemical studies. CD 34×10.

Discussion

Our report provides MRI images (figs 1–5) of a rare tumour, which is a useful addition to the characterisation and diagnosis of SANT of the spleen. This has been reported rarely in the literature.^1,2 We feel MRI may have a useful role in the diagnosis of this rare tumour of the spleen which, if made, can be managed conservatively.

Comparison of these MRI images with previously published images³ showed similar appearances in both cases, as described. In both cases T1 images were suggestive of a haemorrhagic component which was a contraindication for biopsy preoperatively. T2 images were similar in both cases, as described. Central fibrosis was also present in both the cases. The only difference was that there was no spoke wheel pattern in our images as described previously. There were no other radiological abnormalities in either case.

Learning points

• MRI images of a very rare tumour, sclerosing angiomatoid nodular transformation (SANT) of the spleen, are presented.