Thyroid Carcinoma Showing Thymus-like Differentiation (CASTLE): A Case Report

Area of Science:

• Endocrinology
• Oncology
• Pathology

Background:

• Carcinoma showing thymus-like differentiation (CASTLE) is a rare, low-grade thyroid malignancy.
• Clinical and imaging features of CASTLE are non-specific, mimicking other thyroid lesions.
• Definitive diagnosis relies on immunohistochemical examination, particularly CD5 positivity.

Observation:

• A rare case of CASTLE compressing the trachea in a 50-year-old female is presented.
• Initial misdiagnosis as undifferentiated thyroid carcinoma led to unsuccessful treatment.
• The patient underwent successful radical resection after a second medical opinion.

Findings:

• Pathological and immunohistochemical examinations confirmed CASTLE diagnosis.
• Post-surgical follow-up showed no local recurrence at 6 months and 2 years.
• Complete tumor removal and low infiltration correlate with better survival.

Implications:

• Accurate diagnosis of CASTLE requires expertise in histology and CD5 immunohistochemistry.
• Early and correct diagnosis is vital for appropriate management and improved patient outcomes.
• CASTLE's indolent nature and favorable prognosis depend on complete resection and limited tumor infiltration.