DISCUSSION:
AFH was initially described by Enzinger1 in 1979 as
malignant angiomatoid fibrous histiocytoma. They constitute around 0.3%
of all soft tissue tumors.2-5. However, the data may
be understated because of the overlapping histopathological
findings.5 But, The World Health Organization (WHO) in
2013 classification placed it in the category of “intermediate tumors
of uncertain differentiation” because of its better
prognosis2,4-13 .Although AFH can occur at any age but
most patients present in the first three decades of life .In our case,
the patient was in her forties. Although patients with AFH typically
present with a painless subcutaneous soft tissue
lump5,10 , Costa and Weiss3 reported
that 18% of tumors invaded deep structures such as skeletal muscle. In
our case, it was a painless swelling in the popliteal fossa region.
Intraoperatively it was intraarticular in location and stump was found
to be attached to the underlying bone. It most commonly arises in sites
of normal lymphoid tissue such as the antecubital fossa, axilla,
inguinal and supraclavicular regions 5,8,13.The
majority of cases occur in the extremities, although cases have been
reported in the head and neck region (10%) and trunk1,5,6,13. The cumulative findings of a meta-analysis
of multiple studies demonstrate that the majority of patients (73.2%)
are disease free after local excision and a minority (23.2%) develop
recurrent disease and 8.7% metastasise within 24 months of surgery3. Metastasis occurs predominantly to regional lymph
nodes but exceptionally to the lungs, liver, or
brain.13
Making a pre-operative diagnosis of AFH is challenging with no distinct
clinical or imaging findings to lead to diagnosis. There is a vast
variability of the differential diagnoses which includes: Aneurysmal
bone cysts, schwannoma, synovial sarcomas, aneurysmal fibrous
histiocytomas, follicular dendritic metastatic tumor of lymph nodes
.11,13 The presence of systemic symptoms, such as
weight loss, malaise, fever, and anemia , which occur in some patients,
can aid diagnosis5,6,10,11 The cause of these
constitutional symptoms are thought to be due to the tumoral cytokine
production5. However, in the current case, the patient
experienced no systemic symptoms.
The imaging modalities are not diagnostic but aid in the management. The
Computed tomography may show a heterogeneous mass and possibly hint at
cystic and enhancing components. MRI is superior to CT scan for the
diagnosis and explaining the relationship with the surrounding
structures5 .Although the MRI features of AFH
described in the literature may aid diagnosis , none of them are
considered to be significant11 .MR has been
traditionally used for postoperative follow-up. MRI was not done in our
case due to non-availability in our institute and we proceeded with an
excisional biopsy after the USG report.
Histopathological features of AFH have been well described2,11.This includes the following features:(i)
multinodular growth of myoid spindle or histiocytoid cells with a
distinctive syncytial appearance, (ii) pseudoangiomatous spaces filled
with blood and surrounded by tumor cells, (iii) a thick fibrous
pseudocapsule with prominent hemosiderin deposition, and (iv)
peritumoral lymphoplasmacytic cuffing with occasional germinal centre
formation. These features were consistent to our case. AFH lacks a
specific immunoprofile, so that immunohistochemistry is supportive
rather than diagnostic. Immunohistochemistry variably demonstrates
positivity for desmin, CD68 and CD99 5,7,9-12 .Lastly,
cytogenetic analysis has recently added to the diagnosis of AFH, with
the EWSR1-CREB1 fusion gene present in the majority of
AFH5,8-12
The prognosis of AFH is generally considered to be
favorable2,9-12 but because of its chances of local
recurrence ,soft tissue sarcomas should be operated by a specialised
surgeon and special consideration should be taken not to miss these
tumors preoperatively . There should be wide surgical excision with
clear margins. Extended resection of AFH is recommended because the
tumor is considered intermediate and not purely benign as it requires
continued clinic radiological surveillance 5 .
There were some limitations in the current study. We did not perform
immunohistochemistry for desmin and did not examine fusion genes, which
are often useful for differential diagnosis. However, a diagnosis of AFH
could be made in specimen Biopsy. Given the intermediate malignant
potential of this lesion, the patient will require continued clinical
and radiographic surveillance.