Finding a needle in the haystack: A hidden follicular lymphoma

The classical morphological features of follicular lymphoma (FL) are well-recognized. However, identifying some morphological variants, such as FL with hyaline-vascular Castleman disease (HVCD) like features (FL-HVCD), is challenging. Hence, we report a 57-year-old male with FL-HVCD who presented with nontender swelling of the bilateral lower limbs, caused by enlarged intra-abdominal lymph nodes with venous compression. The excised lymph nodes showed onionskin-like mantle zones and hyalinized blood vessels, which was consisted with HVCD. Oral medications were prescribed; however, the patient was lost to follow-up after 6 months and was readmitted with anemia, thrombocytopenia, and leukocytosis 3 years later. A bone marrow biopsy was done, and the patient was diagnosed as having overt FL with bone marrow involvement. Physicians should be careful if HCVD patients present with systemic symptoms or generalized lymphadenopathy. Excluding the possibility of lymphoma is necessary because the different treatment strategy and prognosis from HVCD.