J Korean Endocr Soc.  2008 Aug;23(4):272-276.

A Case of Carcinoma Showing Thymus-Like Differentiation (CASTLE) in the Thyroid

• Kim EH
• Jeong JY
• Kim EY
• Lee SA
• Kim KM
• Yim JH
• Kim WG
• Kim TY
• Kim SA
• Gong G
• Shong YK
• Kim WB

Abstract

Carcinoma Showing Thymus-Like Differentiation (CASTLE) is a very rare malignant neoplasm of the thyroid, and this resembles lymphoepithelioma or squamous cell carcinoma of the thymus. It originates from ectopic thymic tissue or remnants of the branchial pouches. We recently experienced a case of CASTLE in the thyroid gland of a 61-year-old woman. She presented with an asymptomatic mass in the right thyroid gland and she was diagnosed with 'poorly differentiated carcinoma' of the thyroid by fine needle aspiration cytology (FNAC). Total thyroidectomy was performed for both diagnostic and therapeutic purposes. Histologic examination of the resected tumor showed that the tumor was lobulated with expanding fibrous bands, and it was infiltrated by lymphocytes and plasma cells. The tumor cells had oval, large vesicular nuclei and prominent nucleoli, and the immunohistochemical staining was positive for CD5 and bcl-2, so the patient was diagnosed with thyroid CASTLE. We report here on a case of CASTLE in the thyroid gland treated by surgery and external neck radiation therapy.

Keyword

carcinoma; thymus; thyroid gland

MeSH Terms

Biopsy, Fine-Needle
Carcinoma, Squamous Cell
Female
Humans
Lymphocytes
Middle Aged
Neck
Plasma Cells
Thymus Gland
Thyroid Gland
Thyroidectomy

Figure

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  Fig. 1 Thyroid ultrasonography showed 3.3 × 3.1 × 4.7 cm-sized, well-defined hypoechoic solid mass in lower portion of right lobe of thyroid (A) and 0.4 × 0.4 × 0.4 cm nodule in left thyroid (B). No significantly enlarged lymph node was found in the neck.

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  Fig. 2 The tumor was measured 4.7 × 3.5 × 3.2 cm and was well-defined and firm. The cut surface was creamy yellow to pale pink and granular with focal necrosis and hemorrhage.

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  Fig. 3 (H&E, ×400) The interface of the tumor with the thyroid was smooth and relatively well-demarcated. Broad anastomosing islands of tumor cells were separated by lymphoplasmocyte-infiltrated desmoplastic stroma.

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  Fig. 4 (H&E, ×400) The tumor cells had indistinct border and eosinophilic cytoplasm. The nuclei are oval and pale to vesicular with small distinct nucleoli. Small lymphocytes and plasma cell infiltrate in the tumor islands (lower field).

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  Fig. 5 Immunostainigs for CD5 and Bcl-2 of the resected tumor showed tumor cells with strong positive staining.

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