6781 A Rare Case of Diffuse Large B Cell Lymphoma of the Thyroid

Abstract Disclosure: D. Deyar: None. M. Herrera: None. M. Ahmad: None. P. Ucciferro: None. Introduction: Primary thyroid lymphoma (PTL) is rare, comprising less than 5% of thyroid cancers. It is frequently seen in middle-aged women and 1.5% of patients with Hashimoto’s thyroiditis. PTL may present with rapidly growing mass, dysphagia, stridor, or hoarseness. We describe a case of a female patient presenting with a neck mass and new onset hypothyroidism who was found to have DLBCL of the thyroid. We aim to raise clinical awareness regarding PTL and elucidate its association with Hashimoto’s disease and discuss treatment strategies. Case presentation: The patient was a 62-year-old female with a past medical history of type 2 diabetes, hypertension, and hyperlipidemia, presenting for worsening neck swelling for the past four weeks. She reported tenderness around the mass along with voice hoarseness and difficulty swallowing. She also reported increased shortness of breath associated with the mass while lying flat and denied any heat intolerance, cold intolerance, weight changes or bowel habit changes. The patient’s vitals were as follows: blood pressure: 146/104 mmHg, heart rate: 58 beats per minute, temperature: 36.3 C, respiratory rate: 20 breaths per minute. Initial blood work demonstrated the following: sodium: 137 mmol/L, potassium: 4.2 mmol/L, 9.4 mg/dL, white blood cell count: 12.1 × 109/L, hemoglobin: 14.5 g/dL, platelets: 330 × 109/L, thyroid stimulating hormone: 17.1 uIU/mL, free T4: 0.4 ng/dL, and TPO antibodies: 300 IU/mL. A CT scan of her neck demonstrated a left sided mass measuring 6.6 cm, by 5.6 cm, by 11 cm. The patient was started on 50 mcg of levothyroxine and was assessed by otorhinolaryngology and underwent fine needle aspiration biopsy. The patient’s biopsy demonstrated diffuse large B cell lymphoma of the thyroid gland. The patient was started on R-CHOP chemotherapy for her lymphoma as an outpatient and had a significant decrease in the size of her neck mass and improvement in her compressive symptoms. She is scheduled for six cycles of R-CHOP therapy and continues to follow with oncology. Discussion: Diffuse Large B Cell Lymphoma (DLBCL) of the thyroid is rare and necessitates distinct therapeutic considerations. Patients with Hashimoto's thyroiditis have been found to be 60-fold times more likely to develop primary thyroid lymphoma as compared to those without thyroiditis. The pathophysiology regarding this association remains unclear, however some suggest it may be due to chronic lymphocytic inflammation of the thyroid gland leading to monoclonal lymphocyte growth. Treatment of DLBCL of the thyroid requires immunotherapy, most commonly with the R-CHOP therapy which distinguishes it from the conventional management of thyroid carcinomas. Physicians should be vigilant in considering these treatment differences and to consider PTL as an etiology of growing thyroid mass in patients with Hashimoto’s thyroiditis. Presentation: 6/2/2024