Soft tissue tumor

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Author: Mikael Häggström [note 1]

Gross processing

Generally sample one slice per centimeter.


A solitary fibrous tumor, an example of spindle cell tumor.

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


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.

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