An open right-sided neck biopsy was performed.

Histology:

MACROSCOPIC DESCRIPTION: Two specimens received.

Right neck mass 1: Multiple irregular cream necrotic pieces of tissue measuring 20x15x4 mm in aggregate.

Right neck mass 2: Multiple tan to necrotic pieces of tissue measuring 15x15x8 mm in aggregate.

MICROSCOPIC DESCRIPTION: Both biopsies show similar appearances, comprising fibroadipose tissue that is infiltrated by a largely necrotic tumor comprising sheets of discohesive and pleomorphic malignant epithelial cells with cytoplasmic vacuolation and mucoid material in the background.

Immunohistochemistry: AE1/AE3+, CD3-, CD20-, CD30-, TTF1-, CK7 focal weak+, CK20-, CK5/6-, PSA-, thyroglobulin-, BRAF V600E-, ALK-.

The features are those of a poorly differentiated carcinoma that would be compatible with anaplastic thyroid carcinoma.

DIAGNOSIS: Undifferentiated carcinoma, compatible with anaplastic thyroid carcinoma.