Reliability of cytopathology and ancillary testing modalities in the diagnosis of extramedullary hematopoiesis and sclerosing extramedullary hematopoietic tumor: a 10-year institutional experience.

Abstract

Introduction: Extramedullary hematopoiesis (EMH) is proliferation of hematopoietic elements outside of bone marrow that's commonly associated with hematologic diseases. While sclerosing EMH (SEMHT) has overlapping clinical features with EMH, it is less cellular and has solid appearance with fibrosis and atypical megakaryocytes. EMH/SEMHT are uncommon manifestations rarely reported in cytology. This study aims to investigate the reliability and utility of cytology in diagnosis of EMH/SEMHT in cytology samples at our institution.

Materials and methods: The laboratory information system was queried over a 10-year period (2014-2024) to identify all cytology cases diagnosed on fluid cytology, fine-needle aspiration (FNA), and/or small-core biopsy with Touch preparations as EMH and/or SEMHT. History of hematopoietic disorders, specimen location, type, diagnosis, ancillary studies, and follow-up data were reviewed and correlated.

Results: A total of 11 cases from 11 patients were identified. Age ranged from 57 to 84 years, and the male:female ratio was 0.8:1. History of transplant was noted in 3 patients, and hematopoietic disorders (1-myelodysplastic syndrome, 3-primary myelofibrosis, 1-chronic myeloid leukemia, 1-essential thrombocytosis) in 6 patients. Specimen origins were distributed as:1 peritoneal fluid, 2 pleural fluids, 8 soft tissue (4-paraspinal, 1-presacral, 1-peritoneal, 1-perigastric, 1-periportal lymph-node). This corresponded to 3 fluid cytology, 5 FNAs, and 3 core biopsies/Touch preparation. Five cases were diagnosed as atypical compatible with EMH, and 6 cases were diagnosed as negative for malignant cells with trilineage hematopoiesis compatible with EMH (5) and SEMHT (1). Flow cytometry was performed on 5 cases, while immunohistochemistry was performed on 6 cases, with both ancillary studies confirming the diagnosis of EHM/SEMHT in 9 of 11 cases (82%).

Conclusions: Cytology can provide reliable and accurate method for diagnosing EMH/SEMHT. EMH is less commonly encountered in effusions (27.3%). Ancillary studies, including flow cytometry and immunohistochemistry, are reliable techniques that aid in diagnosis EMH/SEMHT in various cytology samples.