Abstract
Simple SummaryThe thymus is the last organ in the human body to have its mechanisms fully understood. Its intrinsic complex morpho-functional structure reflects the complexity and variety of the pathological lesions of the gland. These include some variants of neoplastic and nonneoplastic processes, which are considered the rarest of the rare ones. The aim of this work is to describe the rarest lesions of the thymus in a large case series in order to update the epidemiology, to improve diagnostic awareness, and finally to promote a collaborative network between referral centers.The thymus is a specialized primary lymphoid organ located in the midline pre-vascular mediastinum. The organ is the site of various pathological processes, neoplastic and not, whose rarity has not allowed in-depth studies on clinical or histological features of rarest and unusual variants. Herein, we report a 10-year Padova experience in the surgical pathology of the thymus, focusing on the pathological description of nonneoplastic lesions and rare epithelial and mesenchymal tumors recorded in our database, which comprises over 600 thymectomies. The extrapolated rare cases have been categorized into four groups that included 15 cysts, 18 carcinomas, 5 neuroendocrine tumors, and 2 soft tissue tumors. The cases are described from a clinical and pathological point of view and discussed in dedicated sections with a review of the most important literature. In this case, review series, we aim to update the epidemiology of these rare entities, improve diagnostic awareness, and finally, promote a collaborative network between referral centers.
Highlights
The thymus is a specialized primary lymphoid organ located in the midline anterosuperior mediastinum, essential for the maturation of T lymphocytes, which orchestrate adaptive immune responses [1]
We report a 10-year Padova experience in the surgical pathology of the thymus, focusing on the pathological description of rare epithelial and mesenchymal tumors and nonneoplastic lesions recorded in our database, which comprises over 600 thymectomies
Thymic cysts were first described in 1850 [11] and represent a very rare lesion accounting for about 1% of all mediastinal cysts [12]
Summary
The thymus is a specialized primary lymphoid organ located in the midline anterosuperior mediastinum, essential for the maturation of T lymphocytes, which orchestrate adaptive immune responses [1]. The complex morpho-functional structure of the organ reflects the complexity and variety of the pathological lesions of the thymus. The surgical pathology of the thymus encompasses a heterogeneous group of rare entities [2] which almost exclusively arise in the prevascular mediastinum with the exception of ectopic thymic tissue lesions. Since the first description of the association between myasthenia gravis (MG) and thymomas in the early 1900s [6], the study of thymic pathology has generated great scientific interest by several groups both in understanding the development of these rare neoplasms and especially in improving lesion classification. Few topics in pathology have been debated as much as the classification of thymic epithelial tumors, on which agreement has only been reached in recent years [7]. The field is further complicated by the presence of numerous and rare histological variants of epithelial, mesenchymal, lymphohematopoietic, and germinal origin with challenging pathological diagnoses, especially in limited small biopsy material
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