EWSR1-SMAD3-positive fibroblastic tumours are benign mesenchymal neoplasms with different morphologies and a provisional name that have been just recently characterised (c.2018) 1-4 and added to the WHO classification of soft tissue tumours in 2020 2,3.
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Epidemiology
EWSR1-SMAD3-positive fibroblastic tumours are sporadic soft tissue neoplasms. They appear in a wide age range, with women more commonly affected than men 2.
Diagnosis
The diagnosis of EWSR1-SMAD3-positive fibroblastic tumours is established by location, histological, immunohistochemical, and molecular criteria 1.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of tumours: soft tissue and bone (5th edition) 2:
small acral tumours of the skin and subcutaneous tissue
a zonal pattern of a hyalinized acellular centre and fascicular spindle cells in the periphery
immunoreactivity to ERG
The following diagnostic criterion is desirable 2:
EWSR1-SMAD3 fusion
Clinical presentation
EWSR1-SMAD3-positive fibroblastic tumours usually present as painless, small, superficial nodules in an acral location in the hands and/or feet 1,3.
Pathology
EWSR1-SMAD3-positive fibroblastic tumours are characterised by a zonal morphology of intersecting cellular fascicles composed of monomorphic spindle cells and hypo to acellular hyalinised areas 1-4.
Aetiology
The aetiology of those tumours is currently unknown 2.
Location
EWSR1-SMAD3-positive fibroblastic tumours are most commonly located in the skin or the subcutaneous tissue of the hands and feet 1-4.
Macroscopic appearance
Tumours are characterised by a nodular appearance and are usually of small size (up to 1-2 cm) 1,2.
Microscopic appearance
Histologically EWSR1-SMAD3-positive fibroblastic tumours display the following characteristics 1-4:
acellular hyalinized centre
hypercellular peripheral zone with intersecting cellular fascicles of bland spindle cells
absence of nuclear pleomorphism, hyperchromasia and increased mitotic activity
possibly stippled dystrophic calcification
Immunophenotype
Immunohistochemistry stains show diffuse nuclear reactivity for ERG, but do not express CD34 or smooth muscle actin 1,2,4.
Genetics
Those tumours are characterised by genetic EWSR1-SMAD3 fusions 1.
Radiographic features
At the time of writing, there are only very few reports of the radiological features of this entity 5.
Ultrasound
On ultrasound, the tumours have been characterised by hypoechoic subcutaneous nodules 5.
MRI
The tumour has been described as well-circumscribed small lesions 5.
Signal characteristics
T1: hypointense
T2: hyperintense
Radiology report
The radiological report should include a description of the following:
form, location, and size
tumour margins
relation to muscular fasciae
relationship to local nerves and vessels
Treatment and prognosis
The tumours are benign. Local recurrences are seen upon incomplete excision 1,2.
History and etymology
EWSR1-SMAD3-positive fibroblastic tumours have been first described by the Taiwanese pathologist Yu-Chien Kao and his American and Dutch colleagues Lei Zhang, Yun-Shao Sung, Albert JH Suurmeijer and Cristina R Antonescu 1.
Differential diagnosis
Conditions that can mimic the presentation and/or the appearance of EWSR1-SMAD3-positive fibroblastic tumours include the following:
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