PMC149357_01
An axial computed tomography scan with contrast medium showing a 3.4 x 2.5 cm mass on the right parotid gland (arrows).
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F1
No pathological lymph nodes were identified (Fig. 1).
Left panel (enlargement 10x): undifferentiated carcinoma with poorly squamous differentiation (bottom right) very near to a typical Warthin's tumour (upper left). The arrows indicate the transition zone from a benign to malignant neoplasm. Right panel (enlargement 40x): detail of the malignant area. Hematoxylin and eosin stains.
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F2
The surgical specimen (3.5 x 2.5 x 1 cm) had a well-circumscribed, spherical, soft grey nodule with a few small cysts (a typical WT); the inner portion consisted of a harder yellow mass measuring 1.7 cm that proved to be a poorly differentiated carcinoma (Fig. 2).
Upper panels, hematoxylin and eosin staining. Panel (a) shows a low resolution (5 x) image of the oncocytic transition from typical papillae (asterisk) and a hyperplastic-dysplastic state (cross) to malignant transformation (circle). Panel (b) shows a 10x enlargement of the undifferentiated carcinoma with a few atypical mitoses (arrows). Lower panels, immunohistochemistry anti-cytokeratin staining: panel (c) shows a 10x enlargement of the undifferentiated carcinoma immunoreactive to cytokeratin, and panel (d) a detail (40x) of a very atypical cell with cytoplasmic anti-cytokeratin immunoreactivity.
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F3
The oncocytic epithelial component inside the typical WT showed a hyperplastic-dysplastic change confluent with solid undifferentiated neoplasm (Fig 3a,3b); the malignant epithelial component, which was immunoreactive to an anti-cytokeratin pool (AE1-AE3; Dako), consisted of nests or single cells with a surrounding desmoplastic stroma sometimes infiltrated by small lymphocytes and plasma cells (Fig. 3b,3c).