A young female presented to the accident and emergency department with incidental finding of a chest wall swelling. She was completely asymptomatic, and otherwise fit and well. She was a non-smoker and was not on prescribed medications. There was no family history of serious illnesses. Clinically, she looked well and not distressed. Systemic examination revealed a firm non-mobile painless skin mass in the upper right parasternal chest area measuring about 2x4 cm.

The rest of physical examination was unremarkable. A plain chest X-ray showed widened mediastinum, (Figure 1A). Computed tomography (CT) scan of thorax revealed an approximately 9x4 cm mass with irregular outline in the anterior mediastinum invading the vascular structures of the mediastinum and the anterior chest wall. It also showed a right-sided pleural effusion (Figure 1B). There was no evidence of neck lymphadenopathy, metastasis, interstitial changes or other lung lesions and the rest of the organs were normal. The superior vena cava was patent but flattened by the mass. Pericardial effusion was noted. Incisional biopsy of the mass and subsequent histological examination confirmed the diagnosis of high grade primary mediastinal B-cell lymphoma. She was started on urgent chemotherapy in the form of rituximab with prednisolone, fluconazole, and allopurinol. A repeat CT scan of thorax after six cycles of chemotherapy treatment revealed no convincing evidence of residual or recurrent lymphoma. The patient is in remission and under regular follow-up.

Primary mediastinal B-cell lymphoma (PMBL) comprises 7% diffuse large B-Cell lymphomas (2.4% of all non-Hodgkin lymphomas). The PMBL is a rapidly growing mediastinal tumor which arises in the thymus and is sometimes palpable in the supraclavicular area. Superior vena cava syndrome is common. Other presentations include phrenic nerve palsy, dysphagia and hoarseness. Shortness of breath can be due to pleural effusion or massive mediastinal mass. Our patient presented with incidental finding of a skin mass and subsequent investigations revealed the diagnosis of anterior mediastinal primary B-cell lymphoma that has invaded the anterior chest wall.

In this type of lymphomas, there is a female predominance and a median age at diagnosis in the third to fourth decade [1]. Patients present with a locally invasive anterior mediastinal mass originating in the thymus, with frequent airway compromise and superior vena cava syndrome [2]. Physical examination may show evidence of superior vena cava obstruction in the form of congested upper limbs and face. A mass could be palpable in the neck. Pleural effusion can be elicited clinically by dullness at lung bases with crepitations. The diagnosis of primary mediastinal large B-cell lymphoma is based on an evaluation of the tumor morphology and immunophenotyping interpreted in the context of the clinical presentation.

Patients with primary mediastinal B-cell lymphoma are often symptomatic due to compression of the superior vena cava or invasion of the lungs, pleura and even the pericardium. This case demonstrates how a young female patient was asymptomatic in spite of having advanced disease. The superior vena cava was flattened by the intrathoracic mass and there was a right-sided pleural effusion and pericardial effusion. The mass also invaded the anterior chest wall. In spite of all that, the patient presented with an incidental finding of a palpable skin mass, which is unusual of this type of tumor. It is important to realize that patients with primary B-cell lymphoma can have advanced disease without having typical symptoms at presentations.

1. Nguyen LN, Ha CS, Hess M, et al. The outcome of combined-modality treatments for stage I and II primary large B-cell lymphoma of the mediastinum. Int J Radiat Oncol Biol Phys 2000 Jul 15;47(5):1281–5.   [CrossRef]   [Pubmed]    
2. Van Besien K, Kelta M, Bahaguna P. Primary mediastinal B-cell lymphoma: A review of pathology and management. J Clin Oncol 2001 Mar 15;19(6):1855–64.   [Pubmed]