Eble JN, Sauter G., Epstein JI, Sesterhenn IA - iarc

A
B
Fig. 4.19 Seminoma. A Typical seminoma with pronounced infiltration of lymphocytes. B Granulomatous stromal response.
anaplastic seminoma, or seminoma with
high mitotic index {1805,1809,2603}.
These are not always subdivided into a
separate category of seminoma because
their clinical outcome is similar to classical
seminoma {2542,2946}. However,
some studies indicate that seminomas
with high mitotic counts, higher S-phase
fraction, increased mean nuclear volume,
and aneuploidy have a poorer
prognosis {1778,2780}, higher incidence
of metastasis {817,1122}, and are at a
higher stage at clinical presentation
{1873,2616}. The prognostic significance
of these features, however, remains controversial
{444}.
Seminoma with syncytiotrophoblastic
cells
Tumour giant cells are also seen with
morphological and ultrastructural features
of syncytiotrophoblastic cells (STC)
{2355}. The STCs are usually multinucleate
with abundant slightly basophilic
cytoplasm, and may have intracytoplasmic
lacunae, although some have sparse
cytoplasm with crowded aggregates of
nuclei having a “mulberry-like” appearance.
They may be surrounded by localized
areas of haemorrhage although they
are not associated with cytotrophoblastic
cells, and do not have the features of
choriocarcinoma. These cells stain for
hCG and other pregnancy related proteins
and cytokeratins {550}.
Up to 7% of classical seminomas have
recognizable STCs, however, hCG positive
cells may be identified in up to 25%
of seminomas {1202,1803} some of
which are mononuclear cells.
The presence of hCG positive cells is frequently
associated with elevated serum
hCG (typically in the 100s mIU/ml) {1033}.
Higher levels may indicate bulky disease
but possibly choriocarcinoma {1123,2806}.
Seminomas with STCs or elevated serum
hCG do not have a poorer prognosis in
comparison to classic seminoma of similar
volume and stage {1123,2806}. Other giant
cells are frequently seen in seminomas
and may be non neoplastic Langhans
giant cells associated with the inflammatory
stromal response.
Immunoprofile
Placental alkaline phosphatase (PLAP) is
seen diffusely in 85-100% of classical
seminomas with a membranous or perinuclear
dot pattern {444,2664} and persists
in necrotic areas {780}. C-Kit
(CD117) has a similar established incidence
and distribution {1478,2616}.
VASA is extensively positive {2929}.
Angiotensin 1-converting enzyme (CD
143) resembles PLAP and CD117 in distribution
{2618} but is not in widespread
diagnostic use. In contrast, pancytokeratins
(Cam 5.2 and AE1/3) and CD30 are
less frequently seen and usually have a
focal distribution {444,2616}. In differential
diagnostic contexts the following are
helpful:
Seminoma versus embryonal carcinoma
– a combination of negative CD117 and
positive CD30 {1478,2664}, widespread
membranous pancytokeratins, CK8, 18
or 19 {2664}, support embryonal carcinoma;
classical seminoma versus spermatocytic
seminoma – widespread PLAP
indicates the former.
Differential diagnosis
Seminomas are occasionally misdiagnosed
{1463,2353}. Rarely, the distinc-
A
Fig. 4.20 Seminoma. A Seminoma with dense cytoplasm and pleomorphic nuclei. B High mitotic rate seminoma.
B
Fig. 4.21 Seminoma with syncytiotrophoblasts.
Note the association with haemorrhage.
232 Tumours of the testis and paratesticular tissue