Morule with biotin-containing intranuclear inclusions in thyroid carcinoma

Area of Science:

• Endocrinology
• Oncology
• Pathology

Background:

• Thyroid carcinoma encompasses various subtypes, with papillary carcinoma being the most common.
• Morules and squamous metaplasia are uncommon findings in thyroid tumors, requiring detailed clinicopathological analysis.
• Understanding the distinct characteristics of these lesions is crucial for accurate diagnosis and prognosis.

Purpose of the Study:

• To compare the clinicopathological and immunohistochemical features of morules and squamous metaplasia in thyroid carcinoma.
• To investigate the potential prognostic implications of these distinct cellular changes.

Main Methods:

• Retrospective review of 1060 thyroid carcinoma cases.
• Clinicopathological analysis of morules and squamous metaplasia.
• Immunohistochemical staining for specific markers (biotin, Ulex Europaeus agglutinin I, bovine muzzle epidermal keratin).
• Ultrastructural examination of optically clear nuclei (OCN).

Main Results:

• Morules were identified in 0.47% of cases (5/1060), predominantly in younger females with papillary or follicular carcinoma.
• Squamous metaplasia was found in 3.0% of cases (32/1060), affecting a wider age range and mostly associated with papillary carcinoma.
• Morules showed characteristic 'optically clear nuclei' (OCN) with intranuclear biotin, positive for Ulex Europaeus agglutinin I (UEA-l), and negative for bovine muzzle epidermal keratin (EK).
• Squamous metaplasia lacked OCN, was negative for UEA-l, and positive for EK.
• Prognostic data indicated varied outcomes for patients with morules and a higher rate of mortality and recurrence in those with squamous metaplasia.

Conclusions:

• Morules and squamous metaplasia represent distinct entities within thyroid carcinoma, differing significantly in their occurrence, cellular morphology, and immunohistochemical profiles.
• The presence of OCN and specific marker expression (UEA-l, EK) aids in differentiating these lesions.
• Further research is warranted to fully elucidate the prognostic significance of morules and squamous metaplasia in thyroid cancer.