Table 2.

Clinical, radiological, and histological differences between primary thyroid lymphoma, undifferentiated thyroid carcinoma, and Rosai Dorfman disease

	Primary thyroid lymphoma (PTL)	Undifferentiated thyroid carcinoma	Rosai Dorfman disease (RDD)
Clinical presentation	Rapidly enlarging neck mass History of lymphocytic thyroiditis ~ 10-12% have compressive symptoms (dyspnea, hoarseness, stridor) and/or B-symptoms (fever, weight loss, night sweats) Firm and smooth lesion on physical examination [18]	Rapidly enlarging neck mass Frequent compressive symptoms Older age (>50) Extrathyroidal extension and local organ invasion [19]	Nodal form Massive bilateral lymphadenopathy (often cervical) that is painless May present with B-symptoms Additional lymph node involvement common (inguinal, axillary) Extranodal form Head and neck location can present with local mass effect, including respiratory symptoms [22] Younger age at presentation (mean ~20 years old) [23]
Radiology	Ultrasound Nodular, diffuse, or mixed type with enhanced posterior echoes [18] Computed topography Homogenous attenuation without necrosis or calcification	Ultrasound Solid, irregular, hypoechoic, internal calcifications and lymph node involvement [20] Computed topography Solid, ill-defined border, internal calcification, necrosis, and heterogenous attenuation Local organ invasion frequent [19]	Ultrasound Focal hypoechoic or mixed echogenic nodule (similar to thyroid carcinoma) Diffusely enlarged, heterogeneously hypoechoic echotexture (similar to thyroiditis) [23] Computed topography isolated or diffuse lymphadenopathy with enhancement, infiltrative appearance if in organ [23]
Pathology	Most common subtypes: DLBCL, Mucosa-associated lymphoid tissue (MALT), follicular, small lymphocytic, and Hodgkin’s lymphoma DLBCL: Diffuse infiltrate of medium to large atypical lymphoid cells with B-cell markers as shown in Table 1 [18]	Spectrum of spindle cell, giant cell, and squamoid Hypercellularity with widespread invasion, angiotropism, and necrosis Large pleomorphic cells with frequent bizarre nuclei and prominent nucleoli [21]	Emperipolesis is characteristic within histiocytes containing abundant cytoplasm (clear, eosinophilic) Background inflammation by lymphocytes and plasma cells Sinus histiocytosis in lymph nodes Immunohistochemistry: S100(+), CD68(+), CD1a(−), Factor XIIIa(−) [23]