Unicentric Intra-abdominal Castleman’s disease mimicking malignancy

A 30-year-old female presented with insidious onset of right abdominal painless swelling for 2 years which was gradually increasing in size . On examination, a smooth, firm mass was palpated in the right lumbar region. Routine Lab investigations revealed anaemia (Hb 8gm/dL), however the remaining investigations were normal.

On ultrasound, a well defined solid mass lesion was seen in the right lumbar region. The lesion was having foci of coarse calcifications and  showing intense internal vascularity on Color Doppler.

On CECT, a large  well circumscribed, intraperitoneal soft tissue density lesion with multiple foci of coarse calcification, measuring 62 x 54 x 52 mm, seen in the right lumbar region. The lesion was showing intense homogenous enhancement on post contrast images. The fat planes with adjacent structures were maintained. Another similar characteristics lesion measuring 24 x 18 x 17 mm was seen adjacent to larger lesion. No evidence of retroperitoneal lymphadenopathy was noted. CECT of neck and thorax was done to look for multicentricity, which were normal.

Ultrasound guidance core biopsy of the mass was taken, which revealed lymph nodal tissue showing large number of plasma cells with hyalinized blood vessels. The lesion was positive for CD20, CD21 and CD138. A diagnosis of Castleman’s disease was made.

Background: Castleman Disease was first described by Dr Benjamin Castleman in a single case in 1954.^[1] It is a rare benign giant lymph node hyperplasia (also known as angiofollicular lymph node hyperplasia) characterised by atypical proliferation of lymphocytes. The cause of CD is unknown but it has been proposed that it is a response to chronic inflammation or a hamartoma of the lymphatic system and is associated with increase in serum interleukin-6 levels.^[2] CD is most commonly found in the mediastinum (67%), followed by neck (14%), abdomen and  pelvis (4%), and the axilla (2%). There are two subtypes of CD -Unicentric and multi-centric. Unicentric disease typically affects a younger age group (< 30 years) and tends to affect nodal groups above the diaphragm like the mediastinum. It responds well to surgical excision although some cases may need a combination of surgery and chemo-radiation. Multi-centric CD is associated with HIV and HHV8 coinfection. Patients frequently have systemic symptoms and associated polyclonal hyperglobulinemia, hypoalbuminemia, and raised ESR, CRP, IL-6.^[3] 15% have POEMS syndrome which consists of polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy and skin changes.^[4] The multicentric type requires systemic chemotherapy.^[5] There are two histological subtypes^[6]: the hyaline-vascular variant (accounts for approximately 90% of unicentric CD) and the plasma cell variant (seen in both unicentric and multicentric  CD).

Imaging perspective: Imaging of Castleman’s disease typically shows well-circumscribed masses of soft tissue attenuation. Calcification is infrequent and can include punctate, coarse, peripheral, and arborizing patterns.^[7,8] Smaller masses(<5 cm) show homogenous enhancement while larger masses (>5 cm)  are more heterogeneous in appearance with areas of necrosis.^[9] On MR imaging, nodes involved by CD are solid, have intermediate to slightly high signal T1WI and slightly hyper intense on T2-WI. Intralesional flow voids are seen on T1- and T2-weighted images reflecting the vascularity of the masses. Central linear hypo-intense septae maybe seen, thought to represent lamellar fibrosis.^[10]

Take home message CD should be considered in the differential diagnosis when a single persistently enlarged node or multistation lymphadenopathy is associated with high internal vascularity on color Doppler interrogation or moderate to intense post-contrast enhancement. Thus radiological imaging have a very important role in diagnosing CD. An excisional biopsy is preferred as a next step to differentiate it from lymphoproliferative disorders and other hypervascular masses.

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