Cytological features of Castleman disease: a review

Castleman disease (CD) is a benign lymphoproliferative disorder with hyaline vascular (HVCD), plasma cell (PC-CD), and mixed subtypes. Only HVCD lymph node cytomorphology has been described, mainly as case reports. We reviewed all CD subtypes. To the best of our knowledge, our case series is the largest and most comprehensive yet published.

We searched our institution's database for histologically confirmed CD cytology cases (fine needle aspiration, touch preps) for the past 23 years. Two independent pathologists evaluated cytomorphology. We then reviewed touch preps from 6 histologically confirmed, non-CD reactive lymph node excisions.

8 patients (5 women, 3 men) had the following subtypes: HVCD (5 patients), PC-CD (2), and mixed (1). All cases had a heterogenous background population composed predominantly of small lymphocytes with single and clustered follicular dendritic cells (FDCs). The FDCs had delicate pale cytoplasm with indistinct borders showing lymphocyte emperipolesis. They were often binucleated or multinucleated with fine chromatin, regular nuclear borders, large nuclei, and small nucleoli. HVCD cases had traversing, frequently hyalinized capillaries. PC-CD cases had increased plasma cells, including binucleate forms, and tingible body macrophages with fewer FDC clusters. Human herpes virus-8 immunostain was negative in all cases. Non-specific follicular hyperplasia cases had abundant tingible body macrophages, rare hyalinized capillaries, and no lymphocyte emperipolesis.

CD is distinguished by background lymphocytes and cohesive FDC clusters with lymphocyte emperipolesis. HVCD has traversing, hyalinized capillaries and PC-CD has increased plasma cells and tingible body macrophages. Knowledge of these features can prevent a lymphoma misdiagnosis.