Solitary Fibrous Tumor of the Vagina with Potentially Malignant Features : A Case Report and Review of the Literature

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 behavior.


INTRODUCTION
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 reported (1,2).
To the best of our knowledge, there have been only 4 previous case reports of a primary vaginal SFT in the English literature (3)(4)(5)(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 malignant behavior.

CASE REPORT
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 1.5x1.3x0.8 cm.The resection margins were carefully painted, and the specimen was submitted totally.
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 (OsO 4 ) and dehydrated in a series of graded     A B 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.

Solitary Fibrous Tumor of the Vagina with Potentially Malignant Features: A Case Report and Review of the
detected.The patient is alive and free of disease 7,5 years after the second excision.

DISCUSSION
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 S100 (5).Leiomyoma consists of interlacing fascicles of spindle cells with elongated nuclei; and is positive for desmin, actin, and caldesmon (5).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 markers (6).Myofibroblastoma may mimic SFT, but 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   (10).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 5-6 (10).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 cases (11).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 angiogenesis (11).
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-up (9).The tumor in our case recurred 4 years after the first excision.

Figure 3 :
Figure 3: Two mitotic figures are seen in a high power field (H&E; x400).

Figure 5 :
Figure 5: Ultrastructure of a tumor cell.No distinguishing organelle suggestive of a specialized line of differentiation is present (Electron microscopy x6000 magnification).

Table I :
A review of the vaginal SFT cases in the literature