# Pleural Effusion in a Patient With Chronic Myelomonocytic Leukemia Treated With Azacitidine

## TL;DR

A patient with chronic myelomonocytic leukemia developed pleural effusion, highlighting the need for careful monitoring in similar cases.

## Contribution

This case report highlights the under-recognized occurrence of pleural effusion in CMML patients.

## Key findings

- Pleural effusion was found in a CMML patient after chemotherapy.
- Cytology showed reactive cells but no malignancy.
- Leukemic pleural effusions in CMML may be underdiagnosed.

## Abstract

Pleural effusion is an uncommon occurrence in chronic myelomonocytic leukemia (CMML) patients, and its mechanisms remain poorly understood. We report the case of a 66-year-old male with a known medical history of CMML, referred from the oncology clinic due to shortness of breath attributed to a left pleural effusion, evident on a chest X-ray following a chemotherapy session. A diagnostic thoracentesis and cytology were conducted, which yielded exudative fluid negative for malignant cells and found reactive mesothelial cells and macrophages in a background of numerous chronic inflammatory cells and acellular proteinaceous material. However, due to the limited effectiveness of cytological examination in identifying malignant pleural effusions, the occurrence of leukemic effusions in CMML patients may be underestimated. This case underscores the importance of prompt recognition and management of pleural effusion in patients with underlying hematologic conditions like CMML.