Diffuse large B cell lymphoma of thyroid as a masquerader of anaplastic carcinoma of thyroid, diagnosed by FNA: a case report

BACKGROUND: Both thyroid lymphoma and anaplastic carcinoma of thyroid present with rapidly growing mass in eldery patients. Anaplastic carcinoma has high mortality rate and combination of surgery, radiation therapy and multidrug chemotherapy are the best chance for cure. Prognosis of thyroid lymphoma is excellent and chemotherapy for widespred lymphoms and radiotherapy with or without adjuvant chemotherapy for tumors localized to the gland, are the treatment of choice. CASE REPORT: This article reports a 70 year old man presenting with diffuse neck swelling and hoarseness of few weeks duration. Fine needle aspiration was done and reported as anaplastic carcinoma of thyroid which thyroidectomy was planned. The slides were sent for second opinion. After review, with initial diagnosis of anaplastic carcinoma versus lymphoma, immunocytochemical study was performed. Smears were positive for B cell markers and negative for cytokeratin, so with the impression of diffuse large B cell lymphoma, the patient received two courses of chemotherapy by which the tumor disappeared during two weaks. CONCLUSION: Despite previous reports, stating easy diagnosis of high-grade thyroid lymphoma on the grounds of cytomorphological features we like to emphasize, overlapping cytologic features of the curable high grade thyroid lymphoma form noncurable anaplastic thyroid carcinoma and usefulness of immunocytochemistry to differentiate these two disease.