Superficial CD34-positive fibroblastic tumours (SCPFT) or PRDM10-rearranged soft tissue tumours are rare low-grade mesenchymal neoplasms of the dermis and subcutis 1-3 that have been just recently added to the WHO classification of soft tissue tumours in 2020 2,3.
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Epidemiology
Superficial CD34-positive fibroblastic tumours are rare with less than 200 reported cases in the literature 4,5. They have been found in a wide age range ranging from 8 to 76 years and median age of 33 years (less than 10% of patients ≤18 years of age). Men are slightly more commonly affected 4.
Diagnosis
The diagnosis of superficial CD34-positive fibroblastic tumours is established by location, histological and immunohistochemical criteria 1,2.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of tumours: soft tissue and bone (5th edition) 2:
superficial location
abundant granular to glassy eosinophilic cytoplasm
very low mitotic count but considerable nuclear pleomorphism
diffuse immunoreactivity to CD34 and frequent positivity of cytokeratins
Clinical presentation
Superficial CD34-positive fibroblastic tumours usually present as painless longstanding slow-growing dermal or subcutaneous masses usually <5 cm in size 1,3.
Pathology
Superficial CD34-positive fibroblastic tumours are superficial sheet-like or fascicular proliferation of spindle and epithelioid cells with remarkable cell atypia but insignificant mitotic activity 1-4.
Aetiology
The aetiology of superficial CD34-positive fibroblastic tumours is currently unknown 2.
Location
Tumours are most commonly located in a suprafascial location of the extremities more often in the lower ones including the thigh, arms, buttocks, shoulder and vulva 1,2.
Macroscopic appearance
Macroscopically tumours are well-defined with a yellow-tannish colour, at times gelatinous appearance and a firm consistency 1,2.
Microscopic appearance
Histologically superficial CD34-positive fibroblastic tumours display the following characteristics 1-4:
cellular sheets and fascicles of spindled or epithelioid cells
extensive eosinophilic cytoplasm often with a glassy or granular appearance
compelling nuclear pleomorphism
insignificant mitotic activity
rare necrosis
common mixed inflammatory infiltrates
Immunophenotype
Immunohistochemistry stains express CD34 and are often positive for cytokeratins in up to 70% of cases 1-3.
Genetics
PRDM10 rearrangements have been reported in a subset of several cases 1,2,5.
Radiographic features
At the time of writing, there are only very few reports of the radiological features of this entity 6.
CT
The tumour has been described as well-delineated in one case with weak contrast enhancement. The pictures depicted the entity as a hypodense lesion compared to skeletal muscle 6,7.
MRI
The tumour has been characterised as a well-circumscribed lesion. An internal lobulated appearance has been demonstrated 7.
Signal characteristics
T1: hypointense (mildly hyperintense compared to muscle)
T2: hyperintense
T1 C+ (Gd): mild enhancement
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
local lymph nodes
Treatment and prognosis
Management consists of surgical excision. Prognosis is excellent with very rare cases of lymph node metastases and rare local or distant recurrences 1-4.
History and etymology
Superficial CD34-positive fibroblastic tumours were first described by the American pathologists Jodi M Carter, Sharon W Weiss, Konstantinos Linos, David J DiCaudo and Andrew L Folpe in 2013 1,4.
Differential diagnosis
Conditions that can mimic the presentation and/or the appearance of superficial CD34-positive fibroblastic tumours include the following:
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