Hyperplastic Thymic Tissue Research Articles

Lipofibroadenoma arising in hyperplastic thymic tissue: Possible perivascular origin of lipofibroadenoma

Lipofibroadenoma arising in hyperplastic thymic tissue: Possible perivascular origin of lipofibroadenoma

A rare association between true thymic hyperplasia and thyroid follicular tumor: a case report

BackgroundTrue thymic hyperplasia is a rare condition characterized by enlargement of the thymus while its normal structure is retained. True thymic hyperplasia is known to accompany Graves’ disease, but no association between true thymic hyperplasia and thyroid follicular tumor has been reported so far. We report a case of true thymic hyperplasia in a patient with a thyroid follicular tumor.Case presentationA 52-year-old Japanese man was referred to our hospital for evaluation of a thyroid mass and a mediastinal mass. His serum thyroglobulin level was high, and hemithyroidectomy was performed to remove the thyroid mass. The resected mass was diagnosed as a follicular tumor of uncertain malignant potential. After resection of the thyroid lesion, the patient’s serum thyroglobulin levels were markedly decreased. Seven months later, the patient underwent resection of the mediastinal mass. On pathological examination, the mass was found to consist of lobules, which formed a corticomedullary structure with Hassall’s bodies, indicating a normal thymic mass with hyperplastic thymic tissue, less organized cellular cords, and intermingled adipose tissue. Immunostaining for cytokeratin 19 and cytokeratin 7 indicated that the lesion was consistent with thymic tissue. The lesion was diagnosed as true thymic hyperplasia, and the histological findings suggested that secondary atrophy had occurred. No evidence of recurrence was observed at 24 months after surgery.ConclusionsWe present a case of a combination of true thymic hyperplasia and thyroidal follicular tumors that, to our knowledge, has not been reported previously. High serum thyroglobulin levels might play a role in hyperplasia of the thymus. Although true thymic hyperplasia is a rare disorder, it should be included in the differential diagnosis of a mediastinal mass in patients with thyroid disease.

Malignant mast cell tumor of the thymus in an Royal College of Surgeons (RCS) rat

A 152-week-old male Royal College of Surgeons (RCS) rat kept as a non-treated animal in a long-term animal study presented with a soft mass in the anterior mediastinum, which adhered to the pleura of the lung. Histopathologically, the mass mainly consisted of round to short spindle-shaped tumor cells that had infiltrated through the hyperplastic thymic tissue. The tumor cells were arranged in loose to dense sheets. Nuclei were moderate in size and round to spindle-shaped, with small nucleoli. Almost all tumor cells exhibited abundant eosinophilic cytoplasm, including eosinophilic granules of a range of sizes. The granules of tumor cells exhibited metachromasia with toluidine blue stain and were positive for c-kit and mast cell protease II. These findings indicate that the tumor described here represents a rare case of spontaneous malignant mast cell tumor with thymic epithelial hyperplasia.

Intrathymic ectopic parathyroid adenoma caused primary hyperparathyroidism with vitamin D deficiency several years after bariatric surgery.

Up to 25% of patients with primary hyperparathyroidism have ectopic parathyroid adenoma. A 45-year-old formerly obese woman underwent extended thymectomy for a parathyroid adenoma located in hyperplastic thymic tissue, associated with primary hyperparathyroidism and severe vitamin D deficiency, but normal bone mineral density. At nine months follow-up, all laboratory test results were within normal limits and she presented no symptoms and no recurrence of disease. In this case, autonomous growth of a parathyroid adenoma was reasonably secondary to chronic calcium and vitamin D malabsorption, which often occurs after bariatric surgery for pathologic obesity.

Thymic Hyperplasia after Lung Transplantation Imitating Posttransplant Lymphoproliferative Disorder

Thymic hyperplasia is usually associated with the treatment of malignant tumours and is sometimes linked with endocrine diseases. For the first time, we report a case of thymic hyperplasia in a patient 2 years after bilateral lung transplantation. Contrast-enhanced chest CT scan was highly suspicious for a posttransplant lymphoma or thymoma. Therefore, the patient received total thymectomy. Excised specimens were sent to the Department of Pathology. Unexpectedly, the histological examination revealed hyperplastic thymic tissue without evidence for a posttransplant lymphoproliferative disorder or malignancy.

Thymolipoma, Report of a Case Suggesting an Origin From Thymic True Hyperplasia

The authors describe a rare case of thymolipoma in a 26-year-old, otherwise healthy woman presenting with general fatigue. Radiological examinations disclosed a large anterior mediastinal mass. Macroscopically, the resected tumor was approximately 5 × 10 cm², with nodular configuration, and microscopically, 3 components were identified: a normal thymic rim, hyperplastic thymic tissue, and a typical thymolipomatous component at the periphery of the hyperplastic area. The predominant component of the tumor was hyperplastic thymic tissue. The tumor was diagnosed as thymolipoma at the initial stage of development. This case suggests the histogenesis of thymolipoma-fatty regression or infiltration of fatty tissue into a previously hyperplastic thymus.

Thymic Neoplasia as Represented by Fine Needle Aspiration Biopsy of Anterior Mediastinal Masses

To evaluate the cytomorphology of thymoma and to discuss the potential diagnostic pitfalls and a practical approach, which sometimes uses ancillary studies, in distinguishing various lesions of anterior mediastinal masses. A review of 25 fine needle aspiration (FNA) specimens of anterior mediastinal masses of thymic origin from 24 patients. The FNA diagnoses were thymoma in 16 aspirates, thymic/poorly differentiated carcinoma in 2, necrotic fluid/debris in 2, small lymphocytic proliferation in 2, hyperplastic thymic tissue in 1, benign cyst in 1, and scant tissue in 1. In 22 cases that had histologic confirmation, the diagnoses of 19 (86%), including 14 thymomas, concurred with the FNA diagnoses. Sampling error was responsible for the discrepancy in the remaining three cases. The cytologic evaluation of thymoma revealed a characteristic dual population of predominantly small lymphocytes and occasional large, atypical lymphocytes intimately admixed with relatively bland epithelial cells. Differential diagnoses of thymoma in the mediastinal aspirates included a variety of entities, depending on which component predominated. FNA of anterior mediastinal thymic lesions generally yields adequate cellular tissue with distinct cytologic and immunophenotypic features that enable precise classification. Caution in interpretation should be taken when the FNA yields only necrotic fluid or scanty material or when the patient is younger than the typical age range for thymoma. When the FNA diagnosis is coupled with clinical and radiographic findings, a definitive diagnosis can be generally rendered without open biopsy.

Lymphocyte subpopulations in thymus and blood from patients with myasthenia gravis.

Cell suspensions were prepared from hyperplastic thymic tissue and lymphoepithelioma from patients with myasthenia gravis and from presumed normal thymic tissue obtained at cardiac surgery. The mononuclear cells were examined for surface markers. The mean percentages of both T lymphocytes and Fc receptor-carrying lymphocytes were similar in the three groups, whereas there was an increase in C receptor-carrying lymphocytes in the samples from myasthenic patients. Sections from the thymus gland were examined for T and B markers. In the hyperplastic thymus and in lymphoepithelioma, the T lymphocytes were distributed diffusely throughout the cortex and the medulla; in the normal thymus they were predominant in the cortex. The mean percentage of T and B lymphocytes in peripheral blood from patients with myasthenia gravis was normal. Thymectomy involved a transitory decrease in T lymphocytes with a corresponding increase in B lymphocytes.