Description 

A 65-year-old woman, with a known case of Hashimoto’s thyroiditis on eltroxin for 15 years, presented with progressive diffuse swelling neck for 2 months. She also gave a history of difficulty in swallowing and breathing for 1 week. On examination, she had respiratory distress, low oxygen saturation (85% on pulse oximeter) and cyanosed tongue. Systemic examination was unremarkable except for goitre (grade 2) and stridor. As the saturation was not improving with supplemental oxygen, she underwent an emergency tracheostomy. Subsequently, a contrast-enhanced CT scan of the neck showed large lobulated heterogeneously enhancing lesion in the region of thyroid gland encasing all major structure of neck including trachea (figure 1). Core biopsy and immunohistochemistry (CD45, CD20, CD10 and BCL6 positive) confirmed the diagnosis as diffuse large B cell lymphoma (DLBCL). The patient received R-CHOP chemotherapy (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone). After 1 month, she was asymptomatic with >50% decreased swelling, and the tracheostomy tube was removed.

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Figure 1

(A) CT neck image showing a homogenous mass encasing the trachea (doughnut sign) and invading the common carotid artery and the tracheo-oesophageal groove. (B) CT neck image showing tracheostomy tube.

Hashimoto’s (autoimmune) thyroiditis is a known risk factor for thyroid lymphoma, making patients 60 times more prone to lymphoma than the general population.1 Primary thyroid lymphoma constitutes 1%–5% of thyroid malignancies. The majority (60%–80%) of thyroid lymphomas are DLBCL.2 On CT images, lymphoma can present with solid nodules, multiple nodules and diffuse swelling. In rare cases, it can present with the classical finding of ‘doughnut sign’ in which lymphoma completely encircle the trachea as in the index case.3