Ear, Nose & Throat Journal2023, Vol. 102(4) 263–267© The Author(s) 2022Article reuse guidelines:sagepub.com/journals-permissionsDOI: 10.1177/01455613221145287journals.sagepub.com/home/ear
Migration of the embryonic thymus is thought to be the basis for the formation of ectopic thymic tumors. Thymic ectopy may be a result of the abnormal migration of the third or fourth branchial cleft to the anterior mediastinum during weeks 5–6 of embryonic development. However, ectopic thymic carcinoma has highly nonspecific histologic features and occurs in variable and unpredictable locations making it difficult to diagnose. However, the clinical diagnosis and treatment should not overlook the possibility of ectopic thymic tumors. Here, we report a case of ectopic thymic carcinoma diagnosed as thyroid cancer before surgery occurring in a location consistent with current assumptions. Furthermore, we briefly review the literature on ectopic thymic carcinoma and discuss current diagnostic and treatment approaches.
Keywordsectopic thymus, thymic carcinoma, thyroid carcinoma, pathological diagnosis, immunohistochemical
Thymic ectopia may be a result of the abnormal migration of the third or fourth branchial cleft to the anterior mediastinum during the 5th–6th weeks of embryonic development. Ectopic thymus tissue can occur in the parotid gland,1 mandible, lateral cervical area,2 thyroid area,3 paratracheal region, pericardium,4 thorax,5 and pleura.6 The cervical region is the most common site for ectopic thymic neoplasms. Neoplastic and non-neoplastic lesions can occur in the ectopic thymic tissue. Adenomas are the most predominant tumor lesions, while adenocarcinoma is rare.
Here, we report a case of ectopic thymic carcinoma diagnosed as thyroid carcinoma before surgery.
On examination, a mass approximately 2 cm in diameter was found on the dorsal side of the left lobe of the thyroid gland in a 66-year-old man. The lump was hard, had poor mobility, and caused no discomfort for the patient. The patient’s family and personal history were unremarkable. A thyroid ultrasound showed that the nodule was adjacent to the left parathyroid gland (Figure 1A), and the lymph nodes in zone II and III of the neck were imaged. A computed tomographic scan of the neck revealed an approximately 2.4 × 1.7 cm tumor/nodule on the dorsal side of the left lobe of the thyroid (Figure 1B). Thyroid function and corresponding antibodies were within normal reference ranges. Cytology of a fine-needle aspiration showed atypical hyperplasia of thyroid epithelial cells and a malignancy could not be excluded. The presumptive diagnosis was a thyroid tumor or lymphoma.
During the operation, gray and yellow irregular tissue was found behind the left thyroid gland adhered to the thyroid lobe and was separate from the mediastinal thymus. The left lobe of the thyroid gland and mass were removed and the sentinel lymph node was negative (Figure 2A). The solid mass measured approximately 2.5 × 1.8 × 1.5 cm, and a section of it was gray and brittle (Figures 2B and 2C). Intraoperative frozen sections showed benign thyroid lesions and a solid mass consistent with squamous cell carcinoma. Postoperative pathological sections verified the nodular goiter (Figure 2D), and no metastasis were found in the central lymph nodes (Figure 2E). The mass was diagnosed as thymic squamous cell carcinoma and was positive for CK, CK19, p63, CD5, CD20, CD117, p53 (60%), and Ki-67 (20%, Figures 2F and 2G).
Our case study describes an asymptomatic neck mass in an older man. Due to its location and cytological results of a fine-needle aspiration, the preliminary diagnosis was a thyroid tumor or lymphoma. However, the postoperative pathological report confirmed that it was a thymic carcinoma. Pathologic and immunohistochemical evidence supported that this thymic carcinoma was caused by abnormal thymic migration during embryonic development.
Thymic cancer can occur at any age but is most commonly seen in adults between the ages of 30–60. Thymic carcinoma has highly nonspecific histological characteristics and is a diagnosis of exclusion that requires a thorough investigation to rule out other malignancies. Because its location is variable and unpredictable, the preoperative diagnosis of ectopic thymic carcinoma is extremely challenging. Ectopic thymic carcinoma of the neck is usually characterized by a painless mass that can easily be confused with thyroid nodules or enlarged lymph nodes due to its location and nonspecific cytology results on fine-needle aspiration. A literature search revealed only a few cases2,3,7-9 of cervical ectopic thymic carcinoma (Table 1). The limited experience in diagnosing and treating such cases makes it crucial to summarize previous cases. From the existing limited number of case reports, the prognosis is relatively good due to postoperative adjuvant therapy. Currently, there are no standardized diagnostic or treatment recommendations for ectopic thymic carcinoma. The current literature shows that specific immunohistochemical markers, especially CD117 and CD5, are helpful in the diagnosis of primary thymic cancer.7,10 The inclusion of ectopic thymic carcinoma in the differential diagnosis of a thyroid region mass and the use of immunohistochemistry after an incisional biopsy, when feasible, are the best ways to obtain the correct preoperative diagnosis of this rare neoplasm. The main treatment approaches for cervical ectopic thymic cancer include surgical resection, neck lymph node dissection, postoperative adjuvant radiotherapy, and chemotherapy.3 Some researchers have suggested that the thymus be removed simultaneously with the ectopic thymic cancer to reduce recurrence.8 Because this disease is rare, there is a lack of sufficient evidence-based guidance to establish common diagnostic and treatment standards. However, the clinical diagnosis and treatment should not disregard the possibility of an ectopic thymic carcinoma.
Data curation: Wei Wang, Jia-Ying Xu, and Bo-Tao Zhang; Writing – original draft: Wei Wang; Writing – review and editing: Jun Jiang.
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article:This study was supported by the National Natural Science Foundation of China (82070288), the Science & Technology Department of Sichuan Province (2022YFS0627), the Health Commission of Sichuan Province (21PJ100), the Talent Development Project of The Affiliated Hospital of Southwest Medical University (20062).
Written informed consent was obtained from the patient(s) for their anonymized information to be published in this article.
Wei Wang https://orcid.org/0000-0002-5775-8192
Jia-Ying Xu https://orcid.org/0000-0002-9903-8855
Bo-Tao Zhang https://orcid.org/0000-0003-0299-8575
Jun Jiang https://orcid.org/0000-0003-1292-7236
1 The Department of General Surgery (Department of Thyroid Surgery), the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan Province, China
Received: October 14, 2022; revised: November 21, 2022; accepted: November 29, 2022
Corresponding Author:Jun Jiang, The Department of General Surgery (Department of Thyroid Surgery), the Affiliated Hospital of Southwest Medical University, No. 25 Taiping Street, Jiangyang Di, Luzhou, China.Email: jiangjun@swmu.edu.cn
