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Two cases of Primary thyroid lymphoma in hypothyroid patients presenting as goitres

Razak Kehinde, Ana Pokrajac, Chantal Kong, West Hertfordshire NHS Trust

The first case is of a 79-year-old woman who presented with a rapidly enlarging goitre and shoulder discomfort in March 2017. PMH hypothyroidism. Examination revealed a hard, large mass on in the anterior aspect of the neck expanding to the Right shoulder. It was not mobile on swallowing. USS revealed a complex fleshy solid right sided mass with retrosternal extension (U4). FNA cytology showed a high-grade lymphoma with lymphoid cells positive for CD20, BCL6 and PAX5. Few CD3 and CD5 positive T cells were noted. Calcitonin, MNF116, Thyroglobulin, TTF1 and cyclinD1 were negative. PET CT demonstrated an intensely avid uptake in the right thyroid.Core biopsy confirmed a diffuse large B cell lymphoma, Stage 1Ae localised disease. Excellent response to the 1^st cycle of chemotherapy with almost complete resolution of goitre when reviewed in clinic.  The chemotherapy and adjuvant radiotherapy were completed in September 2017 and an end of treatment PET CT is booked for mid-November 2017.

Second case is of a 52year old man with PMH hypothyroidism, with a recent 3 week history of an enlarging left neck swelling in late September 2017. Neck USS revealed a 39x36x23mm vascular mass occupying most of the left thyroid lobe with no evidence of microcalcification(U4). USS-guided FNA revealed lymphoid blasts with body macrophages and lymphoglandular bodies, indicative of a high grade B-cell non-Hodgkins lymphoma. Immunocytochemistry stains strongly positive for CD20, CD3. He was urgently seen in the haematology clinic and has been booked to have chemo-immunotherapy using a combination of Rituximab plus CHOP followed by radiotherapy.

Thyroid lumps are rarely caused by lymphoma (1% of cases) but the index of suspicion increases with hard, fixed masses that are rapidly growing. These cases also demonstrate the additional risk of lymphoma that could be present in hypothyroid patients, due to Chronic Lymphocytic thyroiditis (Relative risk 67)¹.

References:

1. Cancer risks in patients with chronic lymphocytic thyroiditis. N Engl J Med.  1985; 312(10):601-4 (ISSN: 0028-4793) Holm LE; Blomgren H; Löwhagen T