Case 28 - Discussion

Uploaded: 2007-03-01, Updated: 2007-06-24

IMMUNOHISTOCHEMISTRY:
Vimentin - positive
CD56 (neural marker) - positive
Cytokeratin AE1/3 - negative
Desmin - negative
SMA - negative
CD57 - negative
S100 - negative
CD68 - weak focal positivity

Microscopic Description
Several sections of tumor are sampled for microscopic examination. The tumor is present in the vicinity of large nerves. It is composed of spindle cells that, in some areas, are arranged in densely packed short fascicles, but in other areas display loose arrangement within fibrous stroma or within myxoid background. Some areas of tumor show extreme pleomorphism due to the presence of large hyperchromatic nuclei and tumor giant cells (for example, slide A4 and A18). Geographic areas of necrosis are also identified. The tumor is focally present at the inked resection margin (slide A11). The histologic and immunostaining pattern (CD56 and vimentin positive) support the diagnosis of malignant peripheral nerve sheath tumor.

ELECTRON MICROSCOPY:

Ultrastructurally, the tumor cells are spindle-shaped, some of which show long, intertwining cell processes. There is focal basal lamina formation. The nuclei are pleomorphic with many indentations; generally one large nucleolus is seen within the tumor cells. The nuclear to cytoplasmic ratio is high. the cytoplasm contains abundant rough endoplasmic reticulum, and some mitochondria and lysosomes. (By SR/WJH)
ULTRASTRUCTURAL IMPRESSION: Consistent with malignant peripheral nerve sheath tumor.
 

Diagnosis:

SOFT TISSUE, RETROPERITONEUM, EXCISION:
- High grade sarcoma, consistent with malignant peripheral nerve sheath tumor.
- Histopathologic grade: 3/3 (FNCLCC grading system).
- Maximum tumor dimension: 14.0 cm.
- Tumor is focally present at inked resection margin.
By MC/PS

Malignant peripheral nerve sheath tumor