Pleomorphic Rhabdomyosarcoma of the Uterine Corpus: A Clinicopathologic Study of 4 Cases and a Review of the Literature:

The "Other" Uterine Mesenchymal Neoplasms: Recent Developments and Emerging Entities

Uterine mesenchymal neoplasms are a challenging group of tumors that often show overlapping morphologic features and immunohistochemical profiles. The increasing use of molecular testing in these tumors has enabled a better appreciation of their pathobiology, resulting in a wave of emerging neoplasms and improved characterization of ones previously considered exceptionally rare. Identification of specific molecular alterations has permitted targeted therapy options in tumors that were typically unresponsive to conventional therapies, as well as recognition that a subset can have a hereditary basis. This review will discuss the more "common" of the uncommon uterine mesenchymal neoplasms, including inflammatory myofibroblastic tumor, perivascular epithelioid cell tumor, uterine tumor resembling ovarian sex cord tumor, and embryonal rhabdomyosarcoma. This will be followed by an overview of emerging entities, including NTRK -rearranged uterine sarcoma, SMARCA4 -deficient uterine sarcoma, KAT6B/A::KANSL1 fusion uterine sarcoma, and MEIS1::NCOA2/1 fusion sarcoma.

A rare adult case of primary uterine rhabdomyosarcoma with mixed pattern: a clinicopathological & immunohistochemical study with literature review

BACKGROUND

Rhabdomyosarcomas are aggressive tumors that comprise a group of morphologically similar but biologically diverse lesions. Owing to its rarity, Mixed pattern RMS (ARMS and ERMS) constitutes a diagnostic and therapeutic dilemma.

CASE

Herein is presented a very rare case of mixed alveolar & embryonal rhabdomyosarcoma in the uterus of a 68-year-old woman. The wall of the uterine corpus & cervix was replaced by multiple whitish-yellow, firm nodules, measuring up to 12 cm. Microscopically, the tumor was predominantly composed of round to polygonal cells arranged in nests with alveolar pattern intermingled with hypo- & hypercellular areas of more primitive cells with scattered multinucleated giant cells seen as well. Extensive sampling failed to show epithelial elements. Immunohistochemical staining showed positive staining for vimentin, desmin, myogenin, CD56 & WT-1. However, no staining was detected for CK, LCA, CD10, ER, SMA, CD99, S100, Cyclin-D1 & Olig-2. Metastatic deposits were found in the peritoneum. The patient received postoperative chemotherapy and radiotherapy but died of systemic metastases 3 months after surgery.

CONCLUSION

The rarity of this histological tumor entity and its aggressive behavior and poor prognosis grab attention to improving recognition and treatment modalities in adults.

Pleomorphic Rhabdomyosarcoma: A Systematic Review with Outcome Analysis and Report of a Rare Abdominal Wall Lesion

Introduction. Pleomorphic rhabdomyosarcoma (RMS) is an aggressive and rare malignant neoplasm with a poor prognosis. As its name suggests, this tumor exhibits extensive pleomorphism with features of skeletal muscle differentiation. Due to its rarity, its diagnosis is often a clinical and pathological challenge. Since only small case series and a few scattered case reports exist in the literature, the impact of different demographic features, tumor site, and/or treatment modality on patient outcomes has yet to be extensively studied. Methods. We report a case of a pleomorphic RMS presenting atypically as an abdominal wall mass. We have also analyzed the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) database to determine the factors affecting the outcome of this neoplasm. Moreover, we present a review and summary of pleomorphic RMS cases arising from the abdominal wall reported in the English language literature. Results. We found two hundred and forty-two cases of pleomorphic RMS in the SEER database. The majority of the patients were diagnosed after the age of 40, with the age of diagnosis showing a unimodal distribution. The majority of the patients were Caucasian (82%) and male (59%). Age of diagnosis, tumor stage, and surgical management significantly affected the patients' outcome, while patients' ethnicity, sex, or tumor site did not affect the outcome. We only found five previously reported cases of pleomorphic RMS arising from the abdominal wall. Conclusions. Pleomorphic RMS arising from the abdominal wall is extremely rare. Our data sheds light on the factors affecting the outcome of pleomorphic RMS. We have also discussed the challenges involving the histopathological diagnosis of this rare neoplasm and how to best approach this task.

Rhabdomyosarcoma of the uterus in an adult patient with osteopetrosis: a case report

Background

Uterine sarcoma accounts for 3–7% of uterine malignant neoplasms. It is more aggressive than epithelial neoplasms, and patients have a poor prognosis. Rhabdomyosarcoma is classified as a heterologous uterine sarcoma. It is the most common soft tissue malignancy in children while rare in adults. In young patients, the majority of genital tract rhabdomyosarcomas occur in vagina; however, the most common site of gynecologic rhabdomyosarcoma is cervix followed by uterine corpus, in adults. Uterine corpus rhabdomyosarcoma is rare in adults. Diagnosis of pure rhabdomyosarcoma in uterus involves widespread and perfect sampling as well as precise histopathological evaluation to uncover any epithelial component.

Case presentation

Here we report a case of pure rhabdomyosarcoma of uterine corpus in a 60-year-old Iranian postmenopausal female who had osteopetrosis, presenting with 8-month heavy vaginal bleeding and a protruding cervical mass. She is alive on 18-month follow-up after treatment.

Conclusions

Rhabdomyosarcoma of uterine corpus is rare in adults. Diagnosis of pure rhabdomyosarcoma in uterus involves widespread and perfect sampling as well as precise histopathological evaluation to uncover any epithelial component. Treatment options in adult gynecological rhabdomyosarcoma are based on studies in younger patients, and more studies may help us choose the best approach for improving outcome.

Embryonal rhabdomyosarcoma of the uterine corpus: a clinicopathological and molecular analysis of 21 cases highlighting a frequent association with DICER1 mutations

Herein we evaluated a series of 21 embryonal rhabdomyosarcomas of the uterine corpus (ucERMS), a rare neoplasm, to characterize their morphology, genomics, and behavior. Patients ranged from 27 to 73 (median 52) years and tumors from 4 to 15 (median 9) cm, with extrauterine disease noted in two. Follow-up (median 16 months) was available for 14/21 patients; nine were alive and well, four died of disease, and one died from other causes. Most tumors (16/21) showed predominantly classic morphology, comprised of alternating hyper- and hypocellular areas of primitive small cells and differentiating rhabdomyoblasts in a loose myxoid/edematous stroma. A cambium layer was noted in all; seven had heterologous elements (six with fetal-type cartilage) and eight displayed focal anaplasia. The remaining five neoplasms showed only a minor component (≤20%) of classic morphology, with anaplasia noted in four and tumor cell necrosis in three. The most frequent mutations detected were in DICER1 (14/21), TP53 (7/20), PI3K/AKT/mTOR pathway (7/20), and KRAS/NRAS (5/20). Copy-number alterations were present in 10/19 tumors. Overall, 8/14 DICER1-associated ucERMS showed concurrent loss of function and hotspot mutations in DICER1, which is a feature more likely to be seen in tumors associated with DICER1 syndrome. Germline data were available for two patients, both DICER1 wild type (one with concurrent loss of function and hotspot alterations). DICER1-associated ucERMS were more likely to show a classic histological appearance including heterologous elements than DICER1-independent tumors. No differences in survival were noted between the two groups, but both patients with extrauterine disease at diagnosis and two with recurrences died from disease. As no patients had a known personal or family history of DICER1 syndrome, we favor most DICER1-associated ucERMS to be sporadic.

Diagnosis and treatment of pleomorphic rhabdomyosarcoma of the uterus: a rare case report and review of the literature

Pleomorphic rhabdomyosarcomas of the uterus (PRMSu) is a rare malignant tumor of the female genital tract. Accurate diagnosis and effective treatment of PRMSu are important. We report an 81-year-old woman who was diagnosed with PRMSu. She had an extremely unusual presentation of secondary dyspnea because of an extremely large uterus (26.0 cm). Pelvic magnetic resonance imaging showed rare severe enlargement and intrauterine filling with tumor tissue, and she was initially diagnosed with uterine leiomyosarcoma. The patient underwent hysterectomy, as well as bilateral salpingo-oophorectomy and omentectomy, and was finally confirmed as having PRMSu by histopathology combined with immunohistochemistry. We performed a systematic review of the literature between 1982 and 2020 and focused on different treatment strategies and prognosis of PRMSu. A retrospective review of 28 cases was conducted and survival analysis was estimated by using the Kaplan–Meier method. We found that the accuracy of diagnosis of PRMSu completely depends on histopathology and immunohistochemistry because of no special clinical symptoms, no sensitive tumor markers, and no special imaging findings. Although there is no standardized approach for treating this rare disease, the treatment strategy of a surgical operation combined with adjuvant chemotherapy appears to be the best choice.

High-grade uterine sarcoma with osteosarcomatous differentiation arising from a MED12-mutated leiomyoma, a case report

Uterine osteosarcoma has been reported, but it is an extremely rare tumor with highly aggressive behavior and poor prognosis. The pathogenesis of uterine osteosarcoma is not fully understood. Herein, we report on a high-grade uterine sarcoma with focal osteosarcomatous differentiation that developed from a long-standing MED12-mutated leiomyoma. A 47-year-old nulligravida woman, with known uterine leiomyoma presented with abdominal pain and distention. Imaging analyses revealed a tumor with a large cystic area in the uterine corpus and multiple metastases in intrapelvic and paraaortic lymph nodes, left ovary and left lung. With a clinical diagnosis of uterine sarcoma the patient underwent abdominal total hysterectomy, bilateral salpingo-oophorectomy, partial omentectomy and removal of the left obturator lymph node. Despite postoperative chemotherapy and radiation therapy, the tumor progressed rapidly. She died 18 weeks after the surgery. Histopathologic examination identified a high-grade pleomorphic sarcoma in which focal osteoid production was observed. This high-grade sarcoma with focal osteosarcomatous differentiation was located within the uterine leiomyoma, and Sanger sequencing showed the identical MED12 L36R mutation in both the osteosarcomatous and leiomyomatous components supporting the shared origin of these two components. We, therefore, concluded that the high-grade sarcoma with osteosarcomatous differentiation arose from the transformation of the precedent leiomyoma.

Uterine metastatic rhabdomyosarcoma in a scimitar-horned oryx (Oryx dammah)

A 13-year-old female scimitar-horned oryx (Oryx dammah) died after progressive anorexia, weight loss, and depression. The necropsy showed that the retroperitoneum was compressed by a large white-to-tan uterine mass and on several sections of the mass, the uterine wall was markedly thickened because of ill-defined transmural tumor tissue. Metastatic nodules were detected in the omentum, mesentery, diaphragm, and lung. The genital tract and pulmonary and abdominal nodules exhibited highly pleomorphic sarcoma. The primary and metastatic neoplastic cells showed positive results for vimentin, desmin, and sarcomeric actin, and negative results for smooth muscle actin. Uterine metastatic rhabdomyosarcoma was diagnosed on the basis of the gross, histopathology and immunohistochemistry results.

Uterine rhabdomyosarcoma in adults

Rhabdomyosarcoma (RMS) is an aggressive mesenchymal tumor most commonly diagnosed in the pediatric population, and when occurring in adults, tends to develop in the deep soft tissue of the limbs. Primary uterine RMS comprises an even more restricted subset, with little known or reported when compared to most other gynecologic sarcomas. Our goal with this study was to retrospectively evaluate cases from two academic institutions and describe the main histopathologic findings of this rare gynecologic malignancy. A total of 8 cases were identified, consisting of 4 pleomorphic rhabdomyosarcomas (PRMS), 2 alveolar rhabdomyosarcomas (ARMS), and 2 embryonal rhabdomyosarcomas (ERMS). They occurred in patients ranging from 22 to 70 years old, and the most common presenting symptom was vaginal bleeding. Most patients presented with advanced stage at diagnosis, including metastatic disease to lymph nodes and to distant sites. The masses were mostly (6/8) centered in the myometrium, while two cases arose in the cervix (2/8). Histologic characteristics of the tumors were dependent on the RMS subtype, although all cases demonstrated a similar immunohistochemical profile regardless of their subclassification. RMS of the uterus has a very poor prognosis, and data regarding treatment of this rare malignancy is limited, and usually extrapolated from non-uterine sites.

Giant Cell Tumor of the Uterus: A Report of 3 Cases With a Spectrum of Morphologic Features

Giant cell tumors, a well-recognized neoplasm of bone, can rarely be found in the uterus. Such tumors are characterized by a dual population of mononuclear and osteoclast-like giant cells that lack epithelial and specific mesenchymal differentiation. In this study, the clinicopathologic features of 3 giant cell tumors of the uterus were reviewed. Immunohistochemistry for CD68, CD163, h-caldesmon, desmin, SMA, AE1/AE3, CD10, ER, PR, cyclin D1, CD1a, CD34, CD30, S100, myogenin/myoglobin, and Ki-67 was performed in all tumors, along with ultrastructural analysis in one. The patients were 47, 57, and 59 yr and the tumors measured 2.5, 7.5, and 16.0 cm. One neoplasm was confined to the endometrium, whereas the other 2 were myometrial. All 3 tumors showed a nodular growth comprised of mononuclear and osteoclast-like giant cells. The endometrial-confined tumor consisted of histologically benign mononuclear cells, whereas the others exhibited marked atypia. Mitotic activity was up to 5/10 HPF in the benign tumor and up to 22/10 HPF in the malignant. No cytologic atypia or mitoses were observed in the giant cells. CD68 and CD10 were strongly and diffusely expressed in both components of 3 and 2 neoplasms, respectively. Cyclin D1 was focal in the mononuclear cells and focal to diffuse in the giant cells. CD163 was diffuse in the mononuclear cells, but absent to focal in the giant cells. Ultrastructural analysis lacked diagnostic features of epithelial or specific mesenchymal differentiation. Both malignant tumors demonstrated an aggressive behavior. In summary, although rare, giant cell tumor of the uterus should be included in the differential diagnosis of benign or malignant tumors containing osteoclast-like giant cells.

Misdiagnosis of primary pleomorphic rhabdomyosarcoma of the right thigh in a young adult: A case report

Pleomorphic rhabdomyosarcoma (PRMS) is a rare type of soft tissue tumor accounting for <2% of all adult sarcomas. The present study describes a case of a 28-year-old male patient with primary PRMS of the right thigh. The patient was initially diagnosed with a schwannoma and underwent conservative therapy at a local hospital. At the 6-month follow-up, the patient reported a marked increase in the size of the mass. Finally, the patient underwent fine-needle aspiration and total tumor resection. The tumor measured 11×9×5 cm3 in size and was located in the vastus intermedius muscle. According to histological and immunohistochemical findings, a diagnosis of PRMS was confirmed by an expert pathology consultant. Postoperative follow-up at 3 months revealed no evidence of recurrent disease or residual side effects from therapy. However, it is imperative that such cases are closely monitored following surgery, in order to evaluate the long-term efficacy of the procedure, since misdiagnosis may increase the risk of recurrence and metastasis. The present case is noteworthy due to the misdiagnosis of PRMS, the large size of the mass and the young age of the patient.

Uterine leiomyomas with bizarre nuclei: a clinicopathologic study of 59 cases

Leiomyoma with bizarre nuclei (LM-BN) is an uncommon tumor with histologic features (mononucleated or multinucleated bizarre cells that may have a diffuse distribution, prominent nucleoli, and karyorrhectic nuclei that may mimic atypical mitoses) that often causes confusion with leiomyosarcoma. Fifty-nine LM-BNs were collected from our consultation files over the years 2000 to 2011. Features recorded included patient age, therapy, tumor size, border, gross appearance, density and distribution of BN, mitotic count, karyorrhectic nuclei, prominent nucleoli, cells with conspicuous dense eosinophilic cytoplasm (rhabdoid-like), vascular changes and type of vasculature, and presence of necrosis and its nature. Follow-up information was obtained for all patients. Patients ranged in age from 25 to 75 (average 45) years (11 patients between 25 and 35 y, 20 between 36 and 45 y, 22 between 46 and 55 y, and 6 between 56 and 75 y). Forty-two underwent hysterectomy and 17 myomectomy. For 51 tumors gross findings were known. Forty (78%) had a solid white and whorled cut surface and 11 (22%) a yellow appearance. Five (10%) neoplasms showed prominent cystic degeneration, and hemorrhage and/or necrosis was seen in 9 (18%). Forty-five LM-BNs had a pushing margin with the surrounding myometrium, whereas 1 showed irregular borders. Margins could not be ascertained in the slides available in 13 cases. Twenty-eight (48%), 19 (32%), and 12 (20%) LM-BN showed low, intermediate, and high BN density. Eighteen (30%) tumors showed diffuse, 26 (44%) showed multifocal, and 15 (26%) had focal BN distribution. Mitotic counts ranged from 0 to 7/10 high-power fields (HPF) (average 1 to 2/10 HPF). Thirty-seven (63%) had <2/10 HPF, 19 (32%) had 2 to 5 mitoses/10 HPF, and in 3 tumors (5%) mitotic counts were 6, 7, and 7/10 HPF (2 with focal and 1 with diffuse BN). All but 4 LM-BNs showed karyorrhectic nuclei, striking in 12 neoplasms, mimicking atypical mitoses. Nineteen (32%) LMs had prominent eosinophilic nucleoli surrounded by a clear halo. Ischemic necrosis was detected in 21 (36%) LM-BN. Rhabdoid-like cells were noted in 24 (41%) tumors. All patients had no evidence of recurrence, ranging from 1 to 13 years (overall average 6 y; in patients with myomectomy 6.3 y with a range of 2.6 to 11 y). Our results corroborate that LM-BN is associated with a favorable outcome even in those patients only treated by myomectomy and highlights that a conservative approach can be undertaken in these patients, as many of them are of reproductive age. Because of the favorable outcome, the term LM-BN is preferable to alternative terminology including "atypical leiomyoma."

Use of immunohistochemistry in the diagnosis of miscellaneous and metastatic tumors of the uterine corpus and cervix

Uncommon tumors in the uterus present diagnostic challenges. In some cases, the tumor subtype is usually seen outside the gynecologic tract and the possibility of a uterine primary is not considered. In other cases, histologic overlap with more common uterine tumors leads to potential misdiagnosis. Finally, metastatic carcinoma may involve the uterus and cervix. Rarely, symptoms related to the uterine metastasis may precede diagnosis of an extrauterine primary. Without the proper clinical context, the possibility of a missed diagnosis is increased. One must first be aware of these possibilities, but immunoperoxidase studies are often necessary to confirm the diagnosis. In this review, unusual and metastatic tumors involving the uterine corpus and cervix and immunoperoxidase studies used to diagnosis such tumors are discussed.

Spindle cell rhabdomyosacoma of uterus: a case study

Uterine rhabdomyosarcoma (RMS) typically presents as a mixed epithelial and mesenchymal tumors. Pure RMSs of the female genital tract are uncommon. Spindle cell variant of RMS is a rare morphologic subtype of embryonal RMS and mostly occurs in the paratesticular region of children. Here, we present a case of uterine spindle cell RMS in a 76-year-old woman. The tumor, 20×15×7 cm in size, was highly necrotic and adherent to the colon and rectum. Tumor cells were mostly spindle-shaped, and isolated rhabdomyoblasts were scattered. Immunohistochemical stains for myoglobin and myo-D1 showed diffuse positivity for tumor cells. The patient died only of disease three months after diagnosis.

Embryonal rhabdomyosarcoma (botryoid type) of the uterine corpus and cervix in adult women: report of a case series and review of the literature

In its classical form, embryonal rhabdomyosarcoma (ERMS, botryoid type) is a vaginal neoplasm occurring in infants and young girls and is often not considered in the differential diagnosis of uterine corpus and cervical spindle cell tumors in adult women. Clinicopathologic and immunohistochemical features of 25 cases of ERMS in women 20 years of age or older were analyzed. Patient age ranged from 20 to 89 years (mean, 44.4 y; median, 46 y), with 8 patients aged 20 to 39 years, 14 patients aged 40 to 59 years, and 3 patients older than 60 years of age. Tumors originated in the cervix in 20 cases and in the uterine corpus in 5. They were characterized by an edematous hypocellular spindle cell proliferation, typically with cellular condensation beneath epithelial surfaces (cambium layer), in which tightly packed hypercellular foci were scattered. Neoplastic cells had hyperchromatic nuclei and minimal cytoplasm, usually with delicate cytoplasmic processes. Occasionally, elongated or globular cells with eosinophilic cytoplasm (rhabdomyoblasts) were evident, but cytoplasmic cross-striations were only rarely identified. Apoptotic bodies and mitotic figures were usually identified in the hypercellular foci. Hemorrhage was common, often making recognition of the hypercellular foci difficult. Desmin and myogenin were coexpressed in 22 of 23 (95.6%) tumors evaluated. Proliferative activity, as assessed by Ki-67 expression, was notably elevated in all tumors evaluated, typically concentrated in the hypercellular foci. Estrogen and progesterone receptors were expressed focally in only 3 of 12 (25%) and 1 of 8 (12.5%) tumors evaluated, respectively. Follow-up was available in 7 cases. Five patients were alive without evidence of disease with follow-up of 3 to 8 years, and 1 patient was alive with disease at 5 months. One patient died at 5 months with pulmonary nodules, but it was not determined whether this was due to metastatic ERMS or the patient's known ductal breast carcinoma. ERMS has a broader clinical profile than classically expected and should be considered in the differential diagnosis of a uterine corpus or cervical spindle cell tumor, regardless of patient age. Recognition can be rendered difficult by the hypocellular background, which can suggest a benign polyp or low-grade tumor, and hemorrhage, which can obscure the characteristic hypercellular foci. Identification of hypercellular foci in which mitotic activity and apoptotic bodies are found, desmin and myogenin are coexpressed, proliferative activity is notably elevated, and hormone receptor expression is usually absent is very useful for establishing the diagnosis.

Primary ovarian rhabdomyosarcoma in a dog

A 10-year-old female English pointer was diagnosed with an ovarian tumour with abdominal metastases. Ultrasonography revealed several nodules of 1-5 cm diameter within the abdominal cavity. Fine needle aspiration cytology of the nodules suggested a malignant mesenchymal tumour. On necropsy examination the right ovary and its capsule were enlarged and there were white-red, friable nodular masses distributed over the surface of the pancreas, liver, omentum, mesentery and serosae of the small and large intestines. Microscopical evaluation revealed neoplastic cells with a high degree of pleomorphism and vascular invasion. Immunohistochemically, the neoplastic cells expressed myosin, desmin, vimentin and CD10, but were negative for cytokeratin, placental alkaline phosphatase, inhibin-alpha and smooth muscle actin. Based on these findings a diagnosis of primary ovarian alveolar rhabdomyosarcoma was made.

Giant cell tumor of uterus resembling osseous giant cell tumor: case report and review of literature

Osteoclast-like giant cells (OLGCs) are multinucleated cells of histiocytic lineage and have been identified in a wide array of neoplasms. In the uterus, they have most frequently been reported in association with leiomyosarcomas. This article describes a case of an osteoclast-like giant cell-rich uterine tumor that was essentially indistinguishable at the morphologic and immunophenotypic levels, from typical giant cell tumor of bone. This is the first example of such a case that has been reported in the uterus to the authors' knowledge.

Heterologous and rare homologous sarcomas of the uterine corpus: a clinicopathologic review

Pure sarcomas of the uterine corpus are uncommon, constituting less than 3% of all malignancies at this site, and most of them are leiomyosarcomas and endometrial stromal sarcomas. Rare histotypes of homologous sarcomas and heterologous sarcomas are occasionally encountered, and the absence of significant accumulated experience with these histotypes at this location may potentially raise diagnostic and patient management difficulties. In this article, the clinicopathologic attributes of all earlier reported sarcomas of the uterine corpus other than leiomyosarcomas and endometrial stromal sarcomas are summarized. Included are embryonal rhabdomyosarcoma, pleomorphic rhabdomyosarcoma, angiosarcoma, alveolar soft part sarcoma, malignant perivascular epithelioid cell tumors (PEComas), osteosarcoma, chondrosarcoma, liposarcomatous tumors, malignant extrarenal rhabdoid tumors, Ewing sarcoma/primitive neuroectodermal tumor, and other rare histotypes. Embryonal rhabdomyosarcoma (20%), Ewing sarcoma/primitive neuroectodermal tumor (17%), angiosarcoma (14%), and pleomorphic rhabdomyosarcoma (13%) appeared to be more common than the others, although there was no single overwhelmingly prevalent histotype in the group. A subset, including embryonal rhabdomyosarcoma, alveolar soft part sarcoma, and PEComas, peak in the premenopausal years, but most of the others were observed in postmenopausal women. Favorable outcomes have been reported for the patients diagnosed with alveolar soft part sarcoma, and the prognosis for their counterparts with PEComa remains a matter of debate. Multimodal therapeutic approaches to contemporary patients with embryonal rhabdomyosarcomas have resulted in significantly improved outcomes. Unfortunately, most of the other sarcomas have been associated with rapid tumor progression and unfavorable patient outcomes. The differential diagnosis for these sarcomas is often extensive and varies by histotype, but their accurate diagnosis fundamentally requires the careful exclusion of biphasic malignancies.