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. 2019 Jan;17(1):512-518.
doi: 10.3892/etm.2018.6948. Epub 2018 Nov 9.

Comparative study of computed tomography of normal and lymphoid follicular hyperplasia thymus in myasthenia gravis patients

Hui Zhang  1 , Peng Zhang  1 , Tie-Lian Yu  2
Affiliations

Comparative study of computed tomography of normal and lymphoid follicular hyperplasia thymus in myasthenia gravis patients

Hui Zhang et al. Exp Ther Med. 2019 Jan.

Abstract

The aim of the present study was to evaluate the thymuses of non-thymomatous myasthenia gravis (MG) patients by computed tomography (CT) for differentiating lymphoid follicular hyperplasia (LFH) thymus from normal/involuted thymus in order to assist surgeons in determining whether a non-thymomatous MG patient requires an operation. In the present retrospective review over 10 years, 80 patients who received CT scan and thymectomy at the Affiliated General Hospital of Tianjin Medial University (Tianjin, China) were included. According to the pathological records, 54 of the cases initially detected on CT were confirmed as LFH thymus. Thymic measurements, including anteroposterior and transverse dimensions, width (the longest axis of the lobe on a transverse scan) and thickness (the largest dimension perpendicular to the long axis of the lobe) and CT attenuation of the thymus region, adipose tissue and chest wall musculature in each CT slice were included to assess differences between the LFH group and the normal/involuted thymus group. Although a negative association between patient age and the CT attenuation of the thymus region was identified (r=-0.779, P<0.05, Pearson's correlation test), the LFH thymus group featured nodular changes on CT, while no such changes were observed in the normal/involuted thymus group. The mean age of disease onset in the LFH thymus group was significantly lower than that in the normal thymus group (40.2±17.3 vs. 59.2±9.3 years). Furthermore, significant differences in CT attenuation were identified between the LFH group and the normal/involuted thymus group [-41.21±54.42 vs. -108.23±8.72 Hounsfield units (HU) on unenhanced CT; -25.57±58.65 vs.-117.40±6.22 HU on contrast-enhanced CT]. In the LFH group, the difference in mean CT attenuation between the thymus region and adipose tissue was significant, while no significant difference was observed in the normal/involuted thymus group. In conclusion, CT may be used to distinguish LFH thymus from normal/involuted thymus in MG patients.

Keywords: computed tomography; involuted thymus; lymphoid follicular hyperplasia; myasthenia gravis; thymectomy; thymus gland.

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Figures

Figure 1.
Figure 1.
Correlation of the thymus CT attenuation with the age of the patients (r=−0.779; P<0.05). CT, computed tomography.
Figure 2.
Figure 2.
Unenhanced computed tomography image of a male myasthenia gravis patient (age, 18 years) with lymphoid follicular hyperplasia. The thymus is triangular in shape and may be easily distinguished from adjacent tissue.
Figure 3.
Figure 3.
Female myasthenia gravis patient (age, 26 years) with lymphoid follicular hyperplasia. The septum between the two lobes is visible.
Figure 4.
Figure 4.
Female myasthenia gravis patient (age, 36 years) with lymphoid follicular hyperplasia. The thymus is quadrilateral and the computed tomography attenuation in the thymus region is different from that of the adipose tissue and musculature.
Figure 5.
Figure 5.
Female myasthenia gravis patient (age, 45 years) with lymphoid follicular hyperplasia. The thymus is quadrilateral in shape and nodules are visible in the fat-infiltrated thymus region.
Figure 6.
Figure 6.
Contrast-enhanced computed tomography image of a female myasthenia gravis patient (age, 50 years) with lymphoid follicular hyperplasia. The thymus is triangular in shape and can be easily distinguished from adjacent tissue, particularly adipose tissue.
Figure 7.
Figure 7.
Female myasthenia gravis patient (age, 54 years) with LFH. The thymus is triangular in shape and a nodule is apparent, which was later pathologically confirmed as LFH. LFH, lymphoid follicular hyperplasia.
Figure 8.
Figure 8.
Contrast-enhanced computed tomography image of a female myasthenia gravis patient (age, 58 years) with lymphoid follicular hyperplasia. The thymus is triangular in shape and nodules are apparent in the thymus region.
Figure 9.
Figure 9.
Unenhanced computed tomography image of a male patient (age, 67 years) with myasthenia gravis and lymphoid follicular hyperplasia. The thymus is quadrilateral in shape and certain nodules may be distinguished from adipose tissue.
Figure 10.
Figure 10.
Contrast-enhanced CT image of a male myasthenia gravis patient (age, 43 years) with normal thymus. The thymus is quadrilateral in shape and homogeneous regarding CT attenuation. CT, computed tomography.
Figure 11.
Figure 11.
Unenhanced CT image of a male myasthenia gravis patient (age, 59 years) with normal (involuted) thymus. The thymus is quadrilateral in shape and homogeneous regarding CT attenuation. CT, computed tomography.
Figure 12.
Figure 12.
Unenhanced CT image of a male myasthenia gravis patient (age, 72 years) with normal thymus. The thymus is quadrilateral in shape and homogeneous regarding CT attenuation. CT, computed tomography.
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