P-66 Primary Thyroid Lymphoma mimicking Riedel Thyroiditis
Authors: Kocaman Banu Betül , Şahin Serdar , Uysal Serhat , Muradov Ilkin , Soltanova Lala , Kara Zehra , Çapar Mehmet Umut , Gönen Mustafa Sait 
Published: January 2024

Abstract

Introduction
Although Riedel's thyroiditis and primary thyroid lymphoma are rare diseases of the thyroid, they should be considered in the differential diagnosis of patients presenting with a neck mass. We report here the case who was followed up with the diagnosis of Riedel's thyroiditis and later diagnosed with lymphoma.

Clinical Case
A 67-year-old female presented with swelling in the neck, pain and shortness of breath. Thyroid ultrasound demonstrated enlarged thyroid gland, heterogeneous parenchyma, irregular contours, thin septations and pseudonodule formations. Laboratory tests revealed, TSH 4.17 mIU/L, fT4 1.37 ng/dl, anti TPO 147 IU/mL, sedimentation 13mm/h, and CRP of 5.5 mg/dl. In neck CT, an 8*4 cm hypodense mass infiltrating both thyroid lobes, extending anteriorly and superiorly, surrounding the trachea by 270 degrees, was detected. Follicle cells were seen in the fine needle aspiration biopsy, but no neoplasm was found. In PET-CT, increased FDG uptake was detected in the thyroid parenchyma (SUVmax: 22.89) and in one subcentimetric lymph node (SUVmax: 3.5) in the right cervical region. No neoplasm was found in the tru-cut biopsy and the biopsy was reported as granulomatous thyroiditis. When her current complaints and physical examination findings were evaluated together, methylprednisolone was started, considering Riedel's thyroiditis. In the follow-up examination, the thyroid size of the patient decreased significantly and the steroid dose was reduced. The patient, who could not be followed up for a while, developed swelling and pain in the neck again, and was followed up in the ICU with acute respiratory failure, a tracheal stent was applied to the patient. The patient was then followed in the ward, with dyspnea, dysphagia and hoarseness continued, was admitted to our polyclinic again and was hospitalized. The patient stated that her oral intake decreased due to dysphagia and there was a loss of 40 kg. She had no fever or night sweats. She was not smoking. Physical examination revealed a hard, fixed mass that completely filled the right neck and reached the midline. In the endoscopic examination, the vocal cords were paralytic, the air passage was inadequate, and the mass was invading the trachea. Tracheostomy was applied to the patient. Trucut biopsy was taken from the thyroid tissue. In addition, PET-CT was taken. On PET-CT, right thyroid dimensions showed significant morphological progression compared to the previous study, very dense at similar levels (previous SUVmax: 22.89,current SUVmax: 22.76);intense FDG uptake was detected in 8 mm lymph nodes in the left cervical and 19×20 mm lymph nodes in the right supraclavicular (SUVmax 22.17) region.Diffuse Large B-Cell Lymphoma was detected as a result of thyroid biopsy and R-CHOP treatment was started on the patient. She was discharged after 2 cycles of chemotherapy (Figure).
The diagnosis of both Riedel's thyroiditis and primary thyroid lymphoma are histopathological. The importance of open surgical biopsy and cooperation with an endocrine-specific pathologist was emphasized through our case.Figure.Photos of the patient at her initial and last state