Post-Chemotherapy Histiocyte-Rich Pseudotumors: Radiologic and Endoscopic Mimics of Residual Lymphoma.

Development of post-chemotherapy histiocyte-rich pseudotumor (PHP) is an underrecognized event following therapy in lymphoma patients and may mimic residual tumor using current therapy monitoring protocols. We report a series of 5 patients with PHP along with a review of the literature. In our series, we describe 3 patients with persistent hypermetabolic masses by positron emission tomography-computed tomography, one with persistent terminal ileal nodules on endoscopy, and one with bone marrow involvement, a site not associated with mass-like disease. Twenty-three patients with long-term follow-up were identified from our series and review of the literature. Forty-four percent of patients received additional therapy, and only 4% of patients died of lymphoma. This study illustrates that PHPs are not identified using current lymphoma therapy monitoring algorithms and may result in overtreatment with risk for additional therapy-related complications. The need for confirmatory tissue biopsy in this setting is recommended.