-
Diagnosis: metastatic Merkel cell
carcinoma.
-
Microscopic description: The tumor
consists of monotonous, small, round and blue cells with very
high N/C ratio and evenly dispersed chromatin. The nucleolus is
inconspicuous. The tumor cells are dyscohesive with focal
vaguely nodular pattern. Abundant mitotic figures are present.
-
Differential diagnosis:
-
T-ALL: young age,
mediastinal mass, TdT+, CD3+.
-
B-ALL: young age, more
common as leukemia form, TdT+, CD10+, CD20+.
-
Metastatic small cell
carcinoma for the lung: CK20-, CK5/6+, TTF+ (50%),
CEA+/-.
-
Small cell melanoma:
S100+, MITF+. MART1+, HMB45+, CK20-.
-
PNET: CD99+, Vimentin+,
CK20-.
-
Merkel cell carcinoma:
CK20+, CK5/6-, p63-, TTF1-, CEA-, S100-, vimentin-, CD45-,
CD117+, Synaptophysin+, chromogranin A+.
|
Tumor |
PanCK |
CK20 |
CK5/6 |
P63 |
TTF1 |
CD99 |
CEA |
S100 |
Melan-A |
Vimentin |
CD45 |
| Merkel cell carcinoma |
+ |
+ |
− |
− |
− |
+/− |
− |
− |
− |
− |
− |
| Metastatic small cell carcinoma (lung) |
+ |
− |
− |
− |
+ |
+/− |
+/− |
− |
− |
− |
− |
| Small cell squamous carcinoma |
+ |
− |
+ |
+ |
− |
− |
− |
− |
− |
+/− |
− |
| Small cell eccrine carcinoma |
+ |
− |
− |
− |
− |
− |
+/− |
+/− |
− |
+/− |
− |
| Small cell melanoma |
− |
− |
− |
− |
− |
+/− |
− |
+ |
+ |
+ |
− |
| Primitive neuroectodermal tumor |
+/− |
− |
− |
− |
− |
+ |
− |
− |
− |
+ |
− |
| Non-Hodgkin's Lymphoma |
− |
− |
− |
− |
− |
+/− |
− |
− |
− |
+/− |
+ |
|
