Intra thyroid thymic carcinoma: A case report and literature review

Abstract

Introduction and importance: Intrathyroid thymic carcinoma (ITC) is a malignant epithelial tumor with thymic differentiation within the thyroid gland. Its frequency is up to 0.15 % of all malignant thyroid tumors. It is frequently a low-grade tumor. The clinical status is often misleading to other more advanced tumors like cervical lymph node metastasis of nonkeratinizing squamous cell carcinoma, undifferentiated variant, dedifferentiated carcinoma, and medullary carcinoma of the thyroid.

Case preparation: The patient came to us with the diagnosis of cervical lymph node metastasis of undifferentiated carcinoma. This patient was first diagnosed with cervical lymph node metastasis in the previous hospital. After having an ITC diagnosis, the patient was operated on the rennet of thyroid glands and had a low dose of radio-chemotherapy for recurrent prevention purposes. It is the first case of such a disease diagnosed at our hospital and also the first case reported in Vietnam.

Clinical discussion: ITC is rare and appears similar to all thymic carcinoma variants. The most popular type is squamous carcinoma. Immunohistochemical stains are typical for thymic origin tumors with CD5, CD117 positive. ITC is often negative for monoclonal PAX8 but positive in this case (MRQ-50 clone, Sigma-Aldrich). This finding is an exciting one that should considered.

Conclusion: Reporting the case increases the awareness of the disease, especially among Vietnam Doctors and patients.

Keywords: Case report; Intrathyroid thymic carcinoma; Thyroid cancers.

Fig. 1

Ultrasound and CECT images of the patent: (A) The ultrasound revealed a large solid mass (38x25mm) in the anterior cervical region, with an ill-defined margin to the right thyroid, classified as a TI-RADS 5 thyroid nodule due to the extension of the lesion with some suspicious cervical lymph nodes, which the largest lymph node was 8x5mm in size. (B). On the non-contrast CT-Scanner images, a heterogenous hyperenhancement solid mass was detected at the same region, above the superior border of the manubrium sternum bone, anterior to the trachea, brachiocephalic vein, caudal to the thyroid, and invaded to the right thyroid lobe, with mild infiltration to the surrounding fat tissue. Some suspicious hyper-enhanced lymph nodes (level VI) were detected; the largest one was 14 × 8 mm in size.

Fig. 2

The patient's microscopic features: (A). The tumor was lobulated and separated by thick collagen bundles. The tumor was well-circumscribed and had some satellite nodes (H&E stain, 100×). (B). Oval and round, large tumor cells aggregated in social appearances. They were separated by thick collagen bundles and intermingled with small lymphocytes and plasma cells (H&E stain, 400×). (C). The adjacent lymph node was metastasized by identical tumor cells (H&E stain, 400×). (D) Normal thymic tissues were present adjacent to the thyroid gland (H&E stain, 200×).

Fig. 3

The Immunohistochemical characteristics of the patient: (A) CD5 is robust and diffuse positive (Immunohistochemical stain, 400×). (B) CD117 is moderate and diffuse positive (Immunohistochemical stain, 400×). (C) P63 is strong and diffuse positive (Immunohistochemical stain, 200×). (D) PAX8 is mild and patchy positive (Immunohistochemical stain, 200×). (E), (F) Thyroglobulin and calcitonin are negative (Immunohistochemical stain, 200×).