Abstract
Carcinoid tumors having distinct paranuclear clear zones seen on hematoxylin and
eosin stain are rare and few cases have been reported in the literature.
Furthermore, primary hepatic carcinoid tumor with a paranuclear clear zone is
extremely rare. We recently experienced a case from a 48-year-old man who
presented a large single mass, 12 cm in largest diameter, in the right lobe of
the liver. Histologically, the tumor revealed characteristic organoid pattern
with central hyaline degeneration. The tumor cells had a prominent paranuclear
vacuolated dear zone. On immunohistochemistry, tumor cells were diffusely
positive for synaptophysin and focally stained for chromogranin A.
Ultrastructural examination revealed paranuclear aggregation of intermediate
filaments and membrane-bound clear vesicles, which corresponded to the
paranuclear vacuolated clear zone.