Two Young Men with Mediastinal Masses

Abstract

Introduction The myeloid/lymphoid neoplasms with eosinophilia and gene rearrangement (MLN-Eos) are a rare group of hematopoietic neoplasms with diverse and often perplexing presentations that can cause challenges, and even potential pitfalls, for the diagnostic pathologist.1 The MLN-Eos demonstrate a male predominance, often strikingly so. While these MLN-Eos occur across a range of ages, the median age of onset is typically in the 40s, younger than in many other types of cancer, indicating that this is not a typical age-related cancer. Clinically these patients may show fatigue, pruritis, hepatosplenomegaly, and other protean symptomatology associated with eosinophilia, including restrictive pulmonary fibrosis, restrictive cardiomyopathy due to endomyocardial fibrosis, and eosinophilic gastritis or dermatitis as well as direct mass-forming symptoms. Often there is elevated tryptase and vitamin B12 associated with the granulocytic hyperplasia.