Solitary Fibrous Tumor of the Vagina with Potentially Malignant Features: A Case Report and Review of the Literature
Asuman Nihan HABERAL REYHAN
Department of Pathology, Başkent University Faculty of Medicine, ANKARA, TURKEY
Keywords: Solitary fibrous tumor, Vagina, Hemangiopericytoma, Female genital neoplasms
Extrapleural solitary fibrous tumors are being increasingly reported. The retroperitoneum, deep soft tissues of the proximal extremities, abdominal
cavity, trunk, head and neck are among the most common extraserosal locations reported. A recurrent solitary fibrous tumor involving the
vagina of a 25-year-old woman is reported. Microscopically, the tumor was hypercellular and composed of mitotically active spindle cells.
Immunohistochemically, the tumor cells were positive for vimentin, CD34, and bcl-2. Four cases of solitary fibrous tumors involving the vagina
have been reported previously. To the best of our knowledge, this is the first case with clinical and histological features suggestive of a malignant
The solitary fibrous tumor (SFT) is an uncommon
spindle cell neoplasm of mesenchymal lineage that was
first recognized as a distinctive pleural lesion in 1931.
Extrapleural SFTs have been increasingly reported.
The retroperitoneum, deep soft tissues of the proximal
extremities, abdominal cavity, trunk, head and neck are the
most common extraserosal locations reported1,2
To the best of our knowledge, there have been only 4
previous case reports of a primary vaginal SFT in the
English literature3-6. In this article we describe a fifth
case that recurred 4 years after the first excision. We believe
that this is the first report describing an SFT of the vagina
displaying clinical and histological features suggestive of a
The patient was 21 years old when she felt a mass at
the vagina around the hymen that was resected and
histologically examined at another institution. Four years
after the first excision, when she was 25 years old, she felt a
mass at the same site again. A pelvic examination revealed
a raised, firm, recurrent nodule measuring approximately
1.5 cm at the vagina around the hymen, and the mass was
surgically reexcised. The recurrent tumor submitted for
histopathological examination consisted of an irregularly
shaped piece of tan, rubbery, soft tissue measuring 1.5x1.3x 0.8 cm. The resection margins were carefully painted, and
the specimen was submitted totally.
Microscopically, the lesion was a well-circumscribed nodule
that was separated from the intact vaginal mucosa by a narrow
fibrous zone (Figure 1). The tumor was hypercellular and
consisted of spindle to ovoid cells with prominent nucleoli
(Figure 2). No fascicles or a storiform pattern was seen. Areas
of necrosis were not detected but there were up to 4 mitotic
figures per each high power field (approximately 14 mitotic
figures per 10 high power fields) (Figure 3). The neoplastic
cells were diffusely positive for vimentin (Ab-2, NeoMarkers,
Fremont, USA), CD34 (Ab-1, NeoMarkers, Fremont, USA),
and Bcl-2 protein (Ab-1, NeoMarkers, Fremont, USA) (Figure 4A,B). They were only focally positive for pancytokeratin
(PAN-CK Cocktail, Ab-2, NeoMarkers, Fremont, USA)
and CD10 (Ab-2, NeoMarkers, Fremont, USA) and were
negative for CD99 (Ab-1, NeoMarkers, Fremont, USA),
SMA (Ab-1, NeoMarkers, Fremont, USA), S100 (DAKO,
Glostrup Denmark), EMA (Ab-2, NeoMarkers, Fremont,
USA), and HMB-45 (Melanoma (gp100)Ab-3, NeoMarkers,
Fremont, USA). The surgical resection margins were clear.
Ki-67 (Clone SP6, NeoMarkers, Fremont, USA) proliferation
index of the tumor was 8%.
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|Figure 1: Well-circumscribed nodule separated from the intact
mucosa by a narrow fibrous zone (H&E; x40).
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|Figure 2: Hypercellular tumor that consisted of spindle to ovoid
cells with prominent nucleoli (H&E; x200).
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|Figure 3: Two mitotic figures are seen in a high power field
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|Figure 4: The neoplastic cells were diffusely positive for CD34
(A), and bcl-2 protein (B) (Immunoperoxidase x100).
A piece of tumor tissue was retrieved from the paraffin
block for electron microscopic study. This was fixed first in
2.5% gluteraldehyde for 2-3 hours; and then in 1% osmium
tetraoxide (OsO4) and dehydrated in a series of graded alcohols (25%, 50%, 75%, 95%, and absolute alcohol).
After passing through propylene oxide, the specimens
were embedded in araldyte CY 212, DDSA (2-dodecenyl
succinic anhydride), BDMA (benzyldimethyl amine) and
dibutylpytalate. Semithin sections were cut and stained
with toluidine blue and examined with a light microscope.
Ultrathin sections were stained with uranyl acetate and
lead citrate and examined with LEO 906E EM transmission
electron microscope. Ultrastructuraly, the tumor was
hypercellular without a distinguishing organelle suggestive
of a specialized line of differentiation (Figure 5). Specifically,
Weibel-Palade bodies, prominent pinocytic vesicles or
multiple cytoplasmic processes that might suggest certain
other lines of differentiation were not seen.
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|Figure 5: Ultrastructure of a tumor cell. No distinguishing
organelle suggestive of a specialized line of differentiation is
present (Electron microscopy x6000 magnification).
After the diagnosis of SFT with features suggestive of a
malignant behavior, the patient was re-evaluated clinically
and imaging studies were done to detect other recurrent
or metastatic foci. These included abdominal and thoracal
computerized tomography, pelvic ultrasonography, and a
chest X-ray. Neither a recurrent nor a metastatic focus was detected. The patient is alive and free of disease 7,5 years
after the second excision.
Solitary fibrous tumor (SFT) is a spindle-cell neoplasm
most often presenting as a pleural-based tumor but it
is increasingly recognized in other locations. To our
knowledge, there have been only 4 previous case reports of
a primary vaginal SFT in the English literature and some
features of these were summarized in Table I
SFTs are often asymptomatic and found incidentally in
the course of evaluation for another medical problem.
Histologic features overlap to a great extent with other
tumors consisting mostly of spindle to ovoid cells and
immunohistochemistry plays a significant role in diagnosis.
The differential diagnosis of SFT includes neurofibroma,
leiomyoma, spindle cell epithelioma, and myofibroblastoma
of the vagina. Neurofibroma has wavy bundles of slender
spindle cells with palisaded arrangement, has small
nuclei, and is positive for S1005. Leiomyoma consists
of interlacing fascicles of spindle cells with elongated
nuclei; and is positive for desmin, actin, and caldesmon5. Spindle cell epithelioma can be purely mesenchymal
and histologically very similar to SFT and besides is also
positive for CD34, bcl-2, and CD99 as is SFT. However,
spindle cell epithelioma is strongly positive for epithelial
and smooth muscle markers, whereas SFT is negative for
those markers6. Myofibroblastoma may mimic SFT, but myofibroblastoma of the lower genital tract is positive for
desmin, SMA, and estrogen-progesterone receptors6.
Typically, a SFT is positive for vimentin and CD34. Other
antigens frequently expressed by lesional cells include bcl-
2 and CD99. Strong desmin, S-100 and CD68 expressions
may help exclude a lesion from SFT category. Our lesion’s
immunohistochemical profile is consistent with SFT.
The criteria for predicting malignant clinical behavior
(local recurrence or distant metastases) include the
following: large tumor size (more than 5 cm), infiltrative
margins, high cellularity, nuclear pleomorphism, areas
of tissue necrosis and increased mitotic index (more
than 4 mitosis in 10 HPF) and these factors should be
included in the pathology report7-9. In our case, the
high cellularity and the increased mitotic index about 4
mitotic figures per each high power field were the features
suggestive of a malignant behavior in the recurrent tumor.
In a recent article published by Demicco et al., the authors
clinicopathologically analyzed 110 cases of solitary fibrous
tumor (primary soft tissue: 79 cases, and pleural solitary
fibrous tumors: 31 cases), and suggested a risk stratification
model based on age, size, and mitotic index10. According
to this model a 3–tiered model stratifying the patients by
overall risk of metastasis (low, moderate, or high) was
developed. Scores were assigned for age (<55: score 0 vs.
≥55: score 1), tumor size (<5: score 0, 5 to <10: score 1, 10 to
<15: score 2, or ≥15 cm: score 3), and mitotic figures/10 high
power fields (0: score 0, 1–3: score 1, or ≥4: score 2), and
total scores calculated to determine the risk of aggressive
disease. The overall risk of metastasis is predicted to be low
if the total score is 0-2, moderate for 3-4 and high for 5-610. According to these criteria our case had a score 2 and
the overall risk of metastasis was predicted to be low.
We could not detect any distinguishing organelle suggestive
of a specialized line of differentiation by transmission
electron microscopy as was reported previously by Ide
et al in some of their cases11. They suggest that SFT
probably originates from perivascular stem cells which
can differentiate along 3 evolutional lines as endothelial,
pericytic, and fibroblastic by following a pathway that
occurs in normal angiogenesis11.
The behavior of SFT is unpredictable. The relationship
between morphology and outcome is not always clear cut.
Some “malignant” tumors behave in a benign fashion while
some morphologically “benign” lesions behave aggressively.
In addition to the presence of histological criteria of
malignancy, the absence of sclerotic-hypocellular areas and
a tumor size of more than 10 cm suggest a poor outcome
and these cases may deserve close follow-up9. The
tumor in our case recurred 4 years after the first excision.
However, distant metastases were not detected. The patient
is alive and well today, 7.5 years after her second operation.
In conclusion, we have described a case of primary SFT
of vagina with malignant histological features. We believe
this is the first case displaying these features as reported
in the literature. The typical histological appearance of
the tumor, the electron microscopic characteristics and
the confirmatory immunohistochemical panel aided
in the diagnosis. Despite the fact that SFT is rare in the
female genital tract, it should always be considered in
the differential diagnosis of lesions showing fibroblastic,
muscular, neural, and myofibroblastic differentiation.
Most SFTs are said to behave in a benign fashion after
complete excision. However, patients should be followed
up closely due to the unpredictable clinical behavior. This is
especially important for tumors that display unusual gross
or histological features like those described in our case.
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