Undifferentiated Malignant Neoplasm Involving Parotid and Thyroid: Sampling and PAX8 Cross-Reactivity Can Obscure the Diagnosis of Lymphoma

Figure 3

Cell block contained malignant cells expressing pancytokeratin cytoplasmic immunoreactivity and PAX8 nuclear staining but stained negatively with B lymphocyte marker CD20.

(a) Cell block, 200x magnification, H&E stain

(b) Cell block, 400x magnification, pancytokeratin immunostain

(c) Cell block, 400x magnification, CD20 immunostain

(d) Cell block, 400x magnification, PAX8 immunostain