Sclerosing angiomatoid nodular transformation of the spleen: unusual case presentation in an intravenous drug user

Background

Sclerosing angiomatoid nodular transformation (SANT) is a rare, recently recognised and defined in 2004,1 non-neoplastic benign vascular lesion of the spleen with unknown aetiology.2 3

Most patients are asymptomatic with majority of these lesions found incidentally on imaging,2 4 although as many as 16% complain of abdominal pain which is reported as being the most predominant symptom if present.2 While these tumours show characteristic radiological findings reflecting the underlying pathology, the differential diagnosis from other splenic tumours or malignant lesions is quite challenging and a confirmed diagnosis of SANT requires histopathology analysis.4

Our aim is to bring further attention to this rare condition.

Case presentation

A 42-year-old man with a history of the bicuspid aortic valve with aortic regurgitation and dilated root of the aorta (EF >55% and an aortic root of 4.8 cm), active smoker, intravenous drug user and previously hepatitis C antibody positive/antigen negative in 2013, taking methadone 40 mL one time a day and ramipril 1.25 mg one time a day, was admitted to University Hospital’s emergency department with symptoms of generalised weakness and a feeling of being unwell for a week with several episodes of vomiting and headaches.

At the time of presentation, his temperature was 37.1°C, heart rate 71 bpm, respiratory rate 20 breaths per minute, SpO₂ 99% and blood pressure was 101/60 mm Hg. Initial laboratory investigations included erythrocyte sedimentation rate (ESR) 16 mm/hr, alanine aminotransferase (ALT) 978 IU/L, alkaline phosphatase (ALP) 295 IU/L, total bilirubin 93 umol/L and was diagnosed with hepatitis C genotype 1A infection in the context of recent intravenous drug use.

Investigations

During his admission, he underwent an ultrasound of the abdomen (figure 1) showing a large periportal lymph node, measuring up to 1.4 cm in short axis, possibly secondary to the hepatitis and splenomegaly (16.71 cm) with a suspected 7–8 cm hypoechoic mass in the lower pole concerning for lymphoma. On the basis of these results, a CT thorax, abdomen and pelvis (TAP) was advised for further evaluation.

CT TAP was performed with findings corresponding to the abnormality demonstrated on ultrasound: splenomegaly measuring 18.3 cm in interpolar length and a poorly defined slightly hypo-attenuating and relatively heterogeneous mass in the inferior pole of the spleen measuring approximately 7.2×7×8.5 cm (figure 2). This was reported to be suspicious for malignancy, most likely lymphoma, and a biopsy was recommended to confirm this hypothesis. Of note, the CT also demonstrated a simple cyst in segment IV of the liver, multiple mildly prominent upper abdominal nodes which did not reach the size criteria for enlargement and were deemed of uncertain clinical significance along with multiple indeterminate pulmonary nodules bilaterally that were advised to be followed on subsequent CT examinations.

An MRI of the upper abdomen was performed. This was reported and compared with previous imaging. The MRI demonstrated and reconfirmed the presence of an 8 cm in diameter splenic mass with moderate enhancement, suspicious for malignancy (figure 3).

The patient was reviewed by haematology and a bone marrow biopsy was performed. The aspirate showed no evidence of lymphoma. An ultrasound guided biopsy of his spleen was arranged showing features suggesting a vascular proliferation either neoplastic or reactive. Although there was no overt evidence of lymphoma or high-grade sarcoma, the features were felt to be unusual and an external opinion was sought in the Bethesda Medical Center in the USA and the correspondence expressed that the sample tested presented evidence of infarction and inflammation but that given the size of the splenic lesion, it would not be representative. On the basis of these results and persistent concern for lymphoma, the need for an elective splenectomy was suggested.

Outcome and follow-up

The case was discussed at a sarcoma multidisciplinary meeting where the consensus was for elective splenectomy. Prior to the procedure, it was arranged for the patient to receive the 13-valent conjugate pneumococcal vaccine (Prevnar), the MenACWY vaccine and hemophilus B vaccine.

On 2 November 2017, the patient underwent an open splenectomy with a midline laparotomy incision, closure with 2.0 polydioxanone suture and clips to the skin. A PICO single use negative pressure wound therapy dressing was applied to the wound and no intraoperative nor postoperative complications were documented. Two specimens were sent to the laboratory: an omental biopsy and the spleen (figure 4). The omental biopsy was reported to be benign omental tissue, negative for malignancy.

The spleen measured 18×11×6 cm and weighted 444.6 grams, revealing an 8×5.2×5.3 cm multinodular tumour. The background parenchyma was unremarkable. The microscopic report of the spleen showed a multinodular vascular proliferation composed of vascular channels of variable calibre lined by plump endothelial cells with intervening bland ovoid cells and fibro-hyaline stroma. Interspersed red blood cells and mononuclear inflammatory cells were present but there was no evidence of significant nuclear atypia, mitoses or necrosis and lymphoma.

The histologic findings were consistent with a benign vascular neoplasm with the overall constellation of morphologic and immunohistochemical features favouring sclerosing angiomatoid nodular transformation.