Picture560 yo M w/ generalized LAD & mediastinal mass. EBUS-FNA of R level 2 mediastinal LNs.

What's the underlying condition?

A. Large cell anaplastic lymphoma
B. Thyroid tissue
C. Thymic cyst
D. Benign mesothelium



B. Thyroid tissue

This is thyroid tissue with cystic degeneration. Thyroglobulin and TTF immunostains confirm the thyroid origin of this material. The differential diagnosis includes a retrosternal goiter vs. metastatic thyroid carcinoma. Of note, there is no lymphoid tissue in the background nor there changes that suggest papillary carcinoma. Still, however, this would be considered metastatic carcinoma replacing the lymph node entirely and undergoing follicular differentiation, even if the primary were papillary carcinoma.

Contributed by: Isam Eltoum