To explore the differences in the clinical, ultrasound, and pathological features between primary thyroid lymphoma (PTL) and anaplastic thyroid carcinoma (ATC) to improve their diagnosis.

A total of 41 patients with PTL confirmed by surgical pathology or biopsy from January 2008 to August 2017 were selected. Among them, there were 11 males and 30 females, aged from 28 to 81 years old, with an average age of (60.8±12.5) years. In addition, 16 patients with ATC confirmed by surgical pathology were selected. Among them, there were 7 males and 9 females, aged between 18 and 88 years, with an average age of (65.1±15.1) years. The clinical, ultrasonic, and pathological findings of the two groups were analyzed retrospectively. Age and maximum diameter of the lesion were compared between the two groups using the two independent samples t-test. Clinical data including gender, short-term enlargement of neck mass, dysphagia, dyspnea, hoarseness, and distant metastasis, and ultrasonographic findings including border, margin, echogenicity, strip-like or grid-like hyperechoism, calcification, cystic degeneration, enhancement of posterior echo, blood flow, and cervical lymph node enlargement were compared using the 2 test and Fisher exact probability method. The diagnostic efficacy of ultrasonic characteristics was evaluated by ROC curve analysis.

The incidence of hoarseness and distant metastasis was significantly lower in patients with PTL than in those with ATC (P<0.05). There was no statistically significant difference between the two groups in terms of age, gender, rapid enlargement of neck mass, dyspnea, or dysphagia (P >0.05). Compared with the ATC group, marked hypoechogenicity, strip-like or grid-like hyperechogenicity, and enhancement of posterior echo were significantly more common, and calcification and cystic changes were significantly less common in the PTL group (P<0.05). There was no statistically significant difference between the two groups in lesion size, boundary, margin, or cervical lymph node enlargement (P>0.05). ROC curve analysis showed that the sensitivities of marked hypoechogenicity, strip-like or gridlike hyperechogenicity, enhancement of posterior echo, absence of calcification, and absence of cystic changes were 61.7%, 74.5%, 89.4%, 100%, and 100%, the specificities were 81.0%, 81.0%, 100%, 57.1%, and 33.3%, and the areas under the curves were 0.713, 0.777, 0.947, 0.786, and 0.677, respectively. PTL exhibited monoclonal proliferation, the size and shape of tumor cells were more consistent, and there was more interstitial fibrosis. ATC had obvious structure and cell atypia, and the size of cancer cells was heterogeneous, and different degrees of tumor necrosis might occur.

The clinical manifestations of PTL and ATC are similar, but their pathological features are significantly different. Sonographic features such as marked hypoechogenicity, homogeneity echo texture, strip like or grid like hyperechogenicity, enhancement of posterior echo, lack of calcification and cystic changes, and complication with Hashimoto thyroiditis are of important value in differentiating PTL and ATC.