Abdominal imagingCase Type
Dr. Nikita Sampathirao, Dr. Indirani Muthukrishnan, Dr. Pramukh Kulkarni, Dr. Jaykanth Amalchandran, Dr. Asra Ejaz Patel, Dr. Shelley SimonPatient
54 years, female
A 54-year-old lady, referred for FDG PET/CT, complained of chest discomfort, dyspnoea, cervical adenopathy, low-grade fever, polyarthralgia and epigastric pain. Routine lab investigations and serum lactate dehydrogenase were normal. She was seronegative for HIV and HHV. ESR and CRP were raised at 110 mm/hr and 38 units.
FDG PET with contrast CT scan from the vertex of the skull till toes was performed following an institutional protocol at 60 minutes after an intravenous injection of 7 mCi FDG. The maximum intensity projection image (MIP) (Fig 1) and the sectional analysis of the scan demonstrated multiple discrete intensely enhancing intraparotid, cervical, supraclavicular, mediastinal, hilar, axillary, abdominal and pelvic adenopathy (Fig 2) (with a maximum standardized uptake value, SUVmax of 5.0 in left intraparotid nodes. Additionally there was an evidence of splenomegaly (Fig 3 c,d), with the spleen measuring 14.5 cms and showing diffuse increased FDG uptake (SUVmax 4.0).
Liver was enlarged measuring 22 cms. Multiple foci of abnormal FDG uptake were noted in segments III and V (Fig 3 a,b). A curvilinear pattern of FDG uptake was seen along the segment VII of liver with no corresponding CT abnormality (SUVmax 7.1) which was suspicious for peritoneal deposits along the liver surface (Fig 4).
The bone marrow demonstrated homogenously increased FDG uptake suggestive of bone marrow hyperplasia. No significant metabolically active abnormality was seen elsewhere in the whole body.
Castleman’s disease (CD) is benign lymphoproliferative disorder that is similar to lymphoma . Aetiology of CD is unclear, the widely accepted hypothesis being chronic low-grade inflammation with interleukin-6 overproduction . CD affects lymphatics predominantly. It can be unicentric (one group of nodes) or multicentric (MCD), involving multiple nodes and rarely extranodal sites like lungs, larynx, parotid glands, pancreas and meninges [2-4]. Pathologically, MCD is associated with plasma cell variant .
Hepatic involvement in MCD is rare. There have been reports of primary hepatic involvement in CD previously, but as the unicentric variant . CT and MRI findings are characteristic in the evaluation of involved lymph nodes, but it is difficult to evaluate hepatic involvement .
CD being associated with inflammation is known to accumulate FDG and findings of FDG PET/CT are indistinguishable from lymphoma [2,8]. The definitive diagnosis is by histopathology. The overall impression, in this case, was in favour of lymphoma, due to the hepatic and suspicious peritoneal involvement. Excision biopsy of the cervical nodes revealed a diagnosis of Castleman's disease (plasma cell variant) with positive expression of CD3, CD20, C10, CD23 and CD 138 on immunohistochemistry.
Hepatomegaly is seen in CD, but parenchymal involvement does not occur commonly . However, MCD can produce atypical mixed cellular infiltrates in the liver . Strip pattern of enhancement on CT, adjacent to focal lesion has been observed in primary hepatic CD which was hypothesized due to lymphatic proliferation along the strip . The curvilinear pattern of FDG uptake in segment VII of liver with discrete ill-defined FDG avid foci turned the analyzing minds towards peritoneal disease which is seen in lymphoma, thus favouring lymphoma as primary imaging impression, which got disproved by histopathology. Curvilinear FDG uptake, in this case, could represent the lymphoproliferation in strip-like lesion. However, biopsy of liver lesions could not be performed.
CD, a great mimic of lymphoma, is a potential differential on FDG PET/CT. SUVmax has been used to differentiate between these two entities , but high uptake has been noted in both . The MIP image of FDG PET/CT in both lymphoma and CD can be regarded as mirroring each other, thus resulting in ‘SCAN MIRRORING’. FDG PET/CT is of little help in differentiating between two but is of great importance for distinguishing between unicentric and multicentric disease and also delineating the extent. It can help guide management, response to treatment and prognostification.
Written informed patient consent for publication has been obtained.
CD: Castleman's disease
MCD: Multicentric Castleman's disease
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