A 61-year-old man was admitted to hospital with collapse having had a 6-week history of a rapidly enlarging neck mass. On examination there was a large mass that appeared to arise from the thyroid but no palpable lymphadenopathy. An electrocardiogram showed sinus bradycardia, with a rate less than 40 beats per minute (the rhythm strip lead II is shown, top) and symptomatic pauses were captured on a cardiac monitor. The patient had a recurrent episode of collapse in hospital and a diagnosis of carotid body infiltration with vagal nerve stimulation leading to bradyarrythmias was made. The patient had no prior cardiac medical history. Thyroid-stimulating hormone was 10·5 mIU/L (normal range 0·35–4·00) and free thyroxine (T4) was 11·4 pmol/L (normal range 11–24), which represents subclinical hypothyroidism but not thought to be causing the bradycardia, however levothyroxine 100 μg daily was commenced. The patient was treated with an intravenous isoprenaline infusion followed by an emergency implantation of a permanent pacemaker after which he had no more episodes of collapse and remained haemodynamically stable with a normal pulse. A biopsy from the mass showed diffuse large B-cell lymphoma and staging computed tomography (slices from the neck are shown) showed the disease was localized to the neck (Stage IE). He was started on R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone) chemotherapy and the neck mass rapidly resolved; he continues currently on treatment.
Previous reports have described lymphoma with direct involvement of the heart, mediastinum and carotid body that have caused heart block requiring cardiac pacing. The presumed mechanism of bradyarrythmia in this case is vaso-vagal stimulation caused by carotid body baroreceptor compression. This case highlights a rare complication of lymphoma occurring in the neck that is treatable once it has been recognized.