Thymus Of Patients Research Articles

Radiological changes in the thymus in patients who have had COVID-19 and in vaccinated persons who have not had COVID-19: a CT study.

There are very few and limited studies on the role of the thymus in COVID-19 infection. It is known that thymus morphology changes in individuals vaccinated against COVID-19 although they do not have active infection. Our study aims to evaluate these differences in detail. This research was conducted in atotal of 141 people, 75women and 66men. The research consisted of three groups: unvaccinated persons who have had the disease (n = 49), vaccinated persons who have not had the disease (n = 37), and unvaccinated persons who have not had the disease (control group, n = 55). In the study, the thymus volume, structure, and fat content were investigated and the differences between groups were evaluated. Thymus volume was greatest (0.43 ± 0.11) in the vaccinated group that had not had the disease and smallest (0.15 ± 0.07) in the unvaccinated group that had had the disease, and asignificant difference was found between the groups. Thymus steatosis was seen mostly in the unvaccinated group that had had the disease (72%; p = 0.04). The diffuse nodular pattern was only present in the diseased group. This research is the first study in the literature to date on the effect of COVID-19 and vaccines on the thymus. In addition to the acute consequences of the virus, the possibility of negative symptoms after COVID-19 should also be kept in mind, especially in unvaccinated people. Further studies are needed to confirm the results reported herein.

Silencing EPB41 Gene Expression Leads to Cell Cycle Arrest, Migration Inhibition, and Upregulation of Cell Surface Antigen in DC2.4 Cells.

BackgroundProtein 4.1R (EPB41) is the main cytoskeleton component of the erythrocyte membrane and may be involved in cell migration and adhesion. Previous research discovered overexpression of 4.1R in the thymus of patients with myasthenia gravis (MG). The protein 4.1R on dendritic cells may play a pivotal role in MG pathogenesis.This research investigated the effects of small interfering RNA 4.1R-siRNA on cell migration, cell cycle, and surface antigen expression of DC2.4 mouse dendritic cells, thus providing a new direction for the study of MG pathogenesis.Material/MethodsThree 4.1R-specific siRNAs were designed, and the expression of 4.1R was detected by real-time PCR at the mRNA level and Western blot analysis at the protein level to select out the most efficient siRNAs. Changes in cell morphology were observed and cell migration ability was analyzed by Transwell assay. Cell cycle and surface antigen were both analyzed by flow cytometry.ResultsThe cell bodies of DC2.4 diminished, the synapses were increased, and protuberance became more obvious after being transfected with 4.1R-siRNA. After knockdown of 4.1R, cell migration ability decreased and the proportion of cells in S phase significantly increased (both P<0.05). The expression levels of MHCII, CD80, and CD86 were all increased in DC2.4 cells (all <0.05).ConclusionsSilencing the expression of 4.1R in dendritic cells resulted in inhibition of migration ability, cell cycle arrest, and increase in surface antigens, which suggest that 4.1R participates in MG autoimmunity.

Detection of human parvovirus B19 infection in the thymus of patients with thymic hyperplasia-associated myasthenia gravis

ObjectiveTo investigate the association between myasthenia gravis (MG) and human parvovirus B19 (B19V) infection in the thymus. MethodsThe presence of human B19V DNA and protein was assessed in 138 samples—including 68 thymic hyperplasias (39 with MG), 58 thymomas (23 with MG), and 12 normal thymus tissues—using a nested polymerase chain reaction, immunohistochemistry, laser capture microdissection, and sequencing in a double-blinded manner. ResultsB19V DNA was detected mainly in thymic hyperplasia, and the positivity rate (41.18%, 28/68) was significantly higher than that in thymoma (3.45%, 2/58) (p <0.001) but not that in normal thymic tissues. Correspondingly, the positivity rate in thymic hyperplasia with MG (30.77%, 12/39) was significantly higher than that in thymoma with MG (4.35%, 1/23) (p=0.021). However, it was higher in thymic hyperplasia without MG (55.17%, 16/29) than in thymic hyperplasia with MG (30.77%, 12/39) (p=0.043). Cells in thymic hyperplasia positive for B19V VP1/VP2 protein (63.24%, 43/68) were identified mainly in ectopic germinal centres and thymic corpuscle epithelial cells, but were rare in thymomas (1.72%, 1/58) (p <0.001). Moreover, the positivity rate was significantly higher in thymic hyperplasia with MG (74.36%, 29/39) than in thymic hyperplasia without MG (48.28%, 14/29) (p=0.027). ConclusionsTo our knowledge, the present study is the first to show that human B19V infection is closely associated with thymic hyperplasia and thymic-hyperplasia-associated MG, but is not related to thymoma or thymoma-associated MG. The findings reveal a previously unrecognized aetiopathogenic mechanism of thymic-hyperplasia-associated MG, evoking numerous questions that require further investigation.

Thymus imaging in myasthenia gravis: The relevance in clinical practice.

The ability to distinguish between normal thymus, thymic hyperplasia, and thymoma should aid clinical management and decision making in patients with myasthenia gravis (MG). We sought to determine the accuracy of routine imaging in predicting thymic pathology. We retrospectively analyzed records of patients with MG from the Oxford Myasthenia Centre registry who had undergone thymectomy. Each patient received 1 radiological diagnosis and 1 histological diagnosis. We included 106 patients. Radiological and histological diagnoses agreed in 73 (68.9%) patients. Sensitivity and specificity, respectively, were calculated for each radiological diagnosis as follows: thymoma 90% and 95.5%, hyperplasia 17.6% and 98.6%, and normal 96.9% and 60.8%. Routine chest computed tomography and MRI can effectively identify thymoma. However, they are not reliable tools to differentiate between thymic hyperplasia and normal thymus in patients with MG. Muscle Nerve, 2018.

Thymic Involution After Radioiodine Therapy for Graves Disease: Relationships With Serum Thyroid Hormones and TRAb.

Context:The mechanisms of thymic hyperplasia in Graves disease and its involution after radioiodine (I-131) therapy remain unknown.Objective:To examine whether computed tomography (CT) findings of the thymus in patients with Graves disease change before and 6 months after I-131 therapy and to elucidate factors that affect these changes.Design, Setting:A retrospective, single-center study was conducted. Thymic and thyroid volumes and thymic density were measured on CT. The associations of thymic volume or density with the following factors before I-131 therapy were examined: age; serum triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone receptor antibody (TRAb) levels; and thyroid volume. The changes in thymic volume and density and TRAb levels before and after I-131 therapy, and the correlations of thymic volume with T3 and T4 decline rates and TRAb changing rate and age were examined.Patients:We studied 40 consecutive patients with Graves disease who underwent neck and chest CT before and 6 months after I-131 therapy.Intervention:Observational study.Results:A significant negative correlation was observed only between thymic density and age before I-131 therapy. Thymic volume and density decreased and TRAb levels increased significantly after I-131 therapy. The thymic volume decline rate significantly positively correlated with serum T3 and thyroid volume decline rates. No significant correlation was found between thymic volume decline and TRAb changing rates.Conclusions:Significant thymic involution occurs after I-131 therapy in patients with Graves disease. Serum T3, but not TRAb, may be related to thymic hyperplasia and involution following I-131 therapy.

Characteristics of distribution and quantity of dendritic cells subtypes in hyperplastic thymus in patients with myasthenia gravis

Objective: To investigate the characteristics of the distribution and amount of different subtypes of dendritic cell (DC) in myasthenia gravis(MG). Methods: We collected the thymic specimens from 32 patients who received thymoctomy because of cardiac surgery from January 2016 to December 2016 and selected 14 of them as normal control. Meantime, 61 MG patients who combined with thymic hyperplasia and received extended thymectomy were collected and selected 8 of them as experiment group.Immunohistochemical methods were used to label the two subtype DCs: plasmacytoid dendritic cell (pDC) and classical/conventional dendritic cell (cDC), to observe the distribution of these two DC subtypes in thymus and also quantify them in different thymus structures by image analysis software.Comparing with normal thymus of the same age, we intended to demonstrate the characteristics of distribution and density of DC subtypes in patients who had MG and hyperplastic thymus. Results: (1) We labeled pDC and cDC by staining with CD123 and CD11c.The two DC subtypes distributed in both cortex and medulla, and the majority gathered in medulla, the density of pDC in thymus cortex was (34±6)/mm(2)(n=14), the density of pDC in thymus medulla was (247±35)/mm(2)(n=14), the density of cDC in thymus cortex was (21±4)/mm(2)(n=14), the density of cDC in thymus medulla was (123±16)/mm(2) (n=14). (2) The density of pDC in thymus cortex and medulla of patients with MG was lower when compared with the normal group (the density of pDC in thymus cortex, [(39±10)/mm(2) vs (29±5)/mm(2)], the density of pDC in thymus medulla, [(279±48)/mm(2) vs (236±49)/mm(2)], but with no significant difference.There was no significant difference between the density of cDC in thymus cortex of patients with MG patients and normal people, however, the amount of cDC increases in medulla and the difference was statistically significant (P<0.05). (3) The density of cDC in thymus medulla (except for germinal center) was higher than normal people (110±18) /mm(2) vs (187±29/mm(2)), though the difference was not statistically significant (P=0.059 9). The density of cDC in the ectopic germinal center (GC) of MG patients increased obviously compared with that in thymus medulla [(203±44) /mm(2) vs (439±69)/mm(2)] and the difference was statistically significant (P<0.05). Conclusions: The density of cDC increases significantly in thymus medulla of MG patients, especially gathering around or in the ectopic GC. It indicates that cDC may play an important role in the formation of ectopic GC in the hyperplasia thymus, thus involves in the disease process.

Pathological Findings in Myasthenia Gravis Patients with Thymic Hyperplasia and Thymoma.

Thymectomy is routinely carried out in patients with myasthenia gravis (MG) and thymomas. However, there is still a dispute as to whether MG patients with thymic hyperplasia should undergo thymectomy. We aimed to investigate the pathological findings in the thymus in patients with co-existing MG and thymic hyperplasia or thymomas treated with thymectomy, as well as effects of immunosuppression. Thirty-three patients with MG were selected and grouped accordingly: patients with no thymic abnormalities, patients with thymic hyperplasia, and patients with thymomas. All patients were treated with methylprednisolone alongside immunosuppression. A separate cohort of 24 MG patients with thymic hyperplasia or thymomas and treated with thymectomy were selected. As controls, 5 patients with thymomas or thymic carcinoma without MG were selected. Expression of CD5, extracellular regulated protein kinases1/2 mitogen activated protein kinase (ERK1/2MAPKs) and CD95 ligand (FasL) in the thymus was examined. Methylprednisolone and immunosuppressive therapy are highly effective in MG patients with normal thymus tissue and MG patients with thymic hyperplasia compared to MG patients with thymomas alone. CD5 expression was highest in MG patients with thymic hyperplasia, correlating with expression of ERK1/2MAPKs. FasL expression was similar across all groups. Thymomas may be distinguished from thymic hyperplasia by expression of CD5 and ERK1/2MAPKs. Thymectomy is the preferred treatment for MG patients with thymomas but may not be necessary in MG patients with thymic hyperplasia who are treated with immunosuppressive therapy.

AMP-Deaminase from Thymus of Patients with Myasthenia Gravis

Myasthenia gravis (MG) is characterized clinically by skeletal muscle fatigue following the excessive exercise. Interestingly most of MG patients manifest parallely also some abnormalities of the thymus.AMP-deaminase (AMPD) from human thymus was not a subject of studies up to now. In this paper, mRNA expression and some physico-chemical and immunological properties of AMPD purified from the thymus of MG patients were described. Experiments performed identified the liver isozyme (AMPD2) as the main isoform of AMPD expressed in this organ. The activity of AMPD found in this organ was higher than in other human non-(skeletal) muscle tissues indicating on role the enzyme may play in supplying of guanylates required for the intensive multiplication of thymocytes.

Expression of barrier to autointegration factor-1 in thymus of patients with myasthenia gravis

Objective To observe the expression of barrier to autointegration factor-1 (BANF-1) in thymus tissue of myasthenia gravis (MG) patients,and discuss the relationship between BANF-1 and abnormal thymus of MG.Methods The total RNA was extracted by using Trizol from the thymus tissues of MG patients (30 cases of hyperplasia,22 cases of atrophy,and 20 cases of thymoma) and normal thymus (24 cases).The BANF-1 mRNA expression was detected by real-time fluorescent quantitative polymerase chain reaction (FQ-PCR).The expression of BANF-1 protein was detected by immunohistochemical staining.Results There was significant difference in the BANF-1 expression among four kinds of thymic tissues (F =3.627,P ＜0.05).As compared with normal controls (17.77 ± 13.01),hyperplasia patients (29.58 ±22.81) and thymoma patients (15.99 ± 16.33),the expression of BANF-1 gene in thymus atrophy patients (54.79 ± 35.13) was increased (P ＜ 0.01).Immunohistochemistry revealed the expression of BANF-1 in thymic tissues of hyperplasia,atrophy,and thymoma.Conclusion Differences in the expression level of BANF-1 may be related to the pathogenic mechanisms for abnormal thymus of MG patients,especially associated with MG thymus atrophy. Key words: Barrier to autointegration factor-1 ; Thymus ; Myasthenia gravis

Survivin as a potential mediator to support autoreactive cell survival in myasthenia gravis: a human and animal model study.

The mechanisms that underlie the development and maintenance of autoimmunity in myasthenia gravis are poorly understood. In this investigation, we evaluate the role of survivin, a member of the inhibitor of apoptosis protein family, in humans and in two animal models. We identified survivin expression in cells with B lymphocyte and plasma cells markers, and in the thymuses of patients with myasthenia gravis. A portion of survivin-expressing cells specifically bound a peptide derived from the alpha subunit of acetylcholine receptor indicating that they recognize the peptide. Thymuses of patients with myasthenia gravis had large numbers of survivin-positive cells with fewer cells in the thymuses of corticosteroid-treated patients. Application of a survivin vaccination strategy in mouse and rat models of myasthenia gravis demonstrated improved motor assessment, a reduction in acetylcholine receptor specific autoantibodies, and a retention of acetylcholine receptor at the neuromuscular junction, associated with marked reduction of survivin-expressing circulating CD20+ cells. These data strongly suggest that survivin expression in cells with lymphocyte and plasma cell markers occurs in patients with myasthenia gravis and in two animal models of myasthenia gravis. Survivin expression may be part of a mechanism that inhibits the apoptosis of autoreactive B cells in myasthenia gravis and other autoimmune disorders.

Sex Steroid Blockade Enhances Thymopoiesis By Modulating Notch Signaling

Thymopoiesis is a complex process dependent on precise signals from the supporting thymic stromal microenvironment that orchestrates the progression of precursor T cells through well-defined maturation stages. It is well documented that the decline in thymic size and function with age is in part correlated with an increase in sex steroids. This age-related decline in function can be detrimental to the recovery of the thymus in patients receiving radio or chemo-therapy with hematopoietic stem cell transplantation (HSCT). Delayed immune reconstitution, especially in the T cell lineage, is associated with an increased risk of opportunistic infections and malignant relapses. Therefore strategies to enhance thymic reconstitution has the potential to decrease the period of T cell lymphopenia and increase overall clinical outcome.In the process of evaluating the effects of sex steroids in the decline of the thymic function, we found a decrease in the expression of the key thymopoietic factors IL-7, CCL25 and Delta-like 4 (DLL4) by thymic stromal cells after testosterone treatment (Figure 1A). We then addressed if these transcriptional changes were the result of a direct regulation by the androgen receptor (AR). Using a computational approach, and subsequently confirmed by ChIP studies, we found that AR directly bound and negatively regulated the promoter of DLL4, a critical gene involved in T cell commitment and differentiation. We and others have previously shown that sex steroid ablation (SSA) can regenerate young and aged immune system by promoting bone marrow and thymic lymphopoiesis and promoting recovery from autologous and allogeneic HSCT. However the mechanisms underlying the sex steroid-mediate thymic involution and its regeneration after SSA are poorly understood. Moreover, one of the main drawbacks to standard clinical methods of sex steroid ablation using luteinizing hormone releasing hormone (LHRH) agonists (LHRH-Ag) is the initial surge in sex steroids they cause. To address this, we employed a novel class of LHRH-antagonists (LHRH-Ant) that rapidly block the secretion of sex steroids without causing their initial surge that can be even more detrimental to thymopoiesis. Mice treated with LHRH-Ant showed a significantly faster increase in thymic cellularity compared with LHRH-Ag treated mice (Figure 1B). Given the negative regulation of DLL4 by the AR, we hypothesized that DLL4 expression would conversely increase after SSA in vivo. Indeed, we found a significant increase in DLL4 expression after SSA and also an increase in genes downstream of DLL4, such as Ptcra, Hes1 and Cd25 (Figure 1C). We next evaluated if treatment with the LHRH-Ant would provide a faster immune recovery after injury to the immune system. We found that mice treated with LHRH-Ant showed a faster thymic regeneration after total body irradiation (TBI) compared to the control irradiated mice (Figure 1D) and enhanced viral clearance (Figure 1E). Finally, we also found that LHRH-Ant enhanced thymic and peripheral reconstitution up to 3 months after allo-HSCT (Figure 1F). [Display omitted] In conclusion, we found that down-regulation of DLL4 may represent one of the mechanisms underlying the effects of sex steroids on thymic function. We demonstrate that SSA with a novel LHRH-Ant increases DLL4 expression and enhances thymic and peripheral T cell recovery and function after immune injury. These findings suggest that the employment of a LHRH-Ant, which is already in clinical use for prostate cancer patients, represents a novel therapeutic strategy to enhance immune recovery and function in immunocompromised patients. Disclosures:No relevant conflicts of interest to declare.

The role of B cell–activating factor in autoimmune myasthenia gravis

B cell-activating factor (BAFF) is important in the development and maturation of B cells and their progeny-plasma blasts and plasma cells. There is increasing evidence that BAFF is involved in the pathogenesis of several autoimmune diseases including myasthenia gravis. Increased expression of BAFF and receptors for BAFF have been demonstrated in thymus of patients with myasthenia gravis, and an increase in serum levels of BAFF have been reported in patients with myasthenia gravis. While the exact role of BAFF in the pathogenesis of myasthenia gravis is not clear, BAFF and its receptors may provide potential targets for therapy in patients with myasthenia gravis.

Association of Type-O Blood with Neuroendocrine Tumors in Multiple Endocrine Neoplasia Type 1

The ABO blood type system describes the expression of human blood group antigens found on both erythrocytes and normal tissue throughout the body. We recently reported an association between O blood type and the manifestation of pancreatic neuroendocrine tumors in a cohort of patients with Von Hippel-Lindau syndrome. The aim of the study was to determine whether there is an association of ABO blood type with the development of neuroendocrine tumors in patients with multiple endocrine neoplasia, type 1 (MEN-1). A retrospective analysis of 105 patients with MEN-1 was performed. Demographic, clinical, and biochemical data were analyzed by ABO blood type. Fisher's exact test was used to determine association between ABO blood type and manifestation of neuroendocrine tumor. Demographic and clinical characteristics were similar amongst blood type cohorts. We found an association between O blood type and the manifestation of a primary neuroendocrine tumor of the gastrointestinal tract, lung, pancreas, and thymus in patients with MEN-1 (P = 0.01). Sixteen of 17 (94%) metastatic tumors had type-O blood, compared to 32 of 43 (74%) with a benign tumor who had non-O blood type. Our findings suggest an association between O blood type and the manifestation of a primary neuroendocrine tumor in patients with MEN-1. Prospective clinical studies are warranted to see whether patient blood type status may be a useful addition to current screening and surveillance practices.

Detection of poliovirus-infected macrophages in thymus of patients with myasthenia gravis

Genetic and environmental factors are thought to contribute to the etiology of the autoimmune disease myasthenia gravis (MG). Viral involvement has long been suspected, but direct evidence of involvement has not been found. We recently reported that Toll-like receptor 4 (TLR4)-a key activator of innate immunity-was overexpressed in the thymus of some patients with MG, suggesting that thymic infection by pathogens might be involved in MG pathogenesis. We searched for evidence of intrathymic infection in patients with MG. Twenty-seven MG thymuses (6 involuted, 7 hyperplastic, 5 thymitis, and 9 thymoma) previously tested for TLR4 expression, 18 nonpathologic control thymuses, and 10 pathologic control thymuses from patients without MG (8 thymoma and 2 hyperplastic) were analyzed for cytomegalovirus, varicella-zoster virus, herpes simplex virus types 1 and 2, eubacteria, respiratory syncytial virus, and enteroviruses using PCR techniques. Immunohistochemistry and double immunofluorescence were used to detect enterovirus capsid protein VP1 in thymic specimens and analyze TLR4 expression in VP1-positive cells. Poliovirus was detected in 4 MG thymuses (14.8%; 2 thymitis and 2 thymoma). No virus was detected in any control thymus. A linear correlation between plus and minus strand poliovirus RNA levels was observed in all 4 thymuses, suggesting persistent thymic infection. VP1 protein was detected in the cytoplasm of CD68-positive macrophages scattered through thymic medulla in all PV-positive thymuses. VP1 and TLR4 colocalized in infected cells. Poliovirus-infected macrophages are present in thymus of some patients with myasthenia gravis, suggesting a viral contribution to the intrathymic alterations leading to the disease.

Undiminished regulatory T cells in the thymus of patients with myasthenia gravis

The thymus has been implicated as a possible site of origin that triggers autoimmunity in myasthenia gravis (MG). Although several groups have suggested that the decrease in the number of regulatory T (Treg) cells contributes to the onset of MG, the exact role of Treg cells in MG remains unclear. To address this point, we examined the number and distribution of Treg cells in a large number of patients with MG. Immunohistofluorescence analysis of Foxp3 along with CD4 and CD8 was performed in thymic sections of MG (+) (n = 24) and MG (-) patients (n = 27). Circulating CD4(+)CD25(+) cells in the peripheral blood of patients with MG (n = 15) and age-matched healthy subjects (n = 15) were also analyzed. Foxp3(+)CD4(+)CD8(-) cells were predominantly found in the thymic medulla and their number declined with age. There was no significant difference in the number or the distribution of Foxp3(+)CD4(+)CD8(-) cells in the thymus between MG (+) and MG (-) patients. The number of circulating CD4(+)CD25(+) cells in the peripheral blood of patients with MG was not significantly altered compared to that in healthy subjects. The cellularity of Treg cells in the thymus and circulation is not diminished in patients with myasthenia gravis.

Long-term follow up of thymus in patients with myasthenia gravis

We examined transversely the thymus of 33 myasthenia gravis (MG) patients followed up for more than 5 years and found three thymomas. One was found 21 years after thymoma resection (Masaoka I, WHO Type B2 thymoma) and extended thymectomy. The other two were non-thymomatous at onset, and they were not treated with extended thymectomy. Therapeutic guidelines should mention the importance of follow-up in MG thymus.

Defect of regulatory T cells in patients with Omenn syndrome

Omenn syndrome (OS) is an autosomal-recessive disorder characterized by severe immunodeficiency and T-cell-mediated autoimmunity. The disease is caused by hypomorphic mutations in recombination-activating genes that hamper the process of Variable (V) Diversity (D) Joining (J) recombination, leading to the generation of autoreactive T cells. We have previously shown that in OS the expression of autoimmune regulator, a key factor governing central tolerance, is markedly reduced. Here, we have addressed the role of peripheral tolerance in the disease pathogenesis. We have analyzed forkhead box protein P3 (FOXP3) expression in peripheral blood T cells of 4 patients with OS and in lymphoid organs of 8 patients with OS and have tested the suppressive activity of sorted CD4(+) CD25(high) peripheral blood T cells in 2 of these patients. We have observed that CD4(+)CD25(high)T cells isolated ex vivo from patients with OS failed to suppress proliferation of autologous or allogenic CD4(+) responder T cells. Moreover, despite individual variability in the fraction of circulating FOXP3(+) CD4 cells in patients with OS, the immunohistochemical analysis of FOXP3 expression in lymph nodes and thymus of patients with OS demonstrated a severe reduction of this cell subset compared with control tissues. Overall, these results suggest a defect of regulatory T cells in OS leading to a breakdown of peripheral tolerance, which may actively concur to the development of autoimmune manifestations in the disease.

Thymic Hyperplasia and Graves Disease: Management of Anterior Mediastinal Masses in Patients with Graves Disease

To describe a case of an anterior mediastinal mass (AMM) in a patient with Graves disease. We report the clinical presentation, diagnosis, management, and outcome of a 34-year-old man with dyspnea on exertion. Initial evaluation of the patient's complaints revealed a large AMM on chest radiography and then chest computed tomography. After occurrence of additional symptoms, the patient was diagnosed as having Graves disease and treated with antithyroid medications. Despite an appropriate biochemical response, he continued to experience severe dyspnea on exertion. A repeated computed tomographic scan 8 weeks after initiation of therapy showed no appreciable decrease in size of the AMM. He elected to undergo thymectomy. An intraoperative phrenic nerve injury resulted in a paralyzed left hemidiaphragm, leaving the patient with considerable difficulties in his career and profoundly decreased exercise tolerance. The differential diagnosis of an AMM includes several malignant lesions with a risk often warranting early surgical excision. In light of the association of benign thymic hyperplasia with Graves disease, thymectomy may be delayed in expectation of thymic regression with medical therapy. The timing of regression is variable, and very few reports exist in the literature. In our current case, the patient opted for thymectomy relatively early and had an unfortunate complication. The lack of clinical evidence regarding management of an enlarged thymus in patients with Graves disease, however, makes management decisions more difficult.

Incidence of Parathyroid Glands Located in Thymus in Patients with Renal Hyperparathyroidism

Parathyroid glands are frequently located in thymus, and it is essential to resect thymic tissue from the neck incision, especially in surgery for renal hyperparathyroidism (HPT). In this study, we evaluated the incidence, location, and type of intrathymic parathyroid glands in 902 patients who underwent initial parathyroidectomy (PTx) for advanced renal HPT in our department. Removal of the thymic tongues on both sides was routinely performed from the neck incision, and the thymic tissue was carefully examined both macroscopically and microscopically. Of the 902 patients in the study, 269 had only inferior parathyroid glands in the thymus, in 62 patients only supernumerary glands were found in the thymic tongue, and in 78 patients both inferior and supernumerary glands were present in thymic tissue. Therefore the incidence of patients with intrathymic glands was 45.3% (269 + 62 + 78 = 409/902). In 129 (92.1%) of 140 patients with supernumerary glands in the thymic tongue, these glands were detected only on histopathological examination, and about half of them were classified as the parathyromatosis type. In the human, parathyroid glands might be located in the thymus in about 50%. If the inferior gland/glands cannot be found around the inferior pole of thyroid lobe, it is very important to search for glands in the thymic tongue. Moreover, to avoid missing supernumerary glands, removal of the thymic tongue on both sides is essential in surgery for renal HPT.

Microscopic-Sized “Microthymoma” in Patients With Myasthenia Gravis

Background:In 2005, Cheuk et al reported two patients with microscopic-sized thymomas and proposed the termmicrothymomato distinguish it from the nodular hyperplasia of thymic epithelium, so-calledmicroscopic thymoma. Here, we present microthymomas that were found in 196 patients with myasthenia gravis (MG) who had undergone thymectomy.Materials and methods:Thymic tissues in 196 patients with MG who underwent thymectomy or thymothymomectomy were examined. Of these patients, 73 patients had thymoma indicated by CT before surgery, and the other 123 patients had no mediastinal tumors. From the resected thymic tissues, an average of 14 hematoxylin-eosin–stained sections (range, 4 to 55 sections) were prepared for microscopic examination. The histologic type of the thymoma was classified according to the World Health Organization (WHO) classification.Results:From the 196 patients, we found three microthymomas in 3 patients (1.5%). While these three tumors could not be seen grossly in pathology section, they were found microscopically (range, 2 to 4 mm). The histologic subtype according to the WHO classification system was B1 in one patient and B2 in two patients.Conclusion:Microthymoma was found in 3 of 196 patients (1.5%) with MG. Microthymoma might exist in thymus of patients with MG, even in patients who have no thymoma indicated by CT.