Massive true thymic hyperplasia

A case of massive true thymic hyperplasia in a child of eleven months is described. This rare disorder must be included in the differential diagnosis of a mediastinal mass in children. Diagnosis and management are discussed and the relevant literature is reviewed.

Early and late results after thymectomy in myasthenia gravis: a retrospective study [correction of analysis]

BACKGROUND

This study aims to evaluate the early and late outcome of patients treated by surgery for myasthenia gravis and the diagnostic value of the Besinger Score, which is based on a correlation of severity of symptoms with specific antibodies to acetylcholine receptors, in the follow-up investigation after surgical therapy.

METHODS

Between June 1984 and April 1992 thoracotomy was performed in 51 myasthenia gravis cases at our department. The retrospective analysis considered patients with (n = 13) or without thymoma (n = 38). The Besinger score was used to describe the severity of disease preoperatively and up to 5 years postoperatively.

RESULTS

The Besinger score fell continually post surgery. Changes in relative serum concentrations of antibodies were similar to the Besinger score. Five years after thymectomy complete remission was diagnosed in 40% of the patients. The required dosage of pyridostigmine had fallen by two thirds after 5 years. Patients with follicular hyperplasia had significantly higher remission rates than those with thymoma.

CONCLUSIONS

Surgery for myasthenia gravis is successful. The Besinger score well quantifies the severity of the disease.

[Hypophyseal-adreno-gonadal system function in myasthenia patients with tumorous and nontumorous pathology of the thymus]

Overall twenty-five patients (all women) who ranged from 16 to 56 years old were examined. They were divided into two groups: group I was formed of subjects with hyperplasia of the thymus gland, group II--thymoma. Blood serum levels of prolactin, progesterone, estriol, estradiol, testosterone hydrocortisone. All patients showed a significant increase in average blood plasma levels of estrogens, testosterone and prolactin. Average levels of progesterone and hydrocortisone in patients with thymus hypertrophy were lower than in controls, while in thymoma patients these were much higher. The data submitted are indicative of substantial differences in the endocrine status of myasthenia patients depending on tumor or nontumor lesion of the thymus gland, which fact may suggest different pathogenetic mechanisms of development of the condition.

Thymectomy in black children with juvenile myasthenia gravis

Fifteen black children with juvenile myasthenia gravis presented to our institution over a 10-year period at ages ranging from 18 months to 7 years, 4 males and 11 females. Twelve presented with progressive, generalised weakness and 3 had bulbar manifestations. Ocular signs were absent in 2 patients. All 15 patients were placed on pyridostigmine bromide (Mestinon) and 1 also required steroids and plasmapheresis. Medical therapy only was instituted in 5 patients, of whom 2 came to surgery, 2 died, and 1 was lost to follow-up. Thymectomy was performed in 12 children (including the 2 with failed medical therapy) via a median sternotomy with no mortality or morbidity related to the operation. The timing of surgery was less than 3 months in 75% of the children. Thymic hyperplasia was noted in 10 glands and 2 were reported as normal. Of the children in the operative group, 83% are on minimal medication or in total remission. Better results were noted in young patients with early thymectomy and diseased glands.

Hyperplasia of thymic gland

Hyperplasia of the thymus is the most common anterior mediastinal mass in infants. It is however exceedingly difficult to evaluate by the weight of the gland as it continues to grow after birth until puberty and thereafter undergoes progressive atrophy. It normally maintains most of the radiographic characteristics of the normal thymus. Massive thymic hyperplasia, a rare variant of true thymic hyperplasia is extremely rare during the first two decades of life and clinically can cause mediastinal compression or acute and recurrent pulmonary infection. Two such cases are reported and the clinico-pathology is briefly described and discussed.

Detection and morphology of thymic remnants after video-assisted thoracoscopic extended thymectomy (VATET) in patients with myasthenia gravis

Thymectomy is often an extremely useful therapeutic procedure in myasthenia gravis (MG) and is usually indicated for adult patients with generalized disease. Because remnants of thymus may remain in extrathymic fat, an extended thymectomy is recommended. A new surgical approach without sternotomy: video-assisted thoracoscopic extended thymectomy (VATET) was performed in 30 MG patients. The weight of removed thymus ranged from 10.8 to 113 grams. The weight of fatty tissue removed from pretracheal, anterior mediastinal and costophrenic areas ranged from 6.3 to 74.8 grams. Histological examination revealed thymic remnants in 14.8% of pretracheal fat samples and in 33.3% of samples from anterior mediastinal plus costophrenic areas. These findings indicate that VATET is a radical procedure and may be the first choice surgery for young female MG patients, since aesthetic sequelae are reduced compared to procedures involving sternotomy.

[Imaging of the thymus gland in myasthenia gravis (computerized tomography and magnetic resonance)]

Since thymectomy is nearly always indicated as a possible treatment of myasthenia gravis, we examined with Magnetic Resonance (MRI) and Computed Tomography (CT) 22 patients (21-62 years old) to identify the best methodological approach. MR images were obtained with a 1.5 T superconducting unit with slice thickness ranging from 6 to 8 mm and an interslice gap of 0.6 and 0.8 mm. Spin-echo images were acquired with repetition time (TR) < 700 ms and echo time (TE) of 20 ms and T2-weighted images with TR > 1800 ms and TE of 80 ms. The sections were obtained, with cardiac gating, on transverse and sagittal planes. CT was performed with contiguous 5-mm slice thickness, after intravenous bolus injection of contrast medium. All the patients underwent surgery of anterior mediastinum and histologic diagnosis was made. Both CT and MRI correctly identified the patterns of normal thymus or hyperplasia not associated with gland enlargement, the only two cases of hyperplasia with thymic enlargement and clearly demonstrated thymomas. MRI appears to be more accurate in the evaluation of the relationship between thymus and contiguous structures. If pericardial infiltration is suspected, sagittal MR scans yield accurate information on tumor spread. We recommend MRI of anterior mediastinum to rule out the presence of a thymoma and the possible involvement of contiguous structures.

[Thymic lymphoid hyperplasia of myasthenia gravis patients: correlation with clinical features and efficacy of thymectomy]

Thirty nine thymus tissues from myasthenia gravis patients without thymoma who underwent extended thymectomy were evaluated on thymic lymphoid hyperplasia with special emphasis on clinical features and the efficacy of thymectomy. Of 39 patients, 31 were women, but 3 of 7 patients without thymic lymphoid hyperplasia were men. The hyperplastic index of the thymus correlated largely with serum anti-Ach-R antibody titers before surgery. Age, myasthenic type and preoperative duration of the symptoms were almost unrelated to the hyperplastic change in the thymus. The effect of thymectomy was more remarkable in the patients with the hyperplastic thymus than that in them without it, who obtained still no remission after surgery, although the remission rate of them with it reached to 25%. Of 7 patients without the hyperplastic thymus, 4 had no detectable antibody to acetylcholine receptor, whereas in 32 patients with it only 2 were seronegative. This negative immunological factor might make adverse response to thymectomy. Although unfavorable response to thymectomy were observed in the patients without the hyperplastic thymus, most of them were significantly improved through a supplementary treatment with steroid after surgery. Thymectomy was a favorable treatment for myasthenia gravis patients with thymic lymphoid hyperplasia, whereas in them without it the result of thymectomy was unsatisfactory.

Maximal thymectomy for myasthenia gravis

Maximal thymectomy was carried out in 48 patients with myasthenia gravis (MG). There were 18 males and 30 females. Thymic hyperplasia was found in 38, and atrophic thymus in 8, patients. Two patients had thymoma. In the non-thymomatous myasthenia gravis complete remission was achieved in 16 patients (34.8%) and pharmacological remission in 20 patients (43.5%) thus giving a total remission in 36 (78.3%) patients. Six patients (13%) improved. There was no improvement in four patients. Thus, the overall benefit from thymectomy was 91.4% in this series. We found that sex, age at onset of disease and steroid therapy influenced the outcome of thymectomy. On the other hand, duration of disease, anti-acetylcholine receptor (AntiAchR) antibodies and thymic histology did not have any bearing on the complete remission rate.

[Paraneoplastic Cushing's syndrome. Pseudotumors of the thymus occurring after correction of hypercorticism. 3 cases]

Ectopic ACTH-secreting tumours responsible for paraneoplastic Cushing's syndrome are invisible at radiography in about 50 percent of the cases. In this situation, the current attitude is to correct the hypercorticism and then embark on a regular morphological monitoring in search of the initial tumour with the purpose of removing it. We report the cases of 3 patients who had a paraneoplastic Cushing's syndrome of unknown origin in 1 case and consecutive, in 2 cases, to a bronchial carcinoid tumour initially occult and discovered 30 and 42 months respectively after the onset of the disease. Six to 10 months after hypercorticism was cured with ketoconazole and bilateral adrenalectomy, a thymic mass 2 to 5 cm in length was detected by computerized tomography or magnetic resonance imaging in all 3 patients. At resection of the thymus, performed in 2 cases, a benign hyperplasia of this organ with negative immunohistostaining for ACTH was discovered. This abnormality, seldom reported, seems to result from the abrupt cessation of hypercorticism. It must be known to avoid an unnecessary thymectomy during supervision of patients with paraneoplastic Cushing's syndrome related to a radiologically occult tumour.

Rebound thymic hyperplasia following high dose chemotherapy and allogeneic BMT

We describe a child with acute lymphoblastic leukemia who showed mediastinal widening 8 months after allogeneic BMT. Total thymectomy was carried out by the transcervical approach. Histologic examination showed only thymic hyperplasia. The immunohistologic investigation revealed a normal distribution of thymic cell elements, without evidence of clonal proliferation of lymphocytic subpopulations. This case supports the hypothesis that thymic hyperplasia following chemotherapy may be merely a rebound phenomenon. The patient had an uneventful postoperative recovery and remains in remission more than 1 year after BMT.

Thymectomy in myasthenia gravis. The Jamaican experience

Forty-five patients with myasthenia gravis (MG) were subjected to thymectomy by the median sternotomy technique and were followed up for 4,380 patient months. No operative deaths occurred and 93.3% of the patients benefited from surgery with 28.8% achieving remission. Forty patients (88.5%) showed improvement within one month, and 73% of those who achieved remission did so in the first 2 years. Outcome was not affected by thymic pathology except in one patient who had a thymoma removed. These results confirm the value of thymectomy in the management of MG patients with generalised disease and the efficacy of the simple median sternotomy procedure.

Thymic enlargement in children

The presence of an anterior mediastinal mass in an infant or child is a diagnostic and therapeutic challenge. Few papers in the literature specifically address subtypes of thymic tumors in the pediatric population and their treatment. Our purpose was to determine which children are at significant risk of having a malignant thymic tumor. Four children were younger than 18 months old. Of these, two (50%) had respiratory distress from tracheal compression although all four had benign tumors. Of the 14 older children, only two were symptomatic, both of these from myasthenia gravis rather than the size of the mass compressing surrounding structures. Four of the 14 masses (29%) were malignant although none of the four were symptomatic. Children with benign tumors lived significantly longer than those with malignant tumors. The significant incidence of malignancy in thymic tumors when the patient is 18 months or older necessitates surgical exploration with complete removal of the mass. Children younger than 18 months require close follow-up and a trial of corticosteroids. Surgery is necessary if the mass enlarges or becomes symptomatic.

[Indications for thymectomy]

An absolute indication for thymectomy exists in all cases with tumors of the thymus gland, however, preoperative differentiation between benign and malignant lesions is not always possible even with modern imaging methods. In extensive tumors of questionable operability preoperative transthoracic needle biopsy (guided by CAT-scan) is recommended. After establishing the histological diagnosis, preoperative radio- and/or chemotherapy can be considered. Certain immunological diseases are a relative indication for thymectomy. Its value is proven in myasthenia gravis, questionable however in ulcerative colitis and erythroblastopenia. Systemic lupus erythematosus is a contraindication.

Thymic rebound in an adult following chemotherapy for testicular cancer

Thymic hyperplasia is reported in a 27 year old man following combination chemotherapy for metastatic testicular cancer. The occurrence of this phenomenon is reviewed and the implications for management discussed.

Thymic hyperplasia masquerading as recurrent Hodgkin's disease: case report and review of the literature

While the appearance of a mediastinal mass in a patient in remission from Hodgkin's disease frequently indicates recurrence, a number of benign processes may present in a similar manner. Tissue confirmation of relapse should be obtained prior to initiating further chemotherapy to avoid the morbidity of unnecessary treatment. We present a case of thymic hyperplasia that developed in a patient previously treated for Hodgkin's disease. Thymic hyperplasia is a poorly understood, apparently benign process that may be confused with recurrent lymphoma. Total excision of such a mass is recommended to rule out coexistent malignancy.