Cribriform Morular Thyroid Carcinoma: A Rare Case and Associated Uncommon Features

Area of Science:

• Endocrinology
• Oncology
• Pathology

Background:

• Cribriform morular thyroid carcinoma is classified under tumors of uncertain histogenesis.
• This subtype exhibits distinct clinical, histomorphological, and immunohistochemical characteristics compared to papillary thyroid carcinoma.

Observation:

• A 59-year-old female presented with a large left thyroid lobe tumor initially misdiagnosed as medullary thyroid carcinoma via fine needle aspiration.
• Microscopic examination revealed a mixed cribriform and solid morular pattern, lacking papillary nuclear features, with squamoid morules, stromal hyalinization, and calcification.

Findings:

• The tumor measured 9.5 cm, with no evidence of extrathyroidal extension, lymphovascular invasion, or lymph node metastasis.
• Immunohistochemistry showed diffuse strong nuclear positivity for β-catenin, TTF1, PAX8, and estrogen receptor, with focal weak CD5 positivity. Calcitonin, thyroglobulin, synaptophysin, and CDX2 were negative.

Implications:

• This case underscores the importance of recognizing cribriform morular thyroid carcinoma as a distinct entity.
• Understanding its unique histological and immunohistochemical profile is crucial for accurate diagnosis and management.