Splenic Epstein–Barr virus-positive inflammatory follicular dendritic cell sarcoma

A 66-year-old female underwent an abdominal computed tomography (CT) scan following the incidental detection of two hepatic nodules during an ultrasound performed for unrelated indications. At the time of presentation, she was asymptomatic and had no relevant medical history. The CT scan confirmed hepatic haemangiomas but revealed an unexpected splenic mass.

The abdominal CT scan (Figures 1a, 1b, 1c and 1d) revealed a splenic mass measuring approximately 6 cm. The mass was isodense on non-contrast CT. After contrast administration, the mass exhibited progressive and sustained enhancement with early peripheral “capsule-like” enhancement, with some hypoenhancing central areas.

An abdominal magnetic resonance (MR) was performed for further lesion characterisation (Figures 2a, 2b, 2c, 2d, 2e, 2f and 2g). The splenic mass appeared heterogeneous, predominantly T2 isointense to hypointense and T1 isointense, with a T2-bright non-enhancing central scar. After gadolinium administration, the mass demonstrated progressive enhancement with no washout.

Given its size and the diagnostic uncertainty, a splenectomy was performed. Histopathological and immunohistochemical analysis (Figures 3, 4a, 4b, 4c, 4d and 4e) revealed inflammatory pseudotumor-like follicular dendritic cell sarcoma, positive for Epstein–Barr virus (EBV).

Background

Follicular dendritic cell sarcoma (FDCS) is a rare neoplasm arising from follicular dendritic cells typically found in lymph nodes [1,2]. Extranodal FDCS can occur in various organs, including the tonsils, nasopharynx, gastrointestinal tract, and retroperitoneum [1,2]. The Epstein–Barr virus-positive inflammatory follicular dendritic cell sarcoma (EBV+ iFDCS), a distinct entity, is even rarer, with fewer than 150 cases documented in the literature [2–4]. EBV+ iFDCS is predominantly found in young to middle-aged women with EBV positivity and primarily affects the liver or spleen [2,3].

Clinical Perspective

FDCS, especially EBV+ iFDCS, is often asymptomatic or presents with non-specific symptoms, such as abdominal distension, abdominal pain, and anaemia [1–3]. In this case, the mass was incidentally detected during imaging performed for unrelated reasons. Clinical suspicion of a malignant lesion was raised due to the size of the splenic mass and its non-reassuring imaging features.

Imaging Perspective

Although imaging is usually insufficient to definitely diagnose EBV+ iFDCS, certain features have been described that may suggest this diagnosis. CT imaging typically reveals a large, well-circumscribed, heterogeneous, isodense mass with progressive and sustained enhancement following contrast administration [3,5]. The “capsule-like” enhancement at the periphery of the mass is considered characteristic, and calcifications may be present [3,5]. On MR, lesions are typically T1 isointense to hypointense with heterogeneous signal intensity on T2 sequences, often displaying a central stellate low-signal-intensity scar [5]. Delayed enhancement following gadolinium administration is also common, likely due to the fibrous stroma [3,5].

Outcome

EBV+ iFDCS is considered an indolent malignant tumour with a generally better prognosis than classic FDCS, although long-term follow-up is necessary due to the potential risk of recurrence [1–3]. Our patient had a favourable outcome, with no recurrence.

Teaching Points

• EBV+ iFDCS is a rare, often indolent, variant of FDCS that can mimic benign splenic lesions on imaging.
• Large or atypical splenic masses require histopathological and immunohistochemical confirmation to rule out malignancy.
• Splenectomy serves as both a diagnostic and therapeutic intervention for such cases.