# Behind the Swelling: Primary Mediastinal Large B-cell Lymphoma Masquerading as an Infection

## TL;DR

A young woman's lymphoma was initially mistaken for an infection, causing a delay in diagnosis.

## Contribution

Highlights the diagnostic challenge of primary mediastinal large B-cell lymphoma mimicking infection.

## Key findings

- Initial symptoms and imaging suggested pneumonia and cellulitis.
- Persistent symptoms and leukocytosis led to discovery of a mediastinal mass.
- Tissue analysis confirmed primary mediastinal large B-cell lymphoma.

## Abstract

We present the case of a 26-year-old female patient with a history of asthma who initially presented with symptoms suggestive of a common infection. Her constellation of facial swelling, productive cough, and fatigue, coupled with imaging findings, first led to a diagnosis of right upper lobe pneumonia and suspected cellulitis. Despite appropriate antibiotic therapy, her symptoms persisted, and her clinical picture became more complex with the identification of Actinomyces in her sputum, shifting the differential diagnosis toward a more indolent cervicofacial infection. However, a progressively worsening and profound leukocytosis, along with a lack of clinical improvement, prompted further investigation. This ultimately revealed a large mediastinal mass, and subsequent tissue analysis confirmed a diagnosis of primary mediastinal large B-cell lymphoma. This case highlights a critical diagnostic challenge, illustrating how a rare and aggressive malignancy can masquerade as a common infectious process in a young, otherwise healthy individual, leading to a significant delay in diagnosis and treatment.