Solitary fibrous tumour of the female genital tract: a clinicopathological analysis of 25 cases

Sex Cord-Stromal Tumors of the Ovary: An Update and Review. Part I - Pure Ovarian Stromal Tumors

In two separate reviews, we review the time-honored but still frequently challenging features of ovarian sex cord-stromal tumors, and also emphasize new developments including unusual morphologic appearances that, despite the relative rarity of many of the tumors, result in a disproportionate number of differential diagnostic problems, variant immunohistochemical profiles, and specific molecular and syndromic associations. These neoplasms are also of historical interest as current knowledge is still based in significant part on the contributions of 2 giants of gynecologic pathology, Dr Robert Meyer and Dr Robert E. Scully. In part I, we present the major clinical, pathologic, and genomic features of the pure ovarian stromal tumors including comments on differential diagnosis and briefly note significant historical contributions. In part II we will discuss pure sex cord and sex cord-stromal tumors.

Poorly differentiated biphasic synovial sarcoma of the vulva, displaying SS18::SSX1 fusion and weak to absent (mosaic) INI1/SMARCB1 immunostaining: A rare case with literature review

ABSTRACT

Synovial sarcoma (SS) is rarely documented in the female genital tract, especially confirmed by molecular testing for SYT::SSX translocation and TLE1 immunostaining. A 62-year-old lady presented with a progressively increasing lump and pain over her right groin, for 6-month duration. Radiologically, a well-defined, solid-cystic mass was seen involving the right labia with necrotic areas, sparing the underlying muscles and the overlying skin. She underwent a biopsy followed by a surgical excision. Histopathologic examination revealed a spindle cell sarcoma, including tumor cells exhibiting a prominent hemangiopericytomatous pattern. There were focal areas of epithelial differentiation (pseudoglandular) along with areas of round cell morphology and increased mitoses (poor differentiation) in the resected specimen. Immunohistochemically, the tumor cells were diffusely positive for TLE1, patchily positive for pan keratin (AE1/AE3) and EMA, the latter more in the areas of epithelial differentiation, while negative for CD34, SMA, desmin, S100P, and SOX10. INI1/SMARCB1 showed a characteristic weak to absent (mosaic) staining pattern. Furthermore, the tumor displayed SS18::SSX 1 fusion by RT-PCR. This constitutes one of the few reported cases of vulvar SS, confirmed by molecular testing and the first documented vulvar SS showing a mosaic pattern of INI1/SMARCB1 immunostaining. A review of the literature and diagnostic implications are presented herewith.

Diagnostics and Treatment of Extrameningeal Solitary Fibrous Tumors

Solitary fibrous tumors (SFT) are rare mesenchymal neoplasms that account for less than 2% of all soft tissue masses. In the latest WHO 2020 Classification of Soft Tissue Tumors, extrameningeal SFT was listed as intermediate (rarely metastasizing) or malignant neoplasms. Due to the lack of characteristic clinical features, their diagnosis and treatment remain challenging. The pathogenesis of SFT is often associated with the presence of fusions of the NAB2-STAT6 gene on the 12q13 chromosome. Cytoplasmic CD34 positive staining is considerably characteristic for most SFTs; less frequently, factor XII, vimentin, bcl-2, and CD99 are present. A key factor in the diagnosis is the prevalent nuclear location of STAT6 expression. Radical resection is the mainstay of localized SFTs. In the case of unresectable disease, only radiotherapy or radio-chemotherapy may significantly ensure long-term local control of primary and metastatic lesions. To date, no practical guidelines have been published for the treatment of advanced or metastatic disease. Classical anthracycline-based chemotherapy is applicable. The latest studies suggest that antiangiogenic therapies should be considered after first-line treatment. Other drugs, such as imatinib, figitumumab, axitinib, and eribulin, are also being tested. Definitive radiotherapy appears to be a promising therapeutic modality. Since standards for the treatment of advanced and metastatic diseases are not available, further investigation of novel agents is necessary.

Diagnosis and management of a pelvic solitary fibrous tumor in a postmenopausal woman - a case report

Background

Solitary fibrous tumors, previously known as hemangiopericytomas, originate from mesenchymal tissue and can occur at many body sites, such as the thorax, head and neck, retroperitoneal space and abdomen. These tumors are generally rare and pelvic location is extremely uncommon. Consequently, pelvic solitary tumors could be mistaken for ovarian cancer in menopausal women. This report presents a case of pelvic solitary tumor to highlight the importance of considering this diagnosis in a postmenopausal woman presenting with a solid pelvic mass, normal tumor markers and no ascites.

Case

A 54-year-old woman presented with amenorrhea, abdominal pain, constipation, nausea, vomiting, and frequency of urination. On examination she had a pelvic mass of approximately 20-24 weeks in size. Ultrasound and computed tomography imaging showed a well-defined, round, centrally hypodense, irregular thick and peripheral, enhancing solid mass originating from the left ovary. Carcinoembryonic antigen, carbohydrate antigen-125, and carcinoembryonic antigen 19-9 were all normal. Intraoperatively the tumor was attached to the peritoneum and mesentery. Part of the large bowel, including the sigmoid colon, were attached to it. The exact origin of the tumor could not be ascertained during surgery. The tumor was successfully excised, and specimen sent for histology and immunochemistry analysis. The definitive diagnosis was confirmed with immunochemistry. The patient had an uneventful postsurgical course and was discharged on day 4 after surgery for routine gynecological follow-up.

Conclusion

Solitary fibrous tumor is very rare; however, the diagnosis should be considered in a postmenopausal woman with solid pelvic mass, normal tumor markers and no ascites.

Large Solitary Fibrous Tumor (SFT) of the penis- a case report and review of literature

BACKGROUND

Solitary fibrous tumors (SFTs) are very rare spindle cell neoplasms of mesenchymal origin with largely benign course of disease. Genital SFT's can be managed providing excellent functional and psychological outcomes by timely intervention.

CASE PRESENTATION

We report the largest and possibly the second only reported case of penile SFT in a 34 year male presenting with a gradually increasing perineal mass with clinically normal appearing phallus. MRI revealed a 9.8 × 3.2 cm soft tissue mass arising from left corpora cavernosae, the mass was excised en-bloc via a perineal approach under spinal anaesthesia. Histopathology revealed spindle cell tumor embedded in myxohyaline stroma along with hyalinized vascular channels demonstrating IHC positivity for CD34 and STAT6. The patient is disease free post 2 years of resection with no sexual or urinary dysfunctions.

CONCLUSION

Genital SFTs, although rare, should be considered in the differential diagnosis of well-circumscribed, painless, slow growing solid masses and histopathologists must be vigilant of its malignant characteristics.

Sclerosis in Sex Cord-Stromal Tumors Other Than the Sclerosing Stromal Tumor: A Report of 70 Cases

Sclerosis is well-known in sclerosing stromal tumors (SSTs), as its name indicates, but has not been evaluated in other ovarian sex cord-stromal tumors (SCSTs). Its presence in other SCSTs has sporadically caused diagnostic problems in cases we have seen, and this prompted us to review SCSTs with appreciable sclerosis; tumors containing at least 20% sclerosis were included. Seventy cases were identified: 20 thecomas, 20 juvenile granulosa cell tumors (JGCTs), 8 adult granulosa cell tumors (AGCTs), 5 sex cord tumors with annular tubules, 6 retiform Sertoli-Leydig cell tumors (SLCTs; all of the intermediate differentiation), 4 nonretiform SLCTs (3 well-differentiated, 1 of intermediate differentiation with heterologous elements), 4 Sertoli cell tumors, and 3 microcystic stromal tumors (MSTs). Paucicellular sclerotic zones comprised 20% to 95% of the tumors and when conspicuous often obscured diagnostic features. Thirty-one tumors (10 thecomas, 19 JGCTs, 1 AGCT, and 1 MST) showed sclerotic zones focally enveloping nodules of tumor cells, imparting a pseudolobular appearance, and sclerosis often occurred within lobules as well. Ten of these (5 thecomas and 5 JGCTs) also had prominent staghorn blood vessels, generating a low-power appearance focally similar to SST. In 17 tumors, the sclerosis resulted in "compression" of the tumor cells into cords and/or solid tubules. Correct diagnosis in these cases is dependent on careful examination of the cellular zones of the neoplasms, but awareness of the extent of sclerosis that may be seen in diverse SCSTs may be crucial in suggesting the correct diagnosis particularly when the material is limited as in the intraoperative setting. Our findings highlight for the first time the occurrence and character of sclerosis in sex cord tumors other than SSTs and fibromas. Sclerosis is seen in descending proportion of the tumor types as follows: retiform SLCTs, thecomas, MSTs, JGCTs, sex cord tumors with annular tubules, Sertoli cell tumors, AGCTs, and nonretiform SLCTs. Its character can vary somewhat, having particular features in the sex cord tumor with annular tubules (hyaline material within tubules often coalescing and extending beyond the nests to form confluent aggregates) and retiform SLCTs (common in papillary cores).

Update on Ovarian Sex Cord-Stromal Tumors

This article focuses on the recent advances in ovarian sex cord-stromal tumors, predominantly in the setting of their molecular underpinnings. The integration of genetic information with morphologic and immunohistochemical findings in this rare subset of tumors is of clinical significance from refining the diagnostic and prognostic stratifications to genetic counseling.

ALK Immunoexpression is Specific for Inflammatory Myofibroblastic Tumor Among Vulvovaginal Mesenchymal Neoplasms

Gynecologic tract origin of inflammatory myofibroblastic tumor (IMT), a receptor tyrosine kinase fusion driven tumor with malignant potential, is uncommon and mostly involves the uterine corpus where misclassification as a smooth muscle tumor may occur due to overlapping morphologic features. With rare exception, uterine IMT involves ALK rearrangements and exhibits ALK immunoexpression. Molecularly confirmed vulvovaginal IMT has not been reported, but several low-grade mesenchymal tumors in this region exhibit myxoid stroma and/or inflammatory infiltrates that may resemble IMT. The aims of this study were to define the diagnostic specificity of ALK immunoexpression for IMT among a broad spectrum (107 cases) of vulvovaginal mesenchymal tumors in the differential diagnosis of IMT and to report the clinicopathologic features of vulvovaginal IMT identified in our archives or via retrospective ALK staining of otherwise classified vulvovaginal tumors. Review of archives from 5 different centers revealed a single case of vulvar IMT in a 62-yr-old woman. The 2.5 cm well-circumscribed tumor exhibited the typical microscopic features of IMT, namely a loose fascicular distribution of bland spindle cells within a myxoid stroma, accompanied by an infiltrate of plasma cells, lymphocytes, and eosinophils. The tumor cells exhibited expression for smooth muscle actin, desmin, h-caldesmon, and ALK. Break-apart fluorescence in situ hybridization confirmed the presence of ALK rearrangement. The patient did not receive any treatment and is alive without disease 32 mo later. No evidence of ALK expression was detected in any of the other 107 vulvovaginal tumors, which included 14 aggressive angiomyxomas, 2 superficial angiomyxomas, 12 angiomyofibroblastomas, 8 cellular angiofibromas, 15 smooth muscle neoplasms, 10 peripheral nerve sheath tumors, 20 fibroepithelial polyps, and a variety of other low grade mesenchymal tumors. Although vulvovaginal ALK- rearranged IMT is exceedingly rare, the behavior remains to be fully understood. ALK immunohistochemistry, which appears specific for IMT in this anatomic site, is advised in the evaluation of vulvovaginal mesenchymal tumors exhibiting myxoid stroma and/or an inflammatory infiltrate.

NTRK -Rearranged Uterine Sarcomas: Clinicopathologic Features of 15 Cases, Literature Review, and Risk Stratification

NTRK -rearranged uterine sarcomas are rare spindle cell neoplasms that typically arise in the uterine cervix of young women. Some tumors recur or metastasize, but features which predict behavior have not been identified to date. Distinguishing these tumors from morphologic mimics is significant because patients with advanced stage disease may be treated with TRK inhibitors. Herein, we present 15 cases of NTRK- rearranged uterine sarcomas, the largest series to date. Median patient age was 35 years (range: 16 to 61). The majority arose in the uterine cervix (n=14) and all but 2 were organ-confined at diagnosis. Tumors were composed of an infiltrative, fascicular proliferation of spindle cells and most showed mild-to-moderate cytologic atypia. All were pan-TRK positive by immunohistochemistry (13/13); S100 (11/13) and CD34 (6/10) were usually positive. RNA or DNA sequencing found NTRK1 (10/13) and NTRK3 (3/13) fusions with partners TPR , TPM3 , EML4 , TFG , SPECC1L , C16orf72 , and IRF2BP2 . Unusual morphology was seen in 2 tumors which were originally diagnosed as unclassifiable uterine sarcomas, 1 of which also harbored TP53 mutations. Follow up was available for 9 patients, of whom 3 died of disease. By incorporating outcome data of previously reported tumors, adverse prognostic features were identified, including a mitotic index ≥8 per 10 high-power fields, lymphovascular invasion, necrosis, and NTRK3 fusion. Patients with tumors which lacked any of these 4 features had an excellent prognosis. This study expands the morphologic spectrum of NTRK -rearranged uterine sarcomas and identifies features which can be used for risk stratification.

Clinical characteristics and prognosis of orbital solitary fibrous tumor in patients from a Chinese tertiary eye hospital

BACKGROUND

Solitary fibrous tumor (SFT) is predominant within the pleura but very rare in the orbit, which is why the diagnosis of orbital SFT poses challenges in clinical practice. Accordingly, an integrated approach that incorporates specific clinical features, histological, histopathological, and immunohistochemical (IHC) examinations, and molecular analyses is warranted.

AIM

To retrospectively explore the clinical and imaging characteristics, treatment, outcomes of a series of patients with orbital SFT.

METHODS

We conducted a retrospective review of a series of patients diagnosed with a histopathologic orbital SFT treated at a single institution. All data on demographics, clinical characteristics, imaging, treatment, postoperative histopathological and IHC examinations, and prognosis were collected.

RESULTS

In total, 13 patients were enrolled, 7 (53.8%) of whom had the tumor located in the superomedial quadrant of the orbit. Computed tomography revealed a solitary ovoid lesion in 10 (76.9%) patients and irregular lesion in 3 (23.1%) patients. Magnetic resonance imaging results were as follows: On T1 weighted images, 3 (23.1%) patients had hypointense mixed signals, whereas 10 (76.9%) patients showed isointense mixed signals; on T2 weighted images (T2WI), 3 (23.1%), 4 (30.8%), and 6 (46.2%) patients exhibited hypointense mixed, isointense mixed, and hyperintense signals, respectively. Notably, 12 (92.3%) patients showed significant enhancement, whereas there were patchy slightly enhanced areas in the tumor. All patients were treated by surgery. IHC analysis demonstrated that the tumor cells were immunoreactive for CD34, CD99, STAT-6, and vimentin in all patients. The lesions showed Ki-67 positivity < 5% in 1 (7.7) patient, 5%-10% in 10 (76.9%), and > 10% in 2 (15.4%). Two (15.4%) patients exhibited tumor recurrence.

CONCLUSION

The clinical manifestations and radiologic characteristics of orbital SFT are diverse and not specific. Accurate diagnosis and treatment require detailed radiological and histopathological/ IHC evaluation.

Update on Mesenchymal Lesions of the Lower Female Genital Tract

This article provides an update of the recent developments in mesenchymal tumors of lower genital tract. We focus on the characterization of recurrent molecular events in certain genital stromal tumors, for instance angiomyofibroblastomas and superficial myofibroblastomas. Moreover, fusions involving Tyrosine-kinases receptors (NTRK, FRFR1, RET, COL1A1-PDGFB) have been demonstrated in an emerging group of mesenchymal tumors characterized by a fibrosarcoma-like morphology and a predilection for uterine cervix of premenopausal women. We also cover the topic of smooth muscle tumors of the lower genital tract, which can be now classified using the same diagnostic criteria than their uterine counterpart..

Update on Ovarian Sex Cord-Stromal Tumors

This article focuses on the recent advances in ovarian sex cord-stromal tumors, predominantly in the setting of their molecular underpinnings. The integration of genetic information with morphologic and immunohistochemical findings in this rare subset of tumors is of clinical significance from refining the diagnostic and prognostic stratifications to genetic counseling.

Nonsquamous Lesions of the Vulvar Skin and Subcutaneous Tissue: A Review (Part 2)

OBJECTIVE

The aim of this second article was to complete part 1 review of nonsquamous lesions of the vulvar skin and subcutaneous tissue (Journal of Lower Genital Tract Disease, 2021), clinically and pathologically, based on the fifth edition of the World Health Organization tumor classification.

MATERIALS AND METHODS

A database search of PubMed and Google Scholar was performed between 1970 and 2021, using the search terms "vulva," "lower genital tract," and "non-squamous lesions." The search was limited to "human gynecological pathology." Full article texts were reviewed, and reference lists were screened for additional articles. We excluded abstracts and articles written in the non-English language.

RESULTS

An initial list of 400 articles was identified. Thirty-seven articles discussed clinicopathological features of nonsquamous lesions of the vulvar skin and subcutaneous tissue.

CONCLUSIONS

Clinicopathological features of nonsquamous lesions of the vulvar skin and subcutaneous tissue as categorized by the updated World Health Organization classification are presented.

Solitary Fibrous Tumors of the Female Genital Tract: A Study of 27 Cases Emphasizing Nonvulvar Locations, Variant Histology, and Prognostic Factors

We report 27 solitary fibrous tumors of the female genital tract emphasizing nonvulvar locations, variant histology, and prognostic factors. The patients ranged from 25 to 78 years (most were over 40), and tumors occurred in the vulva (7), vagina (2), cervix (2), corpus (6), fallopian tube/paratubal soft tissue (5), and ovary (5). They ranged from 1.5 to 39 (mean=10.5) cm and were typically solid, but 4 were predominantly cystic. All had a haphazard arrangement of spindled to ovoid cells, with most demonstrating alternating cellular and hypocellular areas and prominent vessels, but 13 lacked hypocellular areas, and 7 had focal diffuse growth with inconspicuous vasculature. Other patterns included corded (8), fascicular (5), trabecular (1), and nested (1). Microcysts (6), myxoid background (8), hyalinization (8), lipomatous differentiation (2), and multinucleated cells (6) were also present, and 10 tumors had necrosis. Vasculature included thin-walled branching "staghorn" (27), thick-walled (7), and hyalinized vessels (5) or dilated anastomosing vascular channels (3). Nuclear atypia ranged from mild (19), moderate (7), to severe (1), and mitoses from 0 to 24/10 HPF (mean=4). STAT6 was positive in all 25 tumors tested. One tumor showed dedifferentiation; the remainder were classified as benign (19) or malignant (7) based on mitotic rate (univariate stratification model) and as low risk (14), intermediate risk (8), or high risk (4) based on the Demicco multivariate risk stratification score. Follow-up (median=23 mo) was available for 16 patients. Six tumors recurred (2 intermediate risk, 3 high risk, and the dedifferentiated tumor), 5 in the abdomen; the dedifferentiated tumor metastasized to the lung. Multivariate risk stratification was superior to univariate classification, as 5 "benign" tumors were reclassified as intermediate risk using the multivariate model; of these, 2 recurred, and 1 patient died of disease. Upper female genital tract tumors occurred in older patients, were larger, and more frequently classified as high risk compared with those of the lower tract. A trend toward increased cellularity was also seen in the upper tract tumors. Only size (P=0.04), necrosis (P=0.04), and Demicco score (P=0.01) independently correlated with recurrence. Female genital tract solitary fibrous tumors demonstrate a wide range of variant morphologies and occur in diverse sites in addition to the vulva. Tumors were often misdiagnosed as other neoplasms; thus, awareness of solitary fibrous tumors occurring at these sites is crucial in prompting staining for STAT6 to establish this diagnosis. The Demicco risk stratification system effectively predicts behavior.

Solitary Fibrous Tumors Arising from Bilateral Ovaries: A Case Report and Review of the literature

BACKGROUND

A solitary fibrous tumor (SFT) is a distinct mesenchymal neoplasm. It was originally described as a tumor localized to the pleura but was later reported in several other anatomic sites and exhibited a wide spectrum of histological features. Owing to its rarity, the diagnosis of extrapleural SFT is challenging and requires an integrated approach comprising specific clinical, imaging, histological, and immunohistochemical findings.

CASE PRESENTATION

Herein, we report the imaging findings of a rare case of SFT arising from bilateral ovaries confirmed by surgical excision and histological examination. No adjuvant radiotherapy or chemotherapy was given to the patient, and she was disease-free with no evidence of recurrence or metastasis at the 96-month postoperative follow-up. Although it mostly follows a favorable course, SFT is notoriously difficult for prognostication because of its propensity for late relapse or even metastases in 10-39% of cases.

CONCLUSION

Close follow-up is recommended because of the limited information on its long-term behavior.

Intraoperative Frozen Section Biopsy of Uterine Smooth Muscle Tumors: A Clinicopathologic Analysis of 112 Cases With Emphasis on Potential Diagnostic Pitfalls

Frozen sections of uterine smooth muscle tumors are infrequently required, and related diagnostic difficulties are seldom discussed. We analyzed the clinicopathologic features of 112 frozen sections of uterine smooth muscle tumors and determined the accuracy, reasons for deferrals, and causes of interpretational errors. Most patients (median age, 45 y) presented with pelvic mass symptoms (53%). The main reasons for a frozen section examination were an abnormal gross appearance including loss of the usual whorled pattern of leiomyoma (36 cases, 32.1%), and intraoperative discovery of an abnormal growth pattern and extrauterine extension of a uterine tumor (28 cases, 25%). There were 9 leiomyosarcomas and 103 leiomyomas, including 18 benign histologic variants. An accurate diagnosis of malignancy was achieved in all leiomyosarcomas, with the exception of a myxoid leiomyosarcoma. In 99 cases (88%), the frozen section diagnosis concurred with the permanent section diagnosis (false positives, 0.9%; false negatives, 0%). Misinterpretation of stromal hyalinization as tumor cell necrosis in a leiomyoma with amianthoid-like fibers was a major discrepancy. Two minor discrepancies did not lead to a change in management. The diagnosis was deferred in 10 cases (8.9%) because of stromal alterations, unusual cellular morphology, uncertain type of necrosis, and abnormal growth patterns. Thus, although various stromal and cellular alterations can cause diagnostic uncertainty, leading to deferrals, frozen section diagnosis of uterine smooth muscle tumors has a high accuracy rate. While a definitive frozen section diagnosis of malignancy may be made when there is unequivocal atypia, indisputable mitotic figures, and tumor cell necrosis, it is important to remember that nonmyogenic mesenchymal tumors may also mimic uterine smooth muscle tumors. In a frozen section setting, it would be sufficient to issue a diagnosis of "malignant mesenchymal tumor." For tumors that do not meet the criteria for malignancy, issuing a frozen section diagnosis of "atypical mesenchymal tumor and defer the histologic subtyping to the permanent sections" is appropriate.

Sclerosing stromal tumour: a clinicopathological study of 100 cases of a distinctive benign ovarian stromal tumour typically occurring in the young

AIMS

Since the sclerosing stromal tumour (SST) of the ovary was first described in 1973, few studies have expanded upon its histological features or overlap with other tumours. We thus investigate these aspects based on our experience with 100 cases.

METHODS AND RESULTS

The patients, 14 of whom were pregnant, ranged from 12 to 63 years (median = 26 years). Ten patients had hormonal manifestations (seven oestrogenic, three androgenic). Bilateral ovarian involvement was present in two cases. Size ranged from 1 to 23 cm (mean = 8.4 cm). Most tumours were solid and white with focal yellow areas; oedema with cystic degeneration (seen in 25 cases) resulted in eight being predominantly cystic. On microscopic examination, alternating cellular and paucicellular areas (pseudolobulation) were prominent in 94 cases but seen to a limited degree in the remaining neoplasms. Admixed spindled and luteinised cells were present in all tumours, but 13 demonstrated mainly spindled cells and 19 demonstrated mainly lutein cells; 14 of the latter were from pregnant patients. The stroma was typically oedematous or collagenous, but in 14 cases was prominently hyalinised and, in four, myxoid. Prominent vascularity was present in most cases. The mitotic rate ranged from 0 to 8/10 high-power fields (HPF), but most demonstrated <1/10 HPF.

CONCLUSIONS

The differential diagnosis of SST is broad, including fibromas, thecomas, solitary fibrous tumours, pregnancy luteomas, myxomas, other ovarian sex cord-stromal tumours with sclerosis and, rarely, Krukenberg tumours. Strict adherence to the requirement of pseudolobulation, prominent (usually ectatic) vessels, and lutein cells and fibroblasts admixed in a jumbled manner, will distinguish the neoplasm from others in the differential.

Risk Assessment in Solitary Fibrous Tumor of the Uterine Corpus: Report of a Case and Systematic Review of the Literature

Solitary fibrous tumor (SFT) is an uncommon fibroblastic tumor occurring preferentially in the pleura, with a variable clinical course. SFT can arise also in numerous extrathoracic sites and very rarely in the female genital tract, with only scarce reports of uterine SFT. We reported a new uterine SFT arising in a 45-year-old woman, and we performed a systematic review of SFT cases of the uterine corpus interrogating the electronic databases PubMed, Web of Science, and Scopus. We identified only 13 patients diagnosed with SFT of the uterine corpus, including our one. Complete clinical workout at disease presentation showed no evidence of extrauterine spread in all cases, except for 1 patient who presented with metastatic disease. Tumor recurrences/metastases occurred in a minority of the patients and were poorly related to clinicopathological risk factors and patients stratification based on different scoring systems. Since the long-term clinical behavior of uterine SFT is limited and poorly predictable, extended follow-up is recommended also for all cases arising in the uterine corpus.

STAT6: A review of a signaling pathway implicated in various diseases with a special emphasis in its usefulness in pathology

Signal Transducer and Activator of Transcription 6 (STAT6), belonging to a family of seven similar members is primarily stimulated by interleukin(IL)-4 and IL-13, and acts as a T helper type 2 (Th2)-inducing factor. Thus, it is implicated in the pathophysiology of various allergic conditions, such as asthma, atopic dermatitis, eosinophilic esophagitis and food allergies, but also in tumor microenvironment regulation. Furthermore, certain forms of lymphomas, notably the Hodgkin lymphoma group, the primary mediastinal and primary central nervous system lymphoma, as well as some follicular and T cell lymphomas are associated with dysregulation of the STAT6 pathway. STAT6 immunohistochemical expression also serves as a surrogate marker in the diagnosis of solitary fibrous tumor, despite not directly responsible for the tumorigenic effect. These pathophysiological implications of the STAT6 pathway, its diagnostic or prognostic role in pathology, as well its immunohistochemical detection with different antibodies will be discussed in this review.

An abdominal-sacral approach with preoperative embolisation for vulvar solitary fibrous tumour: a case report

Background

Solitary fibrous tumours (SFTs) in the female genital tract are uncommon. Resection of these tumours is controversial because it can cause life-threatening haemorrhage. We report a case of vulvar SFT that was excised in a combined abdominal-sacral approach after preoperative embolisation.

Case presentation

At another hospital, an inoperable intrapelvic tumour was diagnosed in a 34-year-old woman. Computed tomography and magnetic resonance imaging showed that the uterus, urinary bladder and rectum were compressed laterally by a pelvic tumour with a maximum diameter of 11 cm. This mass was hypervascular and had a well-defined border. Transperineal biopsy was performed, and immunostaining revealed that the mass was an SFT. The tumour was supplied by feeding vessels from the right iliac arteries. First, we embolised the feeding vessels. Second, we performed surgical resection in a combined abdominal-sacral approach; no blood transfusion was necessary, and no perioperative complications occurred. The final pathological diagnosis was SFT that was positive for CD34 and signal transducer and activator of transcription 6 according to immunohistochemical staining.

Conclusion

During a year of follow-up, the disease did not recur. Treatment of pelvic SFT should aim at complete resection through various approaches after careful measures are taken to prevent haemorrhage.

Synovial Sarcoma of the Female Genital Tract: A Protean Mimic of Müllerian Neoplasia

Synovial sarcoma most commonly occurs in the extremities but has rarely been described in the female genital tract. In this series, we describe the clinical, morphologic, immunohistochemical, and molecular features of 7 cases of vulvovaginal synovial sarcoma (vulva, n=6; vagina, n=1). We emphasize their wide morphologic spectrum, which can overlap significantly with other more common tumors at these sites, as highlighted by 2 cases initially diagnosed as other entities (endometrioid carcinoma and malignant peripheral nerve sheath tumor). The average patient age was 41 (range: 23 to 62) years and tumor size ranged from 0.8 to 7 cm. Histologically, the tumors were biphasic (n=6) and monophasic (n=1). All cases were confirmed with fluorescence in situ hybridization or sequencing, and 5/5 cases were positive for the novel immunohistochemical markers SSX and SS18-SSX. In 3 cases with follow-up, 2 patients died of disease and 1 was alive with no evidence of disease. Previously described cases arising in the female genital tract are also reviewed. Vulvovaginal monophasic synovial sarcoma raises a broad differential diagnosis, including smooth muscle tumors, spindled carcinomas, and melanoma. Biphasic synovial sarcoma may mimic Müllerian carcinosarcoma, endometrioid carcinoma with spindled, corded, and hyalinized elements, and mesonephric-like adenocarcinoma. Awareness that synovial sarcoma can occur in the female genital tract with a wide variety of histologic appearances is critical for correctly diagnosing this rare entity. In particular, synovial sarcoma should be considered for any deeply situated "adenocarcinoma" in the vulva, with attention to subtle spindle cell differentiation.

Undifferentiated and dedifferentiated neoplasms of the female genital tract

Undifferentiated neoplasms in the female gynecologic tract comprise two main groups-undifferentiated carcinoma, most common in the endometrium and ovary, and undifferentiated uterine sarcoma, although tumors with an undifferentiated appearance may occur in all gynecologic organs. Their differential diagnosis is broad and generous sampling, careful morphological evaluation, judicious use of immunohistochemistry, and in many cases, molecular testing is often essential in the diagnostic work-up. As some of these neoplasms fail to respond to conventional chemotherapy regimens and/or radiation therapy, targeted therapy may be valuable in treating these highly aggressive tumors, thus the importance of precise diagnosis. In this review we discuss the clinicopathological features of undifferentiated carcinoma, dedifferentiated carcinoma, and undifferentiated uterine sarcoma, followed by a comprehensive analysis of morphological mimickers. Finally, we briefly review ovarian and lower genital tract tumors with an undifferentiated histological appearance.

NTRK and other recently described kinase fusion positive uterine sarcomas: A review of a group of rare neoplasms

The landscape of uterine sarcomas has greatly expanded in recent years to include neoplasms with recurrent gene fusions, such as BCOR and YWHAE translocated high-grade endometrial stromal sarcomas. Sophisticated molecular techniques have also resulted in the description of "new" entities associated with recurrent kinase fusions involving NTRK and RET as well as COL1A1-PDGFB rearranged uterine sarcomas. These rare neoplasms will be discussed in this review, highlighting that some of the underlying molecular events are clinically actionable and potentially susceptible to targeted therapy. While relatively few of these neoplasms have been described to date, likely being previously lumped under the spectrum of undifferentiated uterine sarcoma, the number of cases will expand in the future given their recognition and the increasing availability of molecular testing. These neoplasms have overlapping morphology (often with a "fibrosarcoma-like" appearance) and immunohistochemical features, and are characterized by variable clinical outcomes. Although immunohistochemistry may assist in some cases, a definitive subclassification requires confirmatory molecular studies. As these molecular assays may not be routinely available in most laboratories, referral to reference centers may be needed. In order to assist the pathologist, we suggest a diagnostic algorithm for routine practice when dealing with a malignant or potentially malignant uterine spindle cell neoplasm.

Solitary Fibrous Tumor of the Vulva: Case Report of a Rare Entity and Review of Literature

Solitary fibrous tumor (SFT) is an uncommon mesenchymal tumor of fibroblastic origin, which shows a prominent hemangiopericytoma-like branching pattern. It may be found at any location and can rarely involve the female genital tract with the vulva being the most common site of involvement. This is a case report of vulvar SFT in a 47-yr-old female who presented with a slow growing vulvar mass for 3 yr. Histologic examination showed a neoplasm composed of ovoid to spindle shaped cells with hypocellular and hypercellular areas in a collagenous background. Prominent hemangiopericytoma-like vessels were identified. Immunohistochemistry showed positive staining of the tumor cells for CD34, STAT6, ER, PR, and vimentin. Immunoshistochemical staining for desmin, SMA, and S100 was negative. The majority of SFTs have a NAB2-STAT6 gene fusion on chromosome 12, resulting in nuclear STAT6 overexpression, which is a sensitive and specific immunohistochemical marker for its diagnosis. Only 25 cases of vulvar SFT have been reported in the English literature and it should be considered in the differential diagnosis of spindle cell lesions at this site.

Gynecological Sarcomas: Molecular Characteristics, Behavior, and Histology-Driven Therapy

Gynecological sarcomas represent 3% to 4% of all gynecological malignancies and 13% of all sarcomas. The uterus is the most frequent primary site (83%); less frequently sarcomas are diagnosed originating from the ovary (8%), vulva and vagina (5%), and other gynecologic organs (2%). As the classification of gynecologic sarcomas continues to diversify, so does the management. Accurate histopathologic diagnosis, utilizing appropriate ancillary immunohistochemical and molecular analysis, could lead to a more personalized approach. However, there are subtypes that require further definition, with regard to putative predictive markers and optimal management. The aim of this review is to highlight the importance of accurate diagnosis and classification of gynecologic sarcoma subtypes by the surgical pathologist in order to provide more tailored systemic treatment, and to highlight the increasing importance of close collaboration between the pathologist and the oncologist.

Mesenchymal lesions of the vulva

Mesenchymal lesions of the vulva include site-specific entities limited to the lower genital tract, as well as a range of non-site-specific tumors that are more common at extragenital sites. Site-specific lesions include fibroepithelial stromal polyp, cellular angiofibroma, angiomyofibroblastoma, and aggressive angiomyxoma. Non-site-specific tumors that may occur in the vulva include those of smooth muscle, skeletal muscle, vascular, neural, adipocytic, and uncertain differentiation. This review discusses both site-specific and non-site-specific vulvar mesenchymal lesions including non-neoplastic proliferations, benign neoplasms, locally aggressive neoplasms with a predilection for local recurrence, neoplasms of indeterminate biologic potential, and frankly malignant neoplasms with a high risk of distant metastasis and death. Accurate diagnosis is essential for proper management, and is facilitated by correlation with clinical findings and targeted application of immunohistochemical and molecular studies.

Plexiform Neurofibroma of the Uterus: A Case Report

The female genital tract system is rarely affected by neurofibromatosis type 1 (NF1). Plexiform neurofibromas are congenital lesions that occur in patients with NF1. The vulva is the most frequent genital location but vaginal, cervical, uterine, and ovarian neurofibromas have rarely been reported. We describe a case of plexiform neurofibromas involving the uterine cervix in a patient with known NF1 that presented with chronic pelvic pain and heavy menstrual bleeding.

Clinico-pathological features of gynecological myopericytoma: a challenging diagnosis in an exceptional location

Myopericytomas (MPC) are rare mesenchymal tumors, originating from the perivascular myoid cells. They predominantly occur in the skin and superficial soft tissues of the extremities, while visceral involvement is rare. Histological features and clinical course are usually benign. To the best of our knowledge, MPC is still an uncharacterized tumor entity of the female internal genital tract. We describe three MPC cases involving the female internal genital tract: (1) a uterine wall MPC arising in a 49-year-old woman with progressive pelvic/abdominal pain; (2) a cervix MPC of a 49-year-old woman who presented with metrorrhagia, and (3) a MPC presenting as a simple ovarian cyst in a 26-year-old woman with pain located in the left iliac fossa. All patients were surgically treated, and recurrence occurred in two cases. The histological and immunohistochemical findings, supporting the diagnosis of MPC, are presented; in particular, one case showed characteristics pointing towards an uncertain biological behavior/low-grade malignancy. A literature search was conducted to identify previous reports of gynecological MPC and for possible alternative diagnoses. Leiomyoma, epithelioid leiomyoma, angioleiomyoma, perivascular epithelioid cell tumor, solitary fibrous tumor, and low-grade endometrial stromal sarcoma should be considered in the differential diagnosis. Awareness of possible occurrence of this rare neoplasm in the female genital tract is important to reach a correct diagnosis in the spectrum of mesenchymal tumors. Considering the risk of recurrence, we recommend careful evaluation of surgical margins and complete surgical removal whenever possible.

Ovarian Sex Cord-Stromal Tumors: Reflections on a 40-Year Experience With a Fascinating Group of Tumors, Including Comments on the Seminal Observations of Robert E. Scully, MD

CONTEXT.—

This year being the 60th anniversary of the publication of the excellent book Endocrine Pathology of the Ovary by John McLean Morris, MD, and Robert E. Scully, MD, the writer reflects on that work and in particular the remarkable contributions of its second author to our knowledge in this area.

OBJECTIVE.—

To review ovarian sex cord-stromal tumors.

DATA SOURCES.—

Literature and personal experience.

CONCLUSIONS.—

The essay begins with remarks on the oftentimes straightforward stromal tumors of the ovary because the commonest of them, the fibroma, dominates from the viewpoint of case numbers. Then, the sclerosing stromal tumor and the peculiar so-called luteinized thecomas of the type associated with sclerosing peritonitis are discussed in greater detail and their wide spectrum is illustrated. Brief mention is made of 2 rare neoplasms: the ovarian myxoma and signet-ring stromal tumor. Discussion then turns to the more recently recognized intriguing tumor tentatively designated microcystic stromal tumor and the commonest malignant tumor in this entire family, the so-called adult granulosa cell tumor, which despite its name may occasionally be seen in young individuals. The second variant of granulosa cell tumor-that which usually, but not always, occurs in the young-the so-called juvenile granulosa cell tumor, is then discussed. In the section of Sertoli-Leydig cell tumors, particular attention is focused on unusual tumors with heterologous elements and the remarkable so-called retiform tumors, which have a predilection for the young, often have distinctive gross features, and exhibit slitlike spaces and papillae. The essay concludes with consideration of the sex cord tumor with annular tubules.

Uterine and vaginal sarcomas resembling fibrosarcoma: a clinicopathological and molecular analysis of 13 cases showing common NTRK-rearrangements and the description of a COL1A1-PDGFB fusion novel to uterine neoplasms

Mesenchymal neoplasms of the uterus (corpus and cervix) encompass a heterogeneous group of tumors with differing morphologies, immunophenotypes and molecular alterations. With the advent of modern molecular techniques, such as next generation sequencing, newly defined genetic abnormalities are being reported in this group of neoplasms. Herein we report the clinicopathological and molecular features of a series of 13 spindle cell sarcomas of the uterus and vagina (10 cervix, 2 uterine corpus, 1 vagina) with morphology resembling fibrosarcoma. After targeted RNA-sequencing, dual FISH fusion and array-CGH analysis, 7 of 13 tumors exhibited NTRK rearrangements (6 TPM3-NTRK1 and 1 EML4-NTRK3) and 3 a COL1A1-PDGFB fusion; in the other 3 neoplasms, all of which were positive with S100 (2 diffuse, 1 focal), we identified no rearrangement. All the NTRK fusion-positive sarcomas were located in the cervix and exhibited diffuse staining with Trk while all the other neoplasms were negative. CD34 was diffusely positive in all 3 of the COL1A1-PDGFB fusion sarcomas. The latter molecular abnormality is identical to that commonly found in dermatofibrosarcoma protuberans and has not been reported previously in uterine mesenchymal neoplasms. We suggest that uterine sarcomas with a morphology resembling fibrosarcoma (and in which leiomyosarcoma and the known molecularly confirmed high-grade endometrial stromal sarcomas have been excluded) can be divided into 3 groups:- an NTRK fusion group, a COL1A1-PDGFB fusion group and a group containing neither of these molecular abnormalities which, on the basis of positive staining with S100, could be tentatively classified as malignant peripheral nerve sheath tumor, although additional molecular studies may identify specific genetic alterations necessitating a nomenclature change. We suggest a diagnostic algorithm when reporting such neoplasms. Identification of these newly described fusion-associated sarcomas is important given the potential for targeted treatments.

Solitary fibrous tumor/hemangiopericytoma of the penis

Solitary fibrous tumor/hemangiopericytoma (SFT-HMP) is a rare spindle-cell mesenchymal tumor, thought to be of myofibroblastic origin. Penile SFT-HMP was mentioned in the literature in two separate case reports which were published in 2015 and 2017. We present the first case of SFT-HMP which is localized on corpus cavernosum of the penis. A 55-year-old man presented to our clinic with a small and gradually growing lesion on his penis for the past year, which recently caused difficulties during sexual intercourse. On physical examination; a well-shaped, nodular non-fluctuant, solid, painless mass, measuring 4×4 cm was palpated. Magnetic resonance imaging showed 5×5 cm mass located on the right corpus cavernosa. Under spinal anesthesia, surgical excision was performed. Pathologically, the tumor had an irregular architecture patterns and was characterized by hypercellular areas separated by thin-walled, branching vessels, lined with a single layer of flattened endothelial cells. SFT-HMP rarely occurs in genital tract and penile presentation is among the rarest. It should be classified and considered under penile masses, especially if the mass is well circumscribed, painless and slowly growing in nature. After differential diagnosis, surgical excision is mandatory.

Solitary fibrous tumor

Solitary fibrous tumor (SFT) is a rare tumor of mesenchymal origin that account for less than 2% of all soft tissue masses. Initially identified in the pleura, SFT has been identified in multiple anatomic locations and can arise anywhere in the body. The varying histologic features along with non-specific means of identification have led SFT to be associated with several different names. Over the last several decades, sustained advances through research and technology have led to more reliable methods for differentiating this distinct soft tissue tumor. Advances specifically in immunohistochemistry and molecular diagnostics have identified CD34 as the most consistent marker in SFT, however even this lacks specificity to conclusively narrow down the broad differential for exact identification. More recently the discovery of the NAB2-STAT6 fusion gene has led to more precise diagnosis of SFT. Like many other soft tissue tumors, surgical management is the mainstay of treatment for SFT with emphasis on obtaining tumor-negative margins. Radiation therapy and chemotherapy regimens have not demonstrated global effectiveness, and thus no standardized treatments have been identified. Given the rarity of SFT and current supportive evidence for therapies, management should be focused on tumor extirpation. Nonetheless, individualized therapy, determined within a multidisciplinary setting should be considered.