Although intermediate
trophoblastic tumors (ITTs) are rare forms of trophoblastic
neoplasia, their recognition is important as they require distinct therapeutic approaches. We have noted mixed
trophoblastic tumors, with a combination of
placental site trophoblastic tumor and epithelioid
trophoblastic tumor patterns within the same case, and more frequently a combination of ITT with
choriocarcinoma, which can create difficulty in the classification of these
tumors. The distinction of the ITTs from
choriocarcinoma is important because ITTs do not respond as well to
chemotherapy as
choriocarcinoma. In addition, ITTs can be confused with a variety of
malignant neoplasms, the most common of which is poorly differentiated
carcinoma of the cervix. Immunohistochemistry is one means of identifying
trophoblastic tumors and of distinguishing them from other entities. We investigated the immunophenotype of 15 ITTs, 11
choriocarcinomas, and 10 primary cervical
carcinomas using a panel of
human placental lactogen, p63, CK5/6, CK18,
human chorionic gonadotropin (hCG),
human leukocyte antigen (HLAG), Mel-CAM, (CD146)
carcinoembryonic antigen, CD10,
inhibin, p16, and pan-
keratin. CD10 was positive in all the cases of ITT and
choriocarcinoma.
HLA-G expression was present in 93% of ITTs and all
choriocarcinoma cases. hCG was positive in 87% of ITTs and 100% of
choriocarcinomas. We concluded that a panel consisting of
HLA-G, CD10, and hCG can be very helpful in the identification of the ITTs. Adding CK5/6 to these markers can help to differentiate ITT from primary cervical
carcinoma. However, the distinction of ITTs from
choriocarcinoma cannot be accomplished on immunohistochemical studies, as they have similar immunophenotypes.