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A rare spontaneous hepatic leiomyosarcoma with osteosarcomatous differentiation was observed in a female beagle dog and its morphological and immunohistochemical characteristics were examined. Upon necropsy, an endoceliac mass originating from the liver was detected, which was composed of hematoid fluid-filled cysts and white to grayish solid tissue. There were no macroscopic findings in other organ systems. Histopathologically, the hepatic mass consisted of two different mesenchymal components. One form was spindle cells arranged in interlacing fascicles immunohistochemically positive for smooth muscle actin (SMA) and smoothelin, indicating leiomyosarcomatous differentiation. The other form was composed of short spindle cells positive for S-100 and was producing various amounts of eosinophilic osteoid and trabecula-like matrices positive for osteocalcin, indicating osteosarcomatous differentiation. In addition, invasive growth in the hepatic parenchyma and cell atypia were observed. Based on these findings, the mass was diagnosed as hepatic leiomyosarcoma with osteosarcomatous differentiation (malignant mesenchymoma), which might be derived from undifferentiated mesenchymal cells.

Hepatic embryonal sarcoma is a malignancy classified among soft tissue tumors of uncertain differentiation. It is also known as liver embryonal sarcoma, embryonal sarcoma of the liver, undifferentiated embryonal sarcoma, malignant mesenchymoma of the liver, and mesenchymal sarcoma of the liver.

Composite sarcoma of bone is a very rare entity that primarily affects adolescent and young adult patients. It usually combines areas of liposarcoma and osteosarcoma, and up to 60% of cases have metastatic disease at diagnosis. It is a highly aggressive pathology with intrinsic resistance to bone sarcoma conventional treatments. The prognosis is poor, with long-term survival rates not exceeding 30%. We present the case of an adolescent female diagnosed with an aggressive composite sarcoma of bone with rhabdomyosarcoma foci and loco-regional lymph node involvement.

Introduction/Background Uterine leiomyosarcomas are a rare form of uterine tumours and are often associated with poor survival prognosis. Heterologous differentiation in leiomyosarcomas is an extremely rare phenomenon with less than 15 cases reported in literature to date. We report a case of primary myxoid leiomyosarcoma of the uterus with osteocartilaginous differentiation. Methodology A 44-year old Chinese female first presented to our hospital with complaints of irregular heavy periods and was found to have iron-deficiency anaemia. She underwent a dilatation and curettage which revealed a benign endometrial polyp on a background of late proliferative endometrium. A pelvic ultrasound was performed and she was found to have multiple uterine fibroids with the largest one measuring 4.8 cm. She opted for conservative management but repeated follow up scans showed the fibroid enlarging in size to 8.9 cm over a period of 2 years. In view of enlarging size of fibroid, she was advised for surgery and underwent a total abdominal hysterectomy and bilateral salpingo-oophorectomy. Results Final histology showed a malignant neoplasm with areas of myxoid leiomyosarcoma and smaller areas of osteosarcomatous and cartilaginous differentation, raising the possible differential diagnosis of malignant mesenchymoma arising from the uterus. She was discussed at the gynae-oncology tumour board meeting and conclusion favoured a myxoid leiomyosarcoma. She was offered complete surgical staging but she declined. Her post-operative CT scan of the chest, abdomen and pelvis was clear with no evidence of lymphadenopathy or distant metastasis. She has remained disease-free for 18 months so far. Conclusion Osteocartilaginous differentiation of a malignant uterine myxoid leiomyosarcoma is very rare and very few such cases have been reported in literature. This unique case emphasizes the importance of clinical correlation with radiological and pathological findings in confirming the diagnosis of tumours with unusual histology and presentation. Disclosure Nothing to disclose.

Liposarcoma is a rare malignant tumor of the origin of adipose tissue, with an incidence less than 1/1000000. We distinguish three types of tumors: benign (lipoma), intermedial (well-differentiated liposarcoma) and malignant (dedifferentiated liposarcoma, myxoid and pleomorphic liposarcoma). Dedifferentiated liposarcoma is a combination of fat and sarcoma cells. Its growth is slow, which makes early diagnosis difficult due to the absence of symptomatology. The tumor is aggressive with recurrences, metastasis and lethal outcomes, resistant to all therapeutic options except surgical treatment. The patient, 48 years old, hypertensive, overweight and a smoker, at the beginning of 2017 indicates an oval tumefaction on her right thigh, lateral side from middle of the femur to the knee, surrounded by cellulite and slowly increasing. The change is of solid structure, located under the skin above the knee. Echosonographically subcutaneous from half the femur to the knee vascularized tumorous formation, 80mm wide, which breaks the architecture of the fat, including the muscles. MRI scan shows a soft tissue infiltrative change, dominantly in the subcutaneous body fat. Shown to a vascular, reconstructive surgeon and orthopedist, the change appears to be a desmoid tumor and they indicate continuation of the treatment at a referenced institution. The tumor was surgically removed. Histopathologically is a high-grade primary malignant mesenchymoma, dedifferentiated liposarcoma, with leiomyoblastic differentiation. A pseudocapsule was infiltrated to the viable tumor cells and the Sarcoma consilium ordinates a postoperative radiotherapy (50 Greja-Gy in 25 fractions). Patient feels well and appears for regular check-ups. In order to successfully treat liposarcoma, a multidisciplinary approach of a surgeon, radiotherapist, pathologist, oncologist and a nuclear medicine specialist in specialized centers are necessary.

Malignant mesenchymoma is a rare tumor in which there are two or more distinct mesenchymal components. These are generally considered as high-grade neoplasms and are usually associated with a poor prognosis. Here, we report a case of malignant mesenchymoma containing undifferentiated spindle cell sarcoma, leiomyosarcoma, chondrosarcoma, osteosarcoma, and areas with rhabdoid differentiation in a 54-year-old male. The primary tumor measured 5.5 × 4 × 3 cm and weighed 135 g arising from the left submandibular salivary gland. Fine-needle aspiration cytology showed the presence of pleomorphic spindle cell clusters with atypia and myxoid stroma. An impression of malignant salivary gland neoplasm was given. Diagnosis of malignant mesenchymoma was made on histopathological examination supported by immunohistochemistry showing strong positivity with p53, Ki-67, and focal positivity for smooth muscle actin, S-100, desmin, and negativity for cytokeratins. The exact histogenesis of malignant mesenchymoma and the optimal management strategy to decide the prognosis remains uncertain as it is a rare tumor.

We have read with great interest the article written by Ko et al. [1] on a particularly rare type of malignant mesenchymal tumor, paratesticular leiomyosarcoma (LMS), and we appreciate the argumentation on the utility of adjuvant chemotherapy in treatment of stage III disease. As for our experience, we would like to shed light on a very rare and little-known aspect surrounding this neoplasm, which is the capability of dedifferentiation exerted in order to recur or metastasize. In 2007, a 56-year-old male underwent right orchifunicolectomy for a LMS of the spermatic cord. No metastasis was detected on preoperative whole body computed tomography scan. Histologically, the tumor measured 2.5 cm in diameter, was well differentiated (G1 with a Ki-67 index of 10%), had disease-free surgical margins and the result was composed of neoplastic spindle cells with elongated nuclei and prominent nucleoli arranged in interlaced fascicles; immunohistochemistry was positive for smooth muscle actin (SMA) and vimentin but negative for S100 protein. In 2012, a para-aortic and right external iliac lymphadenectomy was performed because of two centimetric lymph nodes showing a maximum standardized uptake value (SUVmax), respectively, of 14 and 4 on 18-fluoro-2-deoxyglucose positron emission tomography–computed tomography (18F-FDG PET-CT) scan (Fig. 1A): such metastases had the same histopathological features previously described for LMS (Ki-67 index of 10% and staining positive for SMA but negative for S100 protein) (Fig. 1B) and adjuvant epirubicin-ifosfamide was given for 4 months. In 2013, two centimetric nodules were removed from the perineal and sovrapubic area (SUVmax less than 2.0 on 18F-FDG PET-CT scan) (Fig. 2A). Histology showed that both specimens were adipose tissue neoplasms consisting of spindle cells with nuclei devoid of nucleoli interspersed with a few larger polynucleated elements as well as smaller cells with plump nuclei; immunohistochemistry yielded the diagnosis of metastatic soft tissue tumor, but, of interest, excluded the well differentiated leiomyosarcomatous in favour of a dedifferentiated liposarcomatous phenotype (G2, Ki-67 30%, SMA-negative but S100- and MDM2-positive) (Fig. 2B). Adjuvant radiotherapy was administered through five cycles and as of now the patient has been disease-free for 2 years. Of note, all pathologic verifications were performed at the same department of histopathology. Fig. 1. (A) 18-Fluoro-2-deoxyglucose positron emission tomography–computed tomography scan showed two right external iliac centimetric lymph nodes with an increased maximum standardized uptake value (of 14 and 4, red color with yellow halo). (B) Immunohistochemistry ... Fig. 2. (A) 18-Fluoro-2-deoxyglucose positron emission tomography–computed tomography scan detected two centimetric nodules in the perineal and sovrapubic area (maximum standardized uptake value less than 2.0, white color with green halo). (B) Histological ... Sarcomas of the spermatic cord are rare tumors including mostly liposarcomas (LPSs) (50% with 110 cases as of 2014) and LMSs (18%). Characterization is not simple because they sometimes present as hybrid tumors consisting of two or more cell lines of differentiation: such an occurrence has generated some confusion regarding the nomenclature as well as the assessment of pathobiological features of these neoplasms. The term malignant mesenchymoma (MM) has referred to different tumors through the years: currently, it indicates a sarcoma with two or more unrelated, differentiated malignant components, such as LPS or rhabdomyosarcoma combined with osteosarcoma [2]. When MM consists of a well-defined, low-grade LPS along with a less differentiated high-grade component (such as fibrosarcoma or malignant fibrous histiocytoma), the name dedifferentiated LPS (DDLS) should be used. DDLS can also present as heterologous areas of LMS in the dedifferentiated zone (DL-LMS). When the biphasic pattern of MM is represented by the synchronous or metachronous coexistence of LPS with LMS, the term lipoleiomyosarcoma (L-LMS) should be preferred [2]. Of note, only 11 cases of paratesticular L-LMS exist to date [3-5]. Histologically, MMs differ from DDLSs because the two components are intermingled whereas in the latter they can be sharply distinguished from each other. Both L-LMS and DL-LMS have a poor prognosis: the former tends to recur, the latter to metastasize. As for our case, since both the original and recurrent cancer did not contain undifferentiated cell elements, we consider it an instance of MM rather than a DDLS. And, differently from the other reported instances of L-LMS, our case showed an inverse temporal sequence of the histological patterns (LMS anticipated LPS phenotype): of interest, no similar case has been reported in the pertinent literature. Regarding the etiopathogenesis, we can speculate that the primitive tumor itself probably selected different cellular clones in order to recur, developing a sort of acquired resistance to the administered chemotherapy. Its future behaviour is unpredictable: considering the high frequency of local recurrences by this and other paratesticular sarcomas, we strongly recommend careful and prolonged surveillance [2-5]. In conclusion, characterizing paratesticular soft tissue tumors is not a simple task: they can show single (LPS and LMS above all) as well as multiple lines of differentiation (MM, L-LMS, DDLS, and DL-LMS). As for multilineage paratesticular sarcomas, from the literature we know of cases of LPS hosting synchronous or metachronous LMS. The occurrence of the inverse event, that is a LMS transforming into LPS in order to recur, is an unreported phenomenon which should alert oncologists to the aggressive potentiality and malignant evolution of paratesticular LMS.

Rationale: Malignant mesenchymoma (MM) is defined as a heterogeneous malignant soft tissue tumor that consists of 2 or more distinctly different mesenchymal components in addition to fibrosarcomatous elements. Bladder MM was rarely reported in the literature and there are only 5 cases of primary bladder MM documented in English literature to date. Patient concerns: A 58-year-old male complained of difficulty in urination and intermittent gross hematuria for 3 months. Doppler ultrasound scan revealed an avascular and homogeneous hypoechoic mass measured 6.5 × 9 cm in the bladder. Computed tomography showed a homogeneous solid mass in the bladder. Diagnoses: Pathology revealed spindle-shaped tumor and proliferation of poorly differentiated immature mesenchymal cells rich in eosinophilic cytoplasm with hyperchromatic sticklike nuclei. Immunohistochemical examinations were positive for CD117. Interventions: The patient was diagnosed with presence of bladder tumor and underwent radical cystectomy; the optimal treatment strategy was reviewed and discussed. Outcomes: There was no recurrence or metastasis during a 16-month follow-up. Lessons: Our case study demonstrated bladder MM with a relatively indolent clinical course. A multidisciplinary approach including surgery, radiotherapy, and chemotherapy may be useful. Radical resection is the most important determinant of clinical outcome. Generally, the clinical outcome and prognosis of mesenchymoma are favorable.

A male castrated Golden Retriever was presented for evaluation of a large mass over the left shoulder extending to the lower part of the neck that had been present for an extended period of time, but had a recent history of rapid growth. Previous aspirates of the mass were consistent with a lipoma. The mass was surgically excised and was diagnosed as an extraskeletal osteosarcoma based on histopathology. After surgery, the dog was initiated on a chemotherapy protocol with carboplatin and metronomic cyclophosphamide. He became neutropenic, anemic, and thrombocytopenic 14 days after the carboplatin treatment was administered. The neutropenia resolved, but the anemia and thrombocytopenia progressed. A bone marrow aspirate revealed erythroid hypoplasia, myeloid hyperplasia with a predominance of early precursors, and a subset of cells that made up 20% of the total population that were reported as bizarre and unclassifiable. These cells were discrete in nature and were thought to be hematopoietic in origin. The dog was euthanized due to deterioration of the clinical condition. On postmortem examination, widespread metastasis involving the lungs, liver, kidney, heart, and bone marrow was found. Histopathology of the tumor lesions determined 2 distinct malignant populations of liposarcoma and osteosarcoma, consistent with malignant mesenchymoma. However, the possibility of 2 separate neoplastic processes cannot be definitively excluded. This is the first report of bone marrow metastasis of a malignant mesenchymoma in a dog.

A 13-year-old spayed bitch was referred for evaluation of an abdominal distension with a palpable, continuously growing mass. Abdominal ultrasonography revealed a 30 × 20 cm mass directly connected to the spleen. Surgical exploration confirmed the sonographic diagnosis with adhesions to the omentum and the liver. Pathohistological samples revealed well differentiated adipose tissue and variably differentiated collagenous and myxomatous tissue. Immunohistochemically, vimentin and in some regions alpha smooth muscle actin were expressed indicating smooth muscle differentiation. The results support the diagnosis of a malignant mesenchy - moma composed of liposarcoma, mixosarcoma and leiomyosarcoma. No local recurrence or metastasis occurred during a nine month follow-up. So far, only two pathological retrospective studies describing the common preva - lence and properties of canine splenic malignant mesenchymomas were found in the literature. However, this rare tumor entity has to be considered as a differential diagnosis in cases of large splenic masses.

A captive, adult, male northern saw-whet owl (Aegolius acadicus) was examined for blepharospasm of the left eye. The owl was diagnosed with bilateral anterior uveitis and a corneal ulceration in the left eye. It was treated with oral and topical nonsteroidal anti-inflammatory medications and a topical antibiotic. Multiple recheck examinations and medication adjustments were performed over the next 4 months, at the end of which time the bilateral anterior uveitis was controlled with a topical nonsteroidal anti-inflammatory applied 3 times per week to both eyes. The owl was re-examined 2 months later after 2 suspected neurologic episodes. On physical examination, the owl was quiet and had difficulty standing and ambulating. Five firm multilobular and immobile masses were identified overlying the pectoral muscle and sternum. Fine-needle aspiration from 1 mass revealed neoplastic cells consistent with a sarcoma. The owl was euthanatized. On the basis of results of histopathologic examination, the mass was diagnosed as a pleomorphic spindle cell sarcoma with features of rhabdomyosarcoma, liposarcoma, and osteosarcoma. Numerous tumor cells were immunopositive for myoglobin and desmin, indicating striated muscle origin. Although a metastatic lesion was present in 1 adrenal gland, lesions of inflammation or neoplasia were absent in either eye on histopathologic examination. This report describes an apparent ocular manifestation of systemic disease in an avian species with clinically diagnosed recurrent anterior uveitis.

A 20-yr-old African fur seal (Arctocephalus pusillus) presented with a slowly growing mass located on the dorsum at the level of the last thoracic vertebrae. The mass was hard, 10 cm in diameter, and not adherent to the underlying tissues. Multiple biopsies were collected for histopathology and revealed extensive areas of necrosis, small nodules of malignant mesenchymal proliferation with areas of chondroid metaplasia, and atypical cells in vessel walls. The morphologic diagnosis was suggestive of malignant mesenchymal neoplasia originating from the vascular wall. The mass was removed 1 mo later due to ulceration and infection. Histologically, based on the World Health Organization's classification of neoplastic processes in domestic animals, the tumor was consistent with malignant mesenchymoma. The margins of resection revealed the presence of neoplastic cells. Based on these results, the particular species involved, the high local invasiveness, and the high metastatic index of this malignant tumor in domestic mammals and humans, the prognosis was poor. The animal died 6 mo later with metatastic disease.

Purpose. To check whether primary involvement of brain/spinal cord by bone/soft tissue sarcomas’ metastases in children is as rare as described and to present various morphological forms of bone/soft tissue sarcomas’ CNS metastases. Methods. Patients with first diagnosis in 1999–2014 treated at single center were included with whole course of disease evaluation. Brain/spinal canal magnetic resonance imaging (MRI)/computed tomography were performed in cases suspicious for CNS metastases. Extension from skull/vertebral column metastases was excluded. Results. 550 patients were included. MRI revealed CNS metastases in 19 patients (incidence 3.45%), 14 boys, aged 5–22 years. There were 12/250 osteosarcoma cases, 2/200 Ewing’s sarcoma, 1/50 chondrosarcoma, 3/49 rhabdomyosarcoma (RMS), and 1/1 malignant mesenchymoma. There were 10 single metastases and 7 cases of multiple ones; in 2 RMS cases only leptomeningeal spread in brain and spinal cord was found. Calcified metastases were found in 3 patients and hemorrhagic in 4. In one RMS patient there were numerous solid, cystic, hemorrhagic lesions and leptomeningeal spread. Conclusions. CNS metastases are rare and late in children with bone/soft tissue sarcomas, although in our material more frequent (3.45%) than in other reports (0.7%). Hematogenous spread to brain and hemorrhagic and calcified lesions dominated in osteosarcoma. Ewing sarcoma tended to metastasize to skull bones. Soft tissue sarcomas presented various morphological forms.

In accordance with recent terminology, it is proposed that malignant mesenchymoma should be renamed 'composite sarcoma' and defined as 'a sarcoma composed of two or more cellular types each of which is sufficiently differentiated to permit clear recognition of its histogenetic type microscopically, immunohistochemically or ultrastructurally; excluding fibrosarcomatous and high-grade pleomorphic undifferentiated sarcomatous component, dedifferentiated sarcoma and the combination of osteosarcoma and chondrosarcoma which is regarded as a single histogenetic type'. Four cases of primary osseous composite sarcoma (POCS) were identified among 928 primary bone sarcomas. Their age ranged from 10 to 87 years, peak incidence in the second decade with equal sex distribution. Most presented with pain, commonest in the knee, affecting the metaphysis, appearing radiologically as expansile infiltrative osteolytic lesions with cortical erosion, periosteal reaction, variable extent of osteoblastic areas and soft tissue extension. All contained variable amounts of conventional high-grade osteosarcoma with or without chondrosarcoma component; the other constituents were liposarcoma, rhabdomyosarcoma and leiomyosarcoma. In all cases, Ki67 proliferative index was over 35%, there was no CDK4 and MDM2 amplification. The absence of low-grade component supported the de novo origin of POCS rather than derivation from divergent dedifferentiation. The two older patients with hitherto undescribed osteoleiomyosarcoma died 2 and 10 months after operation, whereas the two younger with osteorhabdomyosarcoma and osteoliposarcoma enjoyed disease-free survival at 16 and 6 years after chemotherapy despite the latter showing lung metastasis at presentation. Identification of the different lines of differentiation together with their approximate amounts and histological grades is therefore mandatory for POCS as multi-agent chemotherapy catered for each sarcoma component might offer hope for long-term disease-free survival.

Malignant mesenchymoma is combined soft tissue tumors of mesenchymal origin. Cutaneous combined sarcomas are exceedingly rare. We report the case of an 81-year-old woman who presented a left cutaneous mass. She underwent a wide local excision. Histopathological and immunohistochemical studies were consistent with the diagnosis of combined pleomorphic liposarcoma and conventional osteosarcoma (malignant mesenchymoma). Although it is extremely rare, this case suggests that combined sarcoma should be considered in the differential diagnosis of undifferentiated pleomorphic neoplasms.

Malignant transformation of a uterine leiomyoma is an exceedingly rare phenomenon. Previous reported examples of malignant neoplasms to arise so include leiomyosarcoma, angiosarcoma, and malignant mesenchymoma. We report an intramural carcinosarcoma arising in a uterine leiomyoma in a 38-year-old woman. This case is unique in being the first recorded carcinosarcoma arising within a uterine leiomyoma and the first example of an epithelial neoplasm to do so. We discuss the differential diagnosis and possible pathogenesis of the tumor that has likely arisen secondary to epitheliogenesis in a mesenchymal neoplasm.

Highlights • Osseous metaplasia is an unusual presentation a breast lump. • In unusual breast lumps, a tissue biopsy should be obtained. • Osseus metaplasia of the breast can be presented as a breast lump., Introduction Benign Osseous metaplasia of the breast is rare, with only a few cases reported in the literature. Here we present a case of benign osseous metaplasia of the breast presenting as a breast lump. Case presentation 38-year-old previously well woman presented with a one-year history of bilateral breast pain and a left-sided breast lump. Ultrasound and mammography suggested calcified fibroadenoma. An ultrasound-guided true cut biopsy revealed fibrous tissue containing foci of adenosis in the presence of a myoepithelial cell layer. Excision biopsy was performed, and histopathological examination showed bone matrix deposition occupying most of the nodule with peripheral hyalinized tissue but no evidence of malignancy. A diagnosis of benign osseous metaplasia of the breast was made, and the patient recovered well without recurrence after lump excision. Discussion Only a few cases of osseous metaplasia are reported in the literature. Most reported cases are malignant, such as in fibrosarcoma, malignant mesenchymoma, osteoid sarcoma, osteogenic sarcoma, and osteochondrosarcoma.Very few cases of osseous sarcoma are reported in benign lesions such as fibroadenoma, pleomorphic adenoma, benign mesenchymoma, phyllodes tumor, and amyloid tumor of the breast. Joshi et al. first reported a case of benign osseous metaplasia of the breast presenting as breast lump in an HIV-positive patient [18]. We, therefore, consider this case to be the second case report of benign osseous metaplasia of the breast presenting as a breast lump, but the patient had no chronic illness. Conclusion A breast lump can be the first presentation of benign osseous metaplasia.

A rare case is reported of malignant mesenchymoma of a retroperitoneal lesion involving the kidney and composed of leiomyosarcoma and liposarcoma. The tumor, measuring 13 x 12 x 11 cm and weighing 1910 g, arising from the soft tissue of the retroperitoneum or renal capsule, was completely removed surgically. Thirteen months after surgical operation, multiple metastasis was observed. Immunohistochemical and electron microscopical examination showed two different mesenchymal elements. Magnetic resonance imaging findings were compatible with the pathological findings. This case appears to be the second in the world literature.

OBJECTIVE To study the clinical and histopathological characteristics of pulmonary blastoma (PB), and to review the diagnostic criterion and treatment methods. METHODS Clinical and histopathological data from 15 cases of PB in this hospital, from 1990 to 2006, were retrospectively analyzed. RESULTS Surgical procedures were conducted in all 15 patients, including pulmonary lobectomy in 9, lobectomy of the 2 right pulmonary lobes in 2, excision of pulmonary segments in 1, lobectomy and bronchoplasty in 1, lobectomy and angioplasty in 1, and excision of the whole left lung in 1. Of the 15 cases, 11 were misdiagnosed as lung cancer, 2 were doubted to be a benign tumor before surgery, 1 was suspected to be a malignant mesenchymoma, and only 1 was diagnosed as a PB. CONCLUSION Preoperative final diagnosis of PB is very dificult, since the clinical symptoms of the disease are nonspecific. To confirm the diagnosis, comprehensive consideration of the factors, such as the clinical manifestations, morphological characteristics and immunohistochemical tumor markers, should be taken. Surgery is the treatment of choice for PB, and a thorough removal is the key to a cure. PB has a high malignancy and often recurs and metastasizes, usually with a poor prognosis.

Malignant mesenchymoma is a soft-tissue tumor arising preferentially in the extremities and the retroperitoneum. We report a case of primary malignant mesenchymoma of the left side of the posterior mediastinum with local recurrence on both sides of the mediastinum. A 24-year-old woman was admitted to our hospital complaining of cough. Chest X-ray showed a giant mass in two-thirds of the left lung field, and computed tomography of the chest revealed a lobulated large mass with a fat-density area and a calcified spot in the mediastinum and left pleural space. Magnetic resonance of the chest demonstrated a large, solid mass consisting mainly of areas with the same intensity as fatty tissue and partly of areas of heterogeneous moderate intensity. The tumor was resected completely through a left posterolateral thoracotomy. The pathologic diagnosis was malignant mesenchymoma: well-differentiated liposarcoma with osteocartilagenous differentiation. The patient had local recurrence in both sides of the mediastinum 3 years and 6 months after surgery, and the recurrent tumors were completely resected again.

症例は65歳, 男性. 平成18年1月に腹部腫瘤を自覚し, 2月に近医で巨大肝腫瘍を疑われて当科に紹介された. 腹部に直径25cmの可動性不良な腫瘤を触知し, 腹部造影CT検査で肝右葉の尾側, 上行結腸の腹側に径24×16×9cmの不整形腫瘤を認め, 胆嚢, 膵, 十二指腸は圧排されていた. 腹腔内GISTあるいは脂肪肉腫を疑い3月14日手術を施行した. 腫瘍は後腹膜由来で肝S6, 横行結腸と強く癒着していたため, 腫瘍切除, 肝S6部分切除, 横行結腸切除術を行った. 術中・標本所見からは脂肪肉腫を疑ったが病理組織学的に腫瘍内に脂肪肉腫や軟骨肉腫といった多彩な肉腫成分を認め, 悪性間葉腫 (malignant mesenchymoma) と診断された.

A 12-year-old German shepherd crossbreed dog was presented with a submandibular mass that was initially diagnosed as myxosarcoma on incisional biopsy. Chest radiographs were taken for staging, and magnetic resonance imaging was performed to assess the feasibility of cytoreductive surgery before adjuvant radiotherapy. The dog underwent debulking surgery, and histology permitted reclassification of the tumour as a malignant mesenchymoma (with myxosarcomatous and osteosarcomatous differentiation). The dog was subsequently treated with four fractions of radiotherapy given at seven-day intervals and three doses of carboplatin. The dog remained stable following therapy until its condition acutely deteriorated, and it was euthanased 153 days after surgery. On postmortem examination, there were no signs of local tumour recurrence, but metastases were observed both in the thorax and in the abdomen.

Pleuropulmonary blastoma (PPB) was defined in 1988 by Manivel et al. in a series describing 11 intrathoracic pulmonary neoplasms in young children [1]. The PPB is a unique peripheral pulmonary or pleural-based tumor of childhood that is characterized in its earliest form as a bland-appearing multiloculated cyst with small foci of tumor cells and in later forms as mixed and predominantly primitive, overtly malignant neoplasms [2,3]. Prior to the introduction of the PPB as a distinct entity, this tumor had been reported in the literature as pulmonary blastoma, sarcoma arising in mesenchymal cystic hamartoma, embryonal sarcoma, malignant mesenchymoma, primary pulmonary rhabdomyosarcoma and rhabdomyosarcoma arising in congenital adenomatoid malformation or bronchogenic cyst. Over the past 15 years, PPB has come to be recognized in centers around the world. With the establishment of the Pleuropulmonary Blastoma Registry by Jack Priest, MD, and colleagues, there has been improved understanding of this rare pediatric neoplasm. The registry Web site serves as an important resource for physicians and families ( http://www.ppbregistry.org ).

Background Malignant mesenchymoma is a rare tumor and location in the uterus is even rarer. We describe the first case of malignant mesenchymoma arising from a uterine fibroid in the menopause. Case report A 64-year-old woman presented with abdominal pain and underwent surgery for a large "uterine fibroid" with suspicious features on ultrasound scan. The mass had developed after the menopause. Histology showed benign leiomyomatous tissue with malignant areas consistent with malignant mesenchymoma. Conclusion We report the first case of malignant mesenchymoma arising from the uterus in menopause. Certain radiological features may be associated with this tumor. Due to its rarity, information on management of uterine malignant mesenchymoma is lacking and management options of uterine leiomyosarcomas are reviewed as a surrogate.

Malignant mesenchymoma, defined by Stout as sarcomas comprising two or more unrelated differentiated tissue elements other than a fibrosarcoma component, is rare. We report a case of primary malignant mesenchymoma of the proximal fibula in a 10-year-old female student who presented with pain and swelling of the right knee for 2 months. Initial biopsy showed features of rhabdomyosarcoma only, but the resected specimen revealed additional osteosarcomatous and chondrosarcomatous elements. The patient remained well more than 5 years after initial presentation. Including our present patient, 16 cases of primary malignant mesenchymoma of bone are found in the English literature, affecting mainly adolescents and young adults, with a slight male predominance and predilection for the metaphysis of long bones, especially around the knee. More than 60% of the patients develop metastasis, almost invariably to the lung, but occasionally to the brain. About 60% of the patients, all with metastasis, died mostly within one year of diagnosis. The clinical features of primary malignant mesenchymoma of bone thus resemble those of conventional osteosarcoma. Moreover, our case illustrates that, with combination chemotherapy targeted for individual elements, the prognosis of this rare tumour might be much improved, as in osteosarcoma.

This focused review is designed to summarize state-of-the-art management for patients with localized soft tissue sarcomas of the extremities. The revised staging system of the International Union Against Cancer/American Joint Committee on Cancer (AJCC) for this disease is described, along with recommendations for the diagnostic workup. Brief summaries of the roles of surgical therapy, pre- and postoperative radiotherapy, and pre- and postoperative chemotherapy in the management of extremity soft tissue sarcoma are provided. Staging The relative rarity of soft tissue sarcomas, the anatomic heterogeneity of these lesions, and the presence of more than 30 recognized histologic subtypes of variable grade have made it difficult to establish a functional system that can accurately stage all forms of soft tissue sarcoma. Currently, the most widely employed staging system for sarcoma is the sixth edition of the American Joint Committee on Cancer (AJCC) staging system [1]. The modifications to the previous version of the AJCC system include reclassifying T2b, G1-2, N0, and M0 lesions as stage I rather than stage II lesions. The sixth edition AJCC staging system applies to all soft tissue sarcoma subtypes, except angiosarcoma, malignant mesenchymoma, grade 1 fibrosarcoma (desmoid tumor), and dermatofibrosarcoma protuberans. Histologic grade and tumor size are the primary determinants of AJCC stage (Table 1). Tumor size is subcategorized as ‘‘a’’ (superficial tumor arising outside the investing fascia) or ‘‘b’’ (a deep tumor that arises beneath the

Extraskeletal osteosarcoma (EOS) is rare and commonly arises in the retroperitoneum, limbs, head and neck. There is no significant difference between EOS and other malignant tumors in soft tissue. Localized pain and swelling are the common presenting symptoms. Clinical diagnosis of EOS is difficult, imaging techniques may be helpful and careful, and the histopathological analysis is necessary. The common histological variants of EOS include: osteoblastoma, chondroblastoma, and fibroblastoma, and other unusual subtypes were reported occasionally. It should be distinguished with myositis ossificans, malignant mesenchymoma, giant cell tumor and parosteal osteosarcoma. We present an EOS arising in the penis. The primary site and histological category of the tumor were extremely rare. We hope the case will be helpful to the recognition of clinical signs, iconography and histopathology of EOS.

Malignant ectomesenchymoma is a rare soft tissue tumor of childhood composed of both mesenchymal and neuroectodermal elements. Reported sites of origin are head and neck, abdomen, perineum, scrotum, and extremities. A new case of an orbital ectomesenchymoma in a 7-year-old boy is presented. The clinical picture of the tumor, radiological findings, and its histopathologic and immunohistochemical characteristics are described. The patient was successfully treated with combined surgical resection and chemotherapy. All the other reported cases of malignant ectomesenchymoma with various sites of origin are also reviewed.

Malignant mesenchymoma of the uterus, arising in a leiomyoma Aims: To document and find evidence for the rare occurrence of malignant progression of a benign uterine leiomyoma with divergent mesenchymal differentiation. In a 54-year-old female a large pedunculated tumour was encountered which had suddenly increased in size and had apparently arisen at the site of a subserosal uterine leiomyoma first described 19 years earlier. The tumour seemed histologically diverse in its composition. The possibility of malignant progression of the benign leiomyoma with divergent mesenchymal differentiation was entertained. Methods and results: In the resected tumour, smooth muscle, osseous and adipose components were identified and these were assessed using recognized histological criteria of malignancy. In addition to a benign smooth muscle component, malignant leiomyosarcomatous tissue was seen in addition to a malignant osseous component and a malignant adipose component. The tumour thus met the criteria of a malignant mesenchymoma. The relationship of the different components of the tumour was analysed by immunohistochemistry and with molecular loss of heterozygosity (LOH) analysis. In the osseous and leiomyosarcomatous components a similar LOH pattern was observed. The adipose component showed a distinct LOH pattern. Retention of smooth muscle differentiation in the osseous component was demonstrated by desmin immunostaining. Conclusion: Malignant transformation of benign uterine leiomyoma may rarely occur. Mesenchymal stem cells underlying these tumours may show divergent mesenchymal differentiation.

悪性間葉腫は線維肉腫を除く, 2種類以上の肉腫成分から構成される稀な悪性腫瘍で,主として四肢や体幹に発生する.臨床上は未熟奇形腫や中胚葉性混合腫瘍との鑑別が重要である.今回,再発を繰り返した後腹膜悪性間葉腫の1例を経験したので報告する.症例は73歳,女性で,主訴は左季肋部痛,体重減少.腹部CTでは,左腎や腹部大動脈を圧排する12cm×8.5cmの不均一で一部に粗大石灰化を有する後腹膜腫瘍であった.手術では腫瘍は周囲臓器に浸潤なく一塊として容易に切除できた.病理組織学的検査により軟骨肉腫と平滑筋肉腫からなる悪性間葉腫と診断された.術後は2度の再発をきたし,いずれも発生部位が異なった.予後不良と考えられる.

Undifferentiated embryonal sarcoma (UES) is a rare and highly malignant hepatic neoplasm, affecting almost exclusively the pediatric population. It has replaced malignant mesenchymoma, under which diagnostic term the first three cases were described. A link between embryonal sarcoma and mesenchymal hamartoma of the liver (MHL) has long been proposed, because of clinicopathologic overlaps of these entities; however, until recently, this association remained tenuous. Cases of UES arising in a background of mesenchymal hamartoma of the liver have previously been reported in two teenage girls. Discovery of a similar genetic abnormality in MHL and UES has clinched the supposed link between them. There have also been two reports of UES with prominent cystification, one associated with peripheral eosinophilia, and thereby masquerading as hydatid cyst of the liver. We report a case of UES arising in a young boy with MHL, with unusual histologic features, including large mesothelial-lined cysts and ectopic adrenal cortical tissue under Glisson's capsule.