Hepatoid
thymic carcinoma is an extremely rare subtype of primary
thymus tumor resembling “pure” hepatoid
adenocarcinomas with
hepatocyte paraffin 1 (Hep-Par-1) expression. A 53-year-old man presented with
voice change and a
neck mass. Multiple masses involving the
thyroid, cervical and mediastinal
lymph nodes, and
lung were detected on computed
tomography.
Papillary thyroid carcinoma was confirmed by
biopsy, and the
patient underwent
neoadjuvant chemoradiation therapy. However, the anterior mediastinal mass was enlarged after the
treatment whereas the multiple masses in the
thyroid and
neck decreased in size. Microscopically, polygonal
tumor cells formed solid sheets or trabeculae resembling
hepatocytes and infiltrated remnant
thymus. The
tumor cells showed immunopositivity for
cytokeratin 7,
cytokeratin 19, and Hep-Par-1 and negativity for α-
fetoprotein. Possibilities of
germ cell tumor,
squamous cell carcinoma, and
metastasis of
thyroid papillary carcinoma were excluded by
immunohistochemistry. This
report on the new subtype of
thymic carcinoma is the third in English
literature thus far.