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 结果：考虑为Primitive_Myxoid_Mesenchymal_Tumor_of_Infancy  婴儿原始黏液性间叶肿瘤。本例经澳太中心软组织学会主席Allen教授会诊。

Gross Pathology
The six primary tumors were unencapsulated and
had a multinodular but demarcated appearance with
focal infiltrative growth. The cut surface was white with
fleshy central areas and a firm periphery. Tumor diameter
ranged from 2.5 to 15.0 cm, with a mean of 8.8 cm.
Light Microscopy
All tumors were characterized histologically by a
diffuse growth of primitive spindled, polygonal, and
round cells in a myxoid background (Figs. 1A–D). The
tumor cells were often arranged in a vaguely nodular
pattern with a peripheral collagenized stroma and greater
cellularity at the periphery. Cellularity was low to
moderate. A delicate vascular network with a lacy
appearance was seen in many areas. Medium-sized
arterioles and venules surrounded by a cuff of densely
packed tumor cells were randomly distributed within the
tumors. The tumor cells had bland uniform nuclei with
even chromatin, inconspicuous nucleoli, and variable
amounts of pale eosinophilic to clear vacuolated cytoplasm
(Fig. 1E). In some areas, the vacuolated mesenchymal
cells were arranged in small aggregates. An Alcian
blue stain in 1 case demonstrated cytoplasmic acid mucins
in the vacuolated cells. Highly cellular areas were located
at the periphery of tumor nodules and were composed of
spindle cells arranged in bundles or fascicles with a focal
herringbone pattern (Fig. 1F). Infiltrative growth into

adjacent soft tissue was noted in 3 cases (Fig. 1G). In
three tumors, small cystic spaces were noted and were
lined by tumor cells and contained finely granular
eosinophilic material with a degenerative appearance
(Fig. 1H). Necrosis was identified in 1 case. An
inflammatory infiltrate was absent to sparse. The mitotic
rate varied from less than 1 to 10 mitoses per 10 high
power fields, with a mean of 4 mitoses per 10 high power
fields. No atypical mitoses were observed.
In 2 cases, slides were available from recurrences.
The recurrent tumors had increased cellularity and
increased cellular atypia in comparison with the original
tumors. The recurrent tumor cells were sometimes
elongated or epithelioid and arranged in clusters or
slender fascicles had pale to clear cytoplasm, and had
darker chromatin and more prominent nucleoli.
Immunohistochemistry
Results of immunohistochemical stains are summarized
in Table 2. The tumors showed diffuse reactivity
for vimentin and no reactivity for smooth muscle actin,
muscle specific actin, desmin, S-100 protein, myogenin,
cytokeratin, or bcl-2. Two cases showed indistinct weak
cytoplasmic CD99 reactivity. CD31 and CD34 stains
highlighted the delicate vascular background (Fig. 2) but
did not decorate tumor cell.
Ultrastructural Findings
Electron microscopy was available in 3 cases. All
showed a homogeneous population of poorly differentiated
fibroblasts with nuclei characterized by coarsely
distributed chromatin and cytoplasm devoid of intermediate
filaments, but with Golgi apparatus, free ribosomes,
scanty rough endoplasmic reticulum, and rare
hemidesmosomes and lysosomes (Fig. 3). The tumor cells
were noncohesive and embedded in a collagen-containing
matrix.
Molecular and Cytogenetic Results
Case nos. 1, 2, 3, and 6 were negative for the ETV6-
NTRK3 gene fusion by RT-PCR (2 cases with frozen
tissue and 2 cases with paraffin-embedded samples).
Cytogenetic analysis of tumor tissue from case no. 1
revealed 46, X der (Y)t(Y;9)(q12;p11) der (9)t(3;Y;9)
(p13;q12;p11) or t(3;9)(p12;p11), der (18)t(1;18)(q12;q23).
Cytogenetic analysis of tumor tissue from case no. 2
showed a 46, XY karyotype.

其实是挺好的病例，怎么没人回复，讨论讨论呢？本例是国外专家会诊后才得出的结论，我们也是不认识。

希望大家热烈讨论，明天我会把结果和文献上传，大家一起学习啊！