Proliferative fasciitis is a benign, reactive, solid, rapidly progressive, pseudo-sarcomatous cellular proliferation of myofibroblastic soft tissue. Proliferative fasciitis was initially scripted by Chung and Enzinger in 1975 . The mass-forming, subcutaneous cellular proliferation exemplifies a heterogeneous group of benign, myofibroblastic lesions which incorporate nodular fasciitis and proliferative myositis. Proliferative fasciitis is a subcutaneous or fascial, tumour- like fasciitis or an intramuscular myositis exhibiting spindle-shaped cellular proliferation with concurrent emergence of enlarged, basophilic, ganglion-like fibroblasts. Myofibroblasts and fibroblasts configuring proliferative fasciitis recapitulate the cellular component of nodular fasciitis . A disorder of controversial pathogenesis and obscure genetic manifestations, proliferative fasciitis recapitulates sarcomas such as rhabdomyosarcoma or epithelioid sarcoma on account of histological manifestations and rapid tumour progression [2,3].
Proliferative fasciitis is a rapidly progressive, self limiting neoplasm which typically appears within middle aged adults or elderly population between 40 years to 70 years. Proliferative fasciitis is uncommon in children below< 15 years. Paediatric neoplasms of proliferative fasciitis are unaccompanied by spontaneous involution. A specific ethnic or gender predilection is absent [2,3]. Proliferative fasciitis is commonly discerned within upper extremities, forearm, lower extremities, or trunk, in a descending order. Majority of lesions are confined to the fascia or subcutaneous tissue of upper extremities. The neoplasm is infrequently discerned upon the hand .
A clonal aberration (MYH-USP6) with genetic fusion is documented in nodular fasciitis, indicative of a benign, neoplastic origin. Aforesaid chromosomal mutation is absent in proliferative fasciitis which can be contemplated as a reactive, myofibroblastic proliferation with obscure genetic manifestation. It is posited that minor trauma or chronic inflammation can trigger proliferative fasciitis although a history of preceding injury is infrequent [2,3]. Proliferative fasciitis is associated with nonspecific features on imaging; thus a cogent tissue evaluation is necessitated for confirmation.
Proliferative fasciitis represents as a painful, palpable,
oedematous, mobile, pseudo-sarcoma like, firm, tender, non-adherent or non-inflamed soft tissue tumefaction situated within subcutaneous adipose tissue which spares the muscular aponeurotic fascia. Alternatively, the neoplasm can emerge as a painless, reddish, rapidly progressive, papular tumefaction, un-associated with a clinical history of trauma [3,4]. The firm tumefaction can induce flexion of adjacent joints. An estimated two thirds lesions are painful, unlike nodular fasciitis and almost one third neoplasms are misinterpreted as a sarcoma due to rapid tumour progression and bizarre histological features [3,4].
On gross examination, a pale, grey/white elliptical neoplasm of variable magnitude is discerned. Commonly, the tumefaction demonstrates a magnitude of two centimetres to three centimetres. The ill defined, subcutaneous mass may expand along horizontal fascial planes. Paediatric neoplasms demonstrate a well circumscribed, lobulated, firm, grey/ white tumefaction of magnitude varying from 1.5 centimetres to 3 centimetres [3,4]. As proliferative fasciitis is a benign, pseudo-sarcomatous proliferation of myofibroblastic soft tissue, preliminary lesions demonstrate foci of enhanced cellularity and myxoid alterations, akin to nodular fasciitis. On cytological examination, smears are cellular and comprised of spindle-shaped and enlarged cells with abundant cytoplasm, singular or dual eccentric nuclei and macro-nucleoli [3,4]. The neoplasm demonstrates
proliferation of spindle –shaped, myofibroblasts intermingled
within a variably myxoid and collagenous stroma. Additionally,
enlarged, polygonal, ganglion-like myofibroblasts are observed,
typically incorporated with abundant basophilic or amphophilic
cytoplasm, enlarged, vesicular nuclei and prominent nucleoli
[3,4]. The poorly circumscribed neoplasm is composed of plump,
spindle-shaped cells configuring abridged fascicles admixed with
enlarged, ganglion-like cells enmeshed within a fibro-collagenous
stroma. Ganglion-like cells are polygonal or elongated and
imbued with abundant, eosinophilic to amphophilic cytoplasm
with singular or dual eccentric, vesicular nuclei and prominent
nucleoli [5,6]. Characteristically, ganglion-like myofibroblasts
intermixed with spindle-shaped myofibroblasts comprise of a
biphasic, cellular population. The neoplasm with poorly defined
margins is composed of plump, fibroblastic or myofibroblastic,
spindle-shaped cells intermixed with enlarged, ganglion-like
cells delineating abundant, amphophilic or basophilic cytoplasm,
spherical, singular or multiple, vesicular nuclei and prominent
nucleoli. Enveloping tumour stroma is collagenous or myxoid and
frequently depicts foci of myxoid-cystic degeneration along with
arborizing vascular configurations. Mitotic figures are variable
and commonly discerned although atypical mitosis is absent
[4,5]. Paediatric proliferative fasciitis is a lobular, non infiltrative
neoplasm with a solid attern of tumour evolution, enhanced
cellularity, enhanced mitotic activity with elevated proportion
of myxoid to collagen stroma. The essentially cellular, paediatric
neoplasm delineates a dissemination of prominent, ganglionlike
cells recapitulating rhabdomyoblasts. Cellular and nuclear
pleomorphism, mitotic figures and an intermingling of acute
inflammatory cells with focal tumour necrosis is observed. Mature
fibroblasts are minimal to absent. Tumour perimeter is pushing, in
contrast to an infiltrative perimeter observed in adult neoplasms
As paediatric tumefaction manifests foci of acute inflammation,
tumour necrosis with exuberant mitosis, a misinterpretation as a
sarcoma may be incurred. Proliferative fasciitis and proliferative
myositis are identical in histology although appear in diverse
locations. Upon ultrastructural examination, tumour cells of
proliferative fasciitis demonstrate lack of cross striations or
features of skeletal muscle differentiation [4-8]. (Figures 1-8).
Spindle-shaped tumour cells are immune reactive to smooth
muscle actin (SMA), muscle specific actin (MSA) and focally
immune reactive to CD68. Ganglion-like cells are immune
reactive to vimentin and inconsistently immune reactive to actin
. The neoplasm is immune-non reactive to cytokeratin, S100
protein, desmin, myogenin, β-catenin, h-caldesmon or CD34 [3,4].
Aforesaid pattern of immune reactivity is identical to immune
staining denominated by nodular fasciitis and proliferative
Proliferative fasciitis mandates a segregation from
i. Giant cells tumour of tendon sheath (GCTTS) which
requires a segregation on account of tumour location and
contiguity with flexor tendon. Giant cell tumour of tendon sheath
displays a lobular tumour architecture with polymorphous
cellular composition of enlarged, histiocytoid cells with abundant
eosinophilic cytoplasm, eccentric nucleus and prominent
nucleolus. Intracytoplasmic hemosiderin or pigment deposition
circumscribing enlarged, histiocytoid cells is discerned. Foamy
or hemosiderin laden histiocytes are intermixed with osteoclastlike
giant cells. Encompassing stroma is sclerotic and collagenous
ii. Ganglioneuroma is composed of proliferation of spindleshaped
cells, akin to neurofibroma. Incorporated ganglion cells
and spindle-shaped cells are immune reactive to neural markers
such as S100 protein.
iii. Nodular fasciitis is composed of myxoid or collagenous
matrix, foci of cystic degeneration, spindle-shaped or stellate cells
with loose, fascicular or storiform pattern and prominent mitosis.
Disseminated lymphocytes, histiocytes and osteoclast-like giant
cells are observed although ganglion-like cells are minimal to
iv. Proliferative myositis is a morphologically similar
neoplasm although located within intramuscular sites .
Paediatric proliferative fasciitis requires a separation from
pertinent sarcomas such as rhabdomyosarcoma and epithelioid
v. Rhabdomyosarcoma demonstrates rhabdomyoblasts
which may depict cross striations or simulate ganglion -like
cells. Spindle-shaped cellular component may appear malignant
and depicts cellular or nuclear atypia. The neoplasm is immune
reactive to desmin or myogenin [6,7].
vi. Epithelioid sarcoma classically delineates spindleshaped
tumour cells with abundant cytoplasm. Foci of tumour
necrosis or inflammation are discerned. Epithelioid sarcoma
is immune reactive to cytokeratin and exhibits a SMARCB1
chromosomal deletion or mutation [6,7].
vii. Undifferentiated sarcoma exhibits an enlarged tumour
mass composed of spindle-shaped cells with nuclear atypia and
cellular or nuclear pleomorphism, atypical mitotic figures and
frequently discerned foci of tumour necrosis [6,7].
Additionally, proliferative fasciitis necessitates a demarcation
from fibroma of tendon sheath, schwannoma or leiomyoma.
Paediatric proliferative fasciitis requires a distinction from
reticulohistiocytoma, xanthogranuloma or epithelioid
Upon plain radiography, bony lesions of proliferative fasciitis
demonstrate a periosteal reaction. Adoption of singular plain
radiography may be unsatisfactory for appropriate tumour
discernment . Ultrasonography exhibits a spherical, well
circumscribed, soft tissue mass or a tumefaction of variable
magnitude with circumscribing soft tissue oedema. Colour
Doppler displays an echogenic, centroidal tumour zone
with an absence of visible signal, a hypoechoic rim and mild
vascularization of the nodule [7,8]. Magnetic resonance imaging
(MRI) delineates a soft tissue mass situated upon extraneous
surface of muscular superficial fascia. Upon T1 weighted imaging,
tumefaction is homogenously isointense as compared to skeletal
muscle. Upon T2 weighted, fat- suppressed imaging, neoplasm
demonstrates a heterogeneous, peripherally intense signal
[6,8]. Fat-suppressed T1 weighted imaging following contrast
administration demonstrates an attenuated rim enhancement
along with enhancement of miniature tumour zones concurrent
with microvascular zones delineating enhanced signal intensity
upon T2 weighted imaging. Peripheral soft tissue oedema and
moderate tenosynovitis of abutting joints and flexor tendons is
exemplified. Magnetic resonance imaging (MRI) can delineate
an elliptical tumour mass situated between flexor tendons. The
benign, non infiltrative neoplasm typically depicts an absence of
diffusion- restriction upon diffusion- weighted imaging and lack
of spontaneous retrogression [6,8].
Surgical exploration demonstrates a tumefaction arising from
tendon sheaths of deep-seated flexor muscles. Comprehensive or
localized surgical extermination of the neoplasm is an optimal
treatment strategy. As adoption of a fine needle or core needle
biopsy may be accompanied by tumour involution, conservative
management is advocated for lesions confined to the extremities.
Postoperative clinical course is usually uneventful with immediate
termination of symptoms. Localized tumour reoccurrence
is usually absent. However, localized surgical excision is
recommended for tumour reoccurrence [7,8].