Case Author(s): Xia Wang, M.D. and Barry A. Siegel, M.D. , 07/27/05 . Rating: #D3, #Q3

Diagnosis: Mediastinal Large B-cell Lymphoma with Recurrent Laryngeal Nerve Compression

Brief history:

25-year-old man initially presented with shortness of breath, hoarseness and neck vein distention.


Coronal FDG-PET images. View MIP cine in AVI format.

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View second image(pt). Axial FDG-PET/CT images.

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Full history/Diagnosis is available below

Diagnosis: Mediastinal Large B-cell Lymphoma with Recurrent Laryngeal Nerve Compression

Full history:

25-year-old man initially presented with shortness of breath, hoarseness and neck vein distention. CT study performed at another hospital demonstrated a large anterior mediastinal mass. Subsequent biopsy was inconclusive. PET/CT study was requested for staging.


There is a large area of heterogeneously increased FDG uptake seen in the anterior and middle mediastinum, which corresponds to a bulky and conglomerate mediastinal mass with cystic components, extending from the level of aortic arch to the level of left hilum and displacing the trachea and great vessels posteriorly. This large mass has a maximum standardized uptake value of 7.5. The cystic components of this mass reveals absent FDG uptake, suggestive of tumor necrosis.

There is asymmetrically increased FDG uptake involving the right vocal cord with lack of FDG uptake within the left vocal cord. This is most likely secondary to left vocal cord paralysis from compression of the left recurrent laryngeal nerve by this bulky mass.

The CT portion of the examination demonstrates that the left vocal cord is collapsed and also shows a pericardial effusion.


The recurrent laryngeal nerve is derived as a branch of the vagus nerve, on the left side as it passes the arch of the aorta and on the right side as it passes the subclavian artery. Upon reaching the larynx, it becomes the left and the right inferior laryngeal nerve and it passes at the posterior aspect of the cricothyroid joint. With the exception of the cricothyroid muscle, the inferior laryngeal nerve supplies all the intrinsic muscles of the same side and the transverse arytenoid muscles bilaterally.

Symmetrically increased FDG uptake in the vocal cords and muscles of phonation is often seen in patients who talk during the FDG uptake phase of the examination; this is a normal variant, due to the increased glucose utilization of these active muscles. The finding of asymmetric FDG uptake in the laryngeal muscles warrants investigation, to determine if the side with increased activity harbors a tumor or if the side with relatively decreased uptake is a result of vocal cord paralysis secondary to a mass lesion along the course of the recurrent laryngeal nerve or as a result of injury during surgery (e.g., thyroidectomy) or radiation therapy.

The differential diagnosis of an anterior mediastinal mass includes thymic tumors, germ cell tumors, lymphoma (and other causes of lymphadenopathy), and thyroid masses.

Hodgkin’s lymphoma occurs with a bimodal age distribution, with peaks at 30 and 70 years. Radiographic features include superior mediastinal nodal involvement, contiguous progression from one lymph node group to next, 15% lung involvement, 15% pleural effusion.

Most (85 %) Non-Hodgkin’s lymphomas arise from B cells and the remainder (15%) arise from T cells. 60% originate in lymph nodes and 40% in extranodal sites. There is an increased incidence in patients with altered immune status, including patients post transplantation and those with AIDS, congenital immunodeficiency syndomes, and collagen vascular disease (RA, SLE). Radiographic features are generalized or noncontiguous mediastinal and hilar adenopathy, lung involvement, extrathoracic spread( nasopharynx, GI tract, spread to unusual sites).

Thymoma is the most common anterior mediastinal tumor in adults. 30% are invasive. 35% of patients have myasthenia gravis. Radiographic features include asymmetrical location on one side, homogenous density and signal intensity; some have cytic components and contrast enhancement. Invasive thymomas show growth beyond the capsule into adjacent tissues. Drop metastases into the pleural space are common. 20% presents with a calcified mass.

Multinodular goiter is the most common thyroid mass that extends into the mediastinum. Radiographic features include thoracic inlet masses, contiguous with the cervical thyroid gland, heterogenous density by CT, and marked and prolonged contrast enhancement on CT.

Germ cell tumors include seminoma, embryonal cell carcinoma, choriocarcinoma, teratoma and yolk sac tumor. 70% of germ cell tumors are teratomas. Teratoma typically presents as a large mass lesion with variable tissue contents (calcification, fat, fat-fluid levels, cystic areas, soft tissue).

View followup image(pt). Another PET/CT images to demonstrate the tumor.

Major teaching point(s):

It is not uncommon to see asymmetric increased FDG uptake in the vocal cords secondary to an extrinsic mass compressing the recurrent laryngeal nerve.

Differential Diagnosis List

1. Thymic masses (Thymoma, Thymic cyst, Thymolipoma) 2. Germ cell tumors (Seminoma, Embryonal cell carcinoma, Choriocarcinoma, Teratoma) 3. Lymphadnopathy( Lymphoma, sarcoid, tuberculosis) 4. Aneurysm and vascular abnormalities(involved both anterior and involve both the anterior and superior mediastinal compartments. 5. Thyroid lesions

ACR Codes and Keywords:

References and General Discussion of PET Tumor Imaging Studies (Anatomic field:Lung, Mediastinum, and Pleura, Category:Neoplasm, Neoplastic-like condition)

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Case number: pt139

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