Be. Halliday et al., DIAGNOSTIC UTILITY OF MIC-2 IMMUNOCYTOCHEMICAL STAINING IN THE DIFFERENTIAL-DIAGNOSIS OF SMALL BLUE CELL TUMORS, Diagnostic cytopathology, 19(6), 1998, pp. 410-416
Ewing's sarcoma (ES) and peripheral neuroectodermal tumor (PNET) ale c
onsidered irt the differential diagnosis of small round blue cell tumo
rs of infancy and childhood which includes neuroblastoma, rhabdomyosar
coma and malignant lymphoma. Fine-needle aspiration diagnosis of these
neoplasms can be particularly difficult when the neoplasms are compos
ed of poorly differentiated cells or fail to produce a stroma. MIC-2 i
s a highly sensitive and specific marker for the PNET/ES group of neop
lasms and has been studied extensively in surgical pathology. Other sm
all blue cell neoplasms including rhabdomyosarcoma, blastemal Wilm's t
umor and lymphoblastic lymphoma have also shown positivity but the sta
ining reactions are usually weak and focal. The utility of this marker
in the differential of small blue cell neoplasms in cytologic materia
l has not been examined. Twenty cases of small blue cell neoplasms obt
ained by fine-needle aspiration (FNA),I ere studied. MIC-2 antibody,wa
s applied retrospectively to formalin-fixed cell black material and de
stained alcohol-fired and air-dried cytologic preparations. These case
s include primitive neuroectodermal tumor (five cases), Ewing's sarcom
a (two cases), neuroblastoma (four cases), Wilms's armor (four cases),
lymphoblastic lymphoma (two cases), and small-cell carcinoma (three c
ases). The cases were judged positive when the majority of the cells s
howed cytoplasmic staining. Diffuse cytoplasmic staining was observed
in all seven cases of PNET/ES. Staining could be seen on the destained
air-dried smears (three cases), fired smears (two cases), or the cell
block material (two cases). None of the other 13 small blue cell neop
lasms showed positive staining. We conclude that MIC-2 is a sensitive
and specific marker for the PNET/ES group of neoplasms ill specimens f
rom formalin-fixed cell block, air-dried, and alcohol-fixed cytologic
material and is useful in the differential diagnosis of small blue cel
l tumors. (C) 1998 Wiley-Liss,Inc.