Soft tissue tumor
If it appears fatty, gross and evaluate as a lipomatous tumor.
Generally sample one slice per centimeter.
In case of spindle cell tumors (having elongated nuclei), the following features may help to roughly classify the tumor:
- Pointed on both ends: True fibroblastic tumors
- Pointed on one end and blunted on the other ("bullet-shaped"): Neural/nerve sheath tumors (see section below)
- Blunted on both ends ("cigar-shaped"): Smooth muscle tumor
- Triangular: Myofibroblastic
In uncertain cases, the following immunohistochemistry markers are usually helpful:
- CD34, indicating a solitary fibrous tumor
- S100, indicating a neural or nerve sheath tumor (see section below)
- Desmin, indicating a muscular tumor (skeletal muscle or Smooth muscle tumor)
- Beta catenin, indicating fibromatosis
Also consider a sarcoma as a differential diagnosis, and if unsure, have a low threshold for consulting with people with expertise in the matter, as the visual difference between benign and malignant spindle cells is relatively subtle.
Neural or nerve sheath tumors
Further information: Evaluation of suspected malignancies