Nodular
fasciitis was first described in 1955 by Konwaler et al, as Subcutaneous
pseudosarcomatous fibromatosis (fasciitis).
Exact cause of the lesion is not known but it is considered to be a selflimiting reactive process rather than a true neoplasm.
Clinical presentation:
The tumour presents as a rapidly growing nodule (usually present for 1 or
2 weeks), may be associated with tenderness. These are usually solitary
lesions.
Age: Nodular
fasciitis is common in young adults (between 25 and 35 yrs) and less
frequently in infants.
Site: In
adults, these are commonly located in the upper extremities (flexor surface
of the forearm) and the trunk (chest wall and back). In infants, nodular
fasciitis is present in the head and neck region.
Macroscopic appearance: The lesion consists of
nodular, nonencapsulated mass usually less than 3cm in diameter.The cut
surface may show firm and grey white or soft and gelatinous areas.
Subtypes :
- Fascial type-
Poorly circumscribed lesion , extends along the superficial fascia and
interlobular septa of subcutaneous fat .
-Subcutaneous type-
Well circumscribed lesion, extends into the subcutis.
-Intramuscular type-
Well circumscribed lesion , grows into the skeletal muscle.
-Intradermal type - Lesion present in the dermis (intradermal
fasciitis).
Early cases of Nodular fasciitis display zonation effect with maturation
from the centre (hypocellular or hyalinized) to the periphery (hypercellular
with inflammatory cell , blood vessels).
In between, the loose myxoid area is populated by non- pleomorphic
myofibroblasts loosely arranged with a tissue culture look .The backround
stroma shows variable myxoid change.
Myxoid Tumours of Soft Tissue
Extravasated red blood cells and lymphocytes (not plasma cells) are also
present.
Later lesions demonstrate a variety of storiform areas, interconnecting
bundles, myxoid areas or focal cystic areas. Hyalinization and keloidal
change may be noted in longstanding cases.
There are 1-2 normal mitotic figures per 5 / HPF (Note:
More than 1 mitosis / HPF and atypical forms raises the possibility of a
malignant tumour).
Immunohistochemistry
:
NF demonstrates focal smooth muscle and muscle specific actin and
calponin, but not usually desmin, h-caldesmon or CD34. CD68 may be
positive in some cases.
[Similar microscopic features are present in reactive fasciitis-like
lesions occuring
-In deep soft tissue location, eg- nerve, parotid sheath .
-In viscera , eg- i) postoperative spindle cell nodule-bladder, prostate, vagina.
ii) inflammatory fibromyxoid tumour-bladder
iii) proliferative funiculitis -spermatic cord
Differential diagnosis:
A. Benign tumours:
1.Benign fibrous histiocytoma-
Classical -Epidermal hyperplasia, peripheral collagen bundles, foamy macrophages and Touton giant cells .
Cellular variant- Fascicular spindle cell architecture.
2.Neurofibroma- Architecture is different, S100 protein is positive
3.Spindle cell lipoma - Fat, ropy collagen, absence of markers
4.Fibromatosis- More infiltrative growth pattern, slender spindle shaped
fibroblasts arranged in sweeping fascicles and separated by abundant
intercellular collagen.
B. Malignant tumours:
1. Leiomyosarcoma-
The cells in fasciitis are tapered and the nuclei are tapered rather than
blunt ended. Atypical mitotic figures are prominent.Immunohistochemistry
reveals h-caldesmon and desmin positivity.
2. Low grade myofibrosarcoma (myofibroblastic
sarcoma) shows focal nuclear
atypia,less inflammation, more uniformly cellular, reaches a larger size
and infiltrates muscle.
3. Inflammatory myofibroblastic tumour has
fasciitis-like,fascicular and fibrous areas and a marked plasma cell
infiltrate. Immunohistochemistry reveals that some cases are cytokeratin
and ALK-1 positive.
4. Myxoid malignant fibrous
histiocytoma is multinodular
,has vacuolated fibroblasts and shows nuclear pleomorphism, abnormal
mitosis, distinct vascular pattern and is usually actin negative (some are
CD34 positive).
5. Malignant peripheral nerve sheath
tumour has alternating
cellular and myxoid fascicles, is more uniform and has wavy buckled and
bullet shaped nuclei. Better differentiated case are at least focally
S100 protein positive and myoid markers are negative.
The following features rule
out malignant tumour:
1. Absence of atypia 2. Absence of atypical mitotic figures 3.Small
size 4.Short history 5.Superficial location in young adults.
Variants:
1. Ossifying fasciitis:
Nodular fasciitis like fibroblastic proliferations with metaplastic bone
formation.
2. Intravascular fasciitis:
Involve small or medium-sized veins or arteries. Histologically the
features are similar to nodular fasciitis, however there are greater
number of multinucleate giant cells and less prominent mucoid matrix.
3. Cranial fasciitis:
The lesion involves the soft tissue
of the scalp land is usually present in infants. Histologically this is
well circumscribed lesion showing NF like fibroblastic proliferation in a
prominent myxoid stroma. IMAGE LINKS1
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