Intrathyroidal epithelial thymoma/carcinoma showing thymus‐like differentiation; comparison with thymic lymphoepithelioma‐like carcinoma and a possibility of development from a multipotential stem cell

Abstract

The purpose of our article is to describe the immunohistochemical findings of intrathyroidal epithelial thymoma/carcinoma showing thymus-like differentiation (ITET/CASTLE) of the thyroid in detail, to clarify the difference between ITET/CASTLE and thymic lymphoepithelioma-like carcinoma (LELC), and to discuss the pathogenesis of ITET/CASTLE. We immunohistochemically examined five ITET/CASTLE and eight LELC cases. All of ITET/CASTLE cases were strongly positive for CD5, P63, high-molecular-weight cytokeratin and B-cell CLL/lymphoma-2. Carcinoembryonic antigen-positive carcinoma cells were found in four ITET/CASTLE cases. Neuroendocrine marker-positive carcinoma cells were scattered in all cases. Immunohistochemical findings in thymic LELC were essentially similar to those in ITET/CASTLE, but the sensitivity was different. There is a possibility that ITET/CASTLE and thymic LELC are not the quite same disease entity. We think that ITET/CASTLE is derived from ectopic thymus, but not related to solid cell nests.

Clinical outcome of intensity modulated radiotherapy for carcinoma showing thymus-like differentiation

“…However, CD5 seems to be the only potential marker [17, 19, 20]. The positive expression rates of CD5 in the literature ranged from 75% to 100% [6, 15, 18, 21, 22]. In the present study, we found that 85.7% of the cases expressed CD5 totally or partially.…”

Intrathyroidal thymic carcinoma exhibiting neuroendocrine differentiation: Case report with cytomorphology, immunocytochemistry, and review of the literature focusing on cytology

“…Neuroendocrine markers such as Syn and CgA in intrathyroidal thymic carcinoma are also expressed especially for neuroendocrine carcinoma subtypes. In PubMed, intrathyroidal thymic carcinoma lesions were positive for Syn in 18 cases (40.0%, 18/45), CgA in 10 cases (25.6%, 10/39), neuron‐specific enolase (NSE) in 5 cases (17.2%, 5/29), and negative for CD56 in all reported cases (0%, 0/9) . According to Yamazaki et al, the expression of neuroendocrine markers in intrathyroidal epithelial thymoma (ITET)/CASTLE also support the idea that this thyroid carcinoma is of thymic origin because neuroendocrine markers have been reported to be positive in thymic carcinoma in a focal or dispersed distribution.…”

“…Based on 23 literature (101 cases) of intrathyroidal thymic carcinoma described in PubMed, these tumors often show immunoreactivity for CD5 (94.6%, 88/93), CD117 (97.7%, 43/44), while being negative for TTF‐1 (1.2%, 1/82), TG (0%, 0/82), and CT (0%, 0/52) . Other reported markers, such as p63 (100%, 43/43), high‐molecular‐weight cytokeratin (HMWK) (100%, 20/20), Pax‐8 (100%, 10/10), p53 (100%, 20/20), Bcl‐2 (96.43%, 27/28), EGFR (93.75%, 15/16), CEA(67.7%, 21/31), and CK5/6(64.7%, 21/31) are also positive in intrathyroidal thymic carcinoma. The Ki‐67 proliferation index is frequently low .…”

“…Other reported markers, such as p63 (100%, 43/43), high‐molecular‐weight cytokeratin (HMWK) (100%, 20/20), Pax‐8 (100%, 10/10), p53 (100%, 20/20), Bcl‐2 (96.43%, 27/28), EGFR (93.75%, 15/16), CEA(67.7%, 21/31), and CK5/6(64.7%, 21/31) are also positive in intrathyroidal thymic carcinoma. The Ki‐67 proliferation index is frequently low . CD5, CD117, and Ki‐67 are very useful when intrathyroidal thymic carcinoma is suspected in the presence of limited cytological material.…”

Paraneoplastic pemphigus associated with metastatic lymphoepithelioma-like carcinoma originating from the thyroid gland

“…Overall, 16% of PNP cases had nonhaematological neoplasms, including tumours with either epithelial (8·6%) or mesenchymal (6·2%) origin . Lymphoepithelioma‐like carcinoma (LELC) describes a group of tumours with histological features identical to undifferentiated nasopharyngeal epithelial tumours that occur outside the nasopharynx . Although LELC has been observed in many organs, primary LELC of the thyroid gland is extremely rare.…”