Sclerosing epithelioid fibrosarcoma

Last revised by Joachim Feger on 22 Oct 2022

Sclerosing epithelioid fibrosarcomas are rare slow-growing malignant fibroblastic soft tissue neoplasms pictured by a dense sclerotic hyalinized stroma with cords and areas of epithelioid fibroblasts.

The tumor is rare and usually found in the middle-aged and elderly population. There is no gender predominance 1.

Sclerosing epithelioid fibrosarcomas are related to low-grade fibromyxoid sarcomas.

The diagnosis of sclerosing epithelioid fibrosarcomas is established by histological, immunohistochemical and molecular genetic criteria 1.

Diagnostic criteria according to the WHO classification of tumors: soft tissue and bone (5th edition) 1:

  • epithelioid cells in a dense sclerotic collagenous background, organized in nests, cords or sheets
  • clear diffuse MUC4 positivity in most cases

The following molecular genetic criterion is desirable in selected cases:

  • EWSR1-CREB3L1 gene or other rearrangements

The typical complaint is a soft tissue mass. The duration varies but more than 30% of patients report a recent enlargement or pain 1.

Sclerosing epithelioid fibrosarcomas are malignant tumors characterized by cords or nests of epithelioid cells within a dense hyalinized stroma 1.

The etiology of sclerosing epithelioid fibrosarcomas is unknown.

Sclerosing epithelioid fibrosarcomas are most often found in the deep soft tissues in the following locations 1-3:

  • upper or lower extremities
  • limb-girdle
  • trunk
  • head and neck

Rare locations include the pelvis, retroperitoneum, abdominal cavity or bones 1

Grossly sclerosing epithelioid fibrosarcomas are firm, lobular well-demarcated tumors of grey-white color. They usually involve the deep muscles and muscular fascia or adhere to the periosteum and occasionally might involve the bone 1-3. There might be calcifications 1.

The microscopic appearance of sclerosing epithelioid fibrosarcomas includes the following 1,2, 6:

  • nests, cords or sheets of monomorphic epithelioid cells with scant clear to eosinophilic cytoplasm in a hyalinized sclerotic extracellular matrix
  • margins can infiltrate into adjacent muscle fascia or periosteum
  • occasional alveolar pattern

Immunohistochemistry stains often express MUC4 and vimentin and might express EMA, CD99 or smooth muscle actin 1,3. They are usually negative for keratin 1,3.

Sclerosing epithelioid fibrosarcomas can demonstrate EWSR1-CREB3L1 gene fusions 1,3.

Descriptions of imaging findings of sclerosing epithelioid fibrosarcomas are few in the literature 4-7.

There have been descriptions of punched-out osteolytic appearance with a sclerotic rim 2.

CT findings in sclerosing epithelioid fibrosarcomas have been reported as heterogeneous soft-tissue masses. In the case of osseous involvement, they have been described as osteolytic lesions with bone destruction but none or only slight periosteal reaction 4,5.

Only a few descriptions are available in the literature. Lesions might be well-circumscribed and sharply demarcated and associated with peritumoral edema or in the case of osseous involvement bone marrow edema 4-6.

Signal characteristics of different single cases were reported as follows 4-6:

  • T1: hypo- to isointense to muscle
  • T2: mixed-signal intensity with irregular hypointense areas
  • T1 C+ (Gd): heterogeneous and perilesional enhancement

FDG uptake is assumed to correlate with grade 7.

The radiological report should include a description of the following features:

  • form, location and size
  • tumor margins
  • relation to adjacent bones and the muscular fascia
  • relationship to local nerves and vessels
  • relationship to other organs

Recurrences and metastases in sclerosing epithelioid fibrosarcomas are common and occur in about 50% of the cases. The most common sites for metastasis are the lung, pleura, bone and brain 1-4.

Sclerosing epithelioid fibrosarcoma was first described by the American-Swedish pathologists Jeanne M Meis-Kindblom and Lars-Gunnar Kindblom and the Austrian-American pathologist Franz Michael Enzinger in 1995 2-8.

Conditions that can mimic the appearance of sclerosing epithelioid fibrosarcomas include 1-7:

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