Sarcomatoid neoplasms of the lung and pleura

Sarcomatoid neoplasms of the lung and pleura are rare tumors that present a complex differential diagnosis, making them challenging for surgical pathologists. In the lung, the main tumors are the sarcomatoid carcinomas, including pleomorphic carcinoma, spindle cell carcinoma, giant cell carcinoma, carcinosarcoma, and pulmonary blastoma. They are characterized by histologic heterogeneity; molecular data support their origin from a pluripotent stem cell that undergoes neoplastic transformation with divergent epithelial and sarcomatous differentiation. Diagnosis is difficult in small biopsy specimens and typically requires a resection specimen. Despite the presence of sarcomatoid features, these tumors are classified as lung carcinomas. Pulmonary blastomas must be distinguished from pleuropulmonary blastomas, which are a unique type of thoracic sarcoma typically occurring in young children. In the pleura, the main tumors to consider are the sarcomatoid and desmoplastic types of malignant mesothelioma, solitary fibrous tumor, and desmoid tumor. While light microscopy is sufficient to diagnose most of these tumors, immunohistochemistry can be useful in selected settings. In particular, it can aid to confirm epithelial differentiation in spindle cell carcinomas and the presence of rhabdomyosarcoma in sarcomatoid carcinomas, mesotheliomas, or pleuropulmonary blastomas. For sarcomatoid and desmoplastic mesothelioma, keratin is the most useful stain because it can highlight invasive growth and mesothelial markers are positive in only the minority of cases. Clinical and radiologic correlation is needed to separate some pleomorphic carcinomas with pleural involvement from sarcomatoid malignant mesothelioma, since these poorly differentiated tumors may not express the usual immunohistochemical markers for carcinoma or mesothelioma.     

Spindle basaloid squamous carcinoma of the upper aerodigestive tract: immunohistochemical and clinicopathological study of three cases

We describe the clinicopathological and immunohistochemical features of three spindle (sarcomatoid) basaloid squamous carcinomas in three men aged 73, 69, and 59 years with a history of tobacco and alcohol abuse. Two tumors were located in the hypopharynx and one was located in the nasal cavity. The three tumors have a pedunculated polypoid appearance. Histologically, they were composed of conventional basaloid squamous carcinomas with extensive malignant spindle cell proliferation, comprising more than 50% of the tumor. The sarcomatoid component demonstrated immunoreactivity with one or more epithelial markers. One case in addition expressed CD99 and Bcl-2 and was originally diagnosed as monophasic synovial sarcoma; however, a subsequent biopsy disclosed basaloid squamous cell carcinoma with sarcomatoid stroma. Two patients were treated with surgery and radiation whereas one refused therapy. The patients were alive 14 (case patient 1), 10 (case patient 2), and 8 (case patient 3) months after diagnosis. In the absence of evidence from immunohistochemical or electron microscopy studies, a polypoid malignant spindle cell tumor of a mucosal surface of the upper aerodigestive tract should be considered a sarcomatoid carcinoma until proven otherwise. The type of epithelial component would determine the subtype of sarcomatoid carcinoma.     

Sarcomatoid carcinoma of the urinary bladder: a clinicopathologic and immunohistochemical analysis of 14 patients

Sarcomatoid carcinoma of the urinary bladder is a rare entity, in which both the histogenesis and biological behavior remain controversial. We herein describe the clinicopathologic and immunohistochemical profiles of sarcomatoid carcinomas and discuss the significance of cell adhesion molecules in the development of this peculiar neoplasm. The authors examined formalin-fixed and paraffin-embedded tissue samples from 14 patients with sarcomatoid carcinoma of the urinary bladder. An immunohistochemical analysis was performed by using antibodies against epithelial and mesenchymal antigens as well as adhesion molecules. Most patients suffered from an advanced stage of the tumor, extending to the muscular layer (7 cases) or to the perivesical tissues (5 cases). Microscopically, all 14 tumors were composed predominantly of a carcomatoid component and an obviously carcinomatous component. The sarcomatoid component was composed of a mixture of spindle cells, round cells, and pleomorphic giant cells. The carcinomatous components consisted of papillary or nonpapillary high-grade transitional cell carcinoma (TCC). The zones of gradual transition between the carcinomatous and the sarcomatous elements were focally apparent in each tumor. The findings of an immunohistochemical examination indicated that both carcinomatous and sarcomatoid components expressed epithelial antigens (pankeratin or EMA), even though the staining pattern varied from case to case. As for cell adhesion molecules, the carcinomatous components were positive for E-cadherin (8 of 12), CD44s (8 of 12), and CD44v6 (6 of 12). Although the sarcomatoid components were also positive for E-cadherin (5 of 12), CD44s (4 of 12), and CD44v6 (3 of 12), these rates were lower than those in the carcinomatous components. Six patients died of their disease between 5 and 36 months after the diagnosis was made. The recognition of sarcomatoid carcinomas has important therapeutic and prognostic implications. It seems appropriate to treat these neoplasms in the same manner as conventional high-grade TCCs with similar degrees of invasion. We consider that sarcomatoid carcinomas should be regarded as a high-grade carcinoma that shows a prominent pseudosarcomatous dedifferentiation. The sarcomatoid component of sarcomatoid carcinomas may result from either anaplastic changes or dedifferentiation related to the process of losing cell adhesion molecules.     

Renal mucinous tubular and spindle carcinoma lacks the gains of chromosomes 7 and 17 and losses of chromosome Y that are prevalent in papillary renal cell carcinoma.

Mucinous tubular and spindle cell carcinoma of the kidney is an uncommon, distinctive neoplasm characterized by the proliferation of cuboidal and spindle cells arranged in tubular or sheet-like arrays, typically with a mucinous or myxoid background. The most important differential diagnostic consideration of mucinous tubular and spindle cell carcinoma is papillary renal cell carcinoma, type 1, with sarcomatoid transformation. The aim of our study is to investigate the pattern of possible gains or losses of chromosomes 7, 17 and Y in 10 mucinous tubular and spindle cell carcinomas with interphase fluorescence in situ hybridization (FISH). Four-micron sections were obtained from paraffin blocks representative of the tumors and including adjacent non-neoplastic renal parenchyma from 10 patients. The patients' ages ranged from 20 to 80 years (mean: 62 years); eight were female, while two were male. FISH analysis was performed with centromeric probes for chromosomes 7, 17 and Y. One hundred fifty to 200 nuclei from each case were scored for hybridization signals and non-neoplastic parenchyma served as control tissue. We found that renal mucinous tubular and spindle carcinoma lacks the gains of chromosomes 7 and 17 and losses of chromosome Y that are typical of papillary renal cell carcinoma. FISH analysis with centromeric probes for these chromosomes is potentially helpful in differentiating mucinous tubular and spindle cell carcinomas from papillary renal cell carcinomas.     

Unusual forms of carcinoma of the urinary bladder.

Carcinomas of the urinary bladder, which differ histologically from the usual transitional cell carcinoma of the bladder, are reviewed. These tumors, which account for approximately 15% of all bladder carcinomas, have diverse microscopic appearances. They fall into four major categories: variant forms of urothelial (transitional cell) carcinoma, squamous cell carcinoma, adenocarcinoma, and undifferentiated carcinoma. In the first category, the most common are carcinomas with glandular or squamous differentiation. Less common, but more troublesome diagnostically, are variants in which the cells are spindle shaped (sarcomatoid carcinoma), form small cysts (microcystic carcinoma), or differentiate toward trophoblast. In other variants, the stroma has unusual features that may lead to diagnostic difficulty. These are carcinomas with pseudosarcomatous stroma, osseous or cartilaginous metaplasia, or osteoclast-type giant cells. Also reviewed are squamous cell carcinoma and its variant, verrucous carcinoma. Vesical adenocarcinoma has several variants, including signet-ring cell and clear cell types. Finally, the category of undifferentiated carcinoma, including small cell carcinoma, giant cell carcinoma, and lymphoepithelioma-like carcinoma, is discussed.     

Transitional cell carcinoma of the urinary bladder with pseudosarcomatous stroma

An 84-year-old man who complained of hematuria had transurethral resection of a large polypoid tumor in the urinary bladder. Pathologic examination showed an invasive, moderately differentiated transitional cell carcinoma with numerous atypical mesenchymal cells in its stroma. The latter cells failed to stain immunohistochemically for epithelial markers and were interpreted as reactive or pseudosarcomatous in nature. Transitional cell carcinomas with pseudosarcomatous stroma should be distinguished from bladder tumors with a neoplastic spindle cell component such as sarcomatoid carcinomas and carcinosarcomas.     

Pseudosarcomatous and sarcomatous proliferations of the bladder

Pseudosarcomatous fibromyxoid tumor (PFT), postoperative spindle cell nodule (PSN), sarcoma, and sarcomatoid carcinoma of the bladder are frequently difficult to distinguish histopathologically with significant differences in disease-related outcomes. A retrospective review of our pathology registry over the last 25 years identified 7 PFT, 10 PSN, 18 primary bladder sarcomas, and 17 sarcomatoid carcinomas. Most patients with PFT, PSN, sarcoma, and sarcomatoid carcinoma were diagnosed between the ages of 50 to 60 years with PFT and PSN most commonly detected in women. A previous history of urological instrumentation and bladder cancer was present in all patients with PSN but none of the patients with PFT. Pseudosarcomatous fibromyxoid tumors were characterized by a tissue culture-like proliferation of myofibroblastic cells with focal atypia and overall cytoarchitectural features mimicking nodular fasciitis. Sarcomas and sarcomatoid carcinomas exhibited cellular atypia, mitotic activity with atypical mitosis, and the presence of necrosis. Transurethral resection was sufficient to control all PFT and PSN with no evidence of distant metastatic spread. In contrast, local recurrences and distant metastases frequently occurred in patients with primary sarcoma and sarcomatoid carcinoma despite aggressive surgical management, which was often combined with neoadjuvant chemotherapy (50% and 65% disease-specific mortality, respectively). Pseudosarcomatous fibromyxoid tumor and PSN have unique clinical and pathologic features that allow their distinction from primary bladder sarcoma and sarcomatoid carcinoma.     

Immunohistochemical demonstration of human chorionic gonadotropin in tumors of the urinary bladder

All transitional cell carcinomas of the bladder diagnosed in male patients within a five year period were studied for human chorionic gonadotropin (hCG) production. Biotin-avidin immunoperoxidase analysis for hCG was performed on all paraffin blocks containing carcinoma-in-situ, grade I, grade II, and grade III transitional cell carcinoma. Of a total of 29 patients, one case of carcinoma-in-situ (1/5), and five cases of grade III transitional cell carcinoma (5/15) were found to have hCG-positive tumor cells. The findings indicate that transitional cell carcinoma should be added to the list of malignant tumors capable of producing hCG.     

Anaplastic and sarcomatoid carcinoma of the small intestine: a clinicopathologic study

Carcinomas involving the jejunum and ileum are rare tumors. During a review of small intestinal neoplasms, six primary carcinomas of jejunum or ileum with an anaplastic and sarcomatoid histology were identified. At presentation, three of the patients had symptoms related to metastatic disease and three had symptoms referable to the local tumor. The tumors were large (greater than 4.5 cm in diameter), usually endophytic masses composed of large cells with eosinophilic cytoplasm, anaplastic nuclei, and prominent nucleoli. In many areas, the cells had a spindled configuration. Mucin positivity was identified in all six cases. Electron microscopic findings in two cases were indicative of epithelial differentiation. The tumors behaved aggressively; all five patients for whom there was clinical follow-up died of metastases within 40 months. The six anaplastic and sarcomatoid carcinomas were compared with 29 typical adenocarcinomas arising in the jejunum or ileum. Only two of the latter group had symptoms referable to distant metastases at presentation. These tumors also tended to be smaller at presentation (11 tumors were less than 4 cm in greatest dimension). Of 25 patients with typical adenocarcinomas who had acceptable follow-up, 18 (72%) died of disease and five (20%) were alive with no evidence of disease after 5 years. We conclude that anaplastic and sarcomatoid carcinoma is a rare variant of small intestinal carcinoma with an aggressive clinical course.     

Low-grade metaplastic carcinomas of the thymus: biphasic thymic epithelial tumors with mesenchymal metaplasia--an update.

A group of biphasic low-grade thymic epithelial tumors is presented that we suggest calling low-grade metaplastic carcinoma of the thymus [37]. Four of the patients were men, their age ranging from 44 to 71 years. Three tumors invaded mediastinal fat or pleura. No metastases were present. Histologically, the tumors showed a biphasic pattern with solid carcinomatous areas merging with a spindle cell component. Only few lymphocytes were present. Cytological atypia and mitotic activity were variable in the solid areas, but low in the spindle cell component. The tumors showed expression of cytokeratin, vimentin and/or epithelial membrane antigen (EMA), both in the carcinomatous and in spindle cell components. In two cases, actin expression was also present in both components. In one case, chromogranin, S100 protein, glial fibrillary acidic protein, and neuron specific enolase were expressed in a minority of cells of both components. None of the patients had myasthenia gravis. All patients are alive without distant metastasis, but meanwhile one patient suffers from local recurrence. We conclude that metaplastic carcinoma of the thymus is a clinicopathological entity that is probably distinct from the recently described "thymoma with pseudosarcomatous stroma", and should be distinguished from the usually benign medullary thymomas and the highly aggressive carcinosarcomas and sarcomatoid carcinomas.     

Sarcomatoid carcinoma after radiation treatment of prostatic adenocarcinoma

We report 2 patients with conventional prostatic adenocarcinoma who developed sarcomatoid carcinoma of probable prostatic origin 6 and 2.5 years after radiation treatment (seed implantation and external beam). Our cases had histologic features consistent with those cases previously reported in the literature. The tumors consisted of spindle cells with large hyperchromatic nuclei and a pattern mimicking a sarcoma. Immunohistochemical studies showed the tumors to be weakly positive for EMA, CK7, and vimentin. Ki67 staining showed positivity in more than 50% of tumor cells. The tumors also stained diffusely positive for p53 and p63. PSA and PAP were negative. Clinically, the sarcomatoid carcinomas appeared to be of prostatic origin. The pathogenesis of the tumors is still uncertain but most likely represent a radiation-induced dedifferentiation of prostatic adenocarcinoma.     

Pleomorphic carcinoma of the lung expressing podoplanin and calretinin

Pleomorphic carcinoma (PC) of the lung is classified as a subtype of sarcomatoid carcinoma of the lung, and peripheral PC is sometimes difficult to differentiate from the sarcomatoid component of mesothelioma. An 80‐year‐old man was referred to National Cancer Center Hospital East because a chest X‐ray showed an abnormal shadow. CT scans of the chest indicated two solid masses located in the right lower lobe, and CT‐guided needle biopsy yielded spindle‐shaped tumor cells that were immunoreactive for both podoplanin and calretinin. Mesothelioma could not be ruled out, and the tumors were surgically resected to facilitate definitive pathological diagnosis. Both tumors were composed of undifferentiated carcinoma, bronchioloalveolar carcinoma and spindle cell carcinoma, and spindle cell component was immunoreactive for podoplanin and calretinin. Ten other tumors diagnosed as peripheral PC were also tested for podoplanin and calretinin expression. The sarcomatoid component in four of the 11 cases (36%) was immunoreactive with podoplanin, and it was calretinin positive in nine of the 11 cases (82%). When making the differential diagnosis between PC and the sarcomatoid component of mesothelioma, care is required in diagnosing biopsy specimens of peripheral lung spindle‐cell tumors that are positive for both podoplanin and calretinin.     

Chromosomal gains in the sarcomatoid transformation of chromophobe renal cell carcinoma.

The hallmark of chromophobe renal cell carcinoma is multiple chromosomal losses from among chromosomes 1, 2, 6, 10 and 17. Chromophobe renal cell carcinoma with distant metastases or sarcomatoid transformation are uncommon and little is known about their chromosomal abnormalities. We collected six sarcomatoid chromophobe renal cell carcinomas and three primary chromophobe renal cell carcinomas with distant metastases. A cytogenetic analysis by fluorescent in situ hybridization on paraffin-embedded tissue was performed using centromeric probes for chromosomes 1, 2, 6, 10 and 17. We found more than one signal in four of six (66%) sarcomatoid chromophobe renal cell carcinomas, in both sarcomatoid and adjacent epithelial components. Both primary chromophobe renal cell carcinomas and matched metastases showed single signals for all chromosomes studied in two cases and no abnormalities in the remaining case. We concluded that: (1) both epithelial and sarcomatoid components of sarcomatoid chromophobe renal cell carcinoma show different genetic abnormalities from those characteristic of chromophobe renal cell carcinoma; (2) sarcomatoid chromophobe renal cell carcinomas frequently have multiple gains (polysomy) of chromosomes 1, 2, 6, 10 and 17; (3) distant metastases show the same genetic patterns, usually chromosomal losses (monosomy), found in the primary tumors.     

Metaplastic breast carcinoma: a retrospective study of 26 cases

Metaplastic breast carcinoma is a rare invasive breast cancer. Metaplastic breast carcinoma is mainly characterized by an epithelial or mesenchymal cell population mixed with adenocarcinoma. We collected 26 cases of metaplastic breast carcinoma in the First Affiliated Hospital of Bengbu Medical College from 2008 to 2014. Tumor size, tumor grade, vascular invasion, ER/PR status, histologic classification, and HER2/neu status were assessed for all cases and the literature was reviewed. Clinicopathologic characteristics of patients diagnosed with metaplastic breast carcinomas and its key points of differential diagnosis were discussed. All patients were female, with the median age of 50 years. The mean tumor size was 3.2 cm. 4 subtypes of metaplastic breast carcinomas were documented. Fibromatosis-like metaplastic carcinomas are typically characterized by wavy, intertwined, gentle spindle cells. When the tumor components are almost squamous cell carcinoma components and the primary squamous cell carcinoma of other organs and tissues are excluded, we can diagnose breast squamous cell carcinoma. In spindle cell carcinoma, atypical spindle cells are arranged in many ways and are usually accompanied by inflammatory cell infiltrate. Cancer with interstitial differentiation has mixed malignant epithelial and mesenchymal differentiation, and the mesenchymal components are diverse. Most tumors are triple negative. At present, surgical resection combined with chemotherapy or radiation therapy is the most effective and acceptable method for treating metaplastic breast carcinoma.     

Fine-needle aspiration cytology of metaplastic carcinoma of the breast

BACKGROUND: Metaplastic carcinoma of the breast encompasses a heterogeneous group of tumours with variable components of sarcomatoid, squamous or poorly differentiated carcinomas. AIM: To review a series of 19 cytological preparations of metaplastic carcinomas to assess diagnostic cytological features. METHODS: 17 cases of fine-needle aspirates of histologically proven metaplastic carcinomas (4 monophasic spindle cell carcinomas, 4 squamous cell carcinomas and 11 biphasic tumours) were reviewed, with an emphasis on the presence of poorly differentiated carcinoma, squamous cell carcinoma, atypical spindle cells, benign stromal fragments and necrosis. RESULTS: All cases were diagnosed as malignant, with 68% of cases showing moderate to high cellularity, and 47% showing necrosis. If the tumours were analysed according to the constituting components histologically, 7, 15 and 8 cases, respectively, possess poorly differentiated carcinoma cells, sarcomatoid malignant cells and squamous carcinoma cells, whereas these components were cytologically identified in 11, 10 and 7 cases, respectively. Dual tumour populations were identified in only 5 of the 11 biphasic carcinomas in the cytological preparations; and the stromal material was cytologically identified in the only case with chondroid stroma. CONCLUSIONS: Identification of metaplastic carcinoma in cytology remains problematic. There seems to be morphological overlap between various components. The identification of dual components, unequivocal squamous carcinoma cells and chondroid stroma is helpful for diagnosis, but it is uncommon. The presence of poorly differentiated carcinoma cells with a suggestion of focal spindle morphology is another clue to the suggestion of metaplastic carcinoma.     

The evolution of collagen expression in sarcomatoid renal cell carcinoma

The development of a sarcomatoid morphotype is recognized as an extreme form of dedifferentiation in renal cell carcinoma and is associated with a poor prognosis. Although sarcomatoid renal cell carcinoma shows pronounced spindle cell morphology, clear cell renal cell carcinoma may show early spindle cell change with cellular elongation, and the prognostic significance of this is debated. To determine the relationship between sarcomatoid renal cell carcinoma and clear cell renal cell carcinoma showing early spindle cell change, we have investigated collagen expression using immunohistochemistry in these 2 tumor types. Both sarcomatoid renal cell carcinoma and early spindle cell change tumors showed pericellular interstitial expression of collagen types I and III, whereas sarcomatoid renal cell carcinoma also showed cytoplasmic expression of these collagen types. Expression of these collagen types in typical clear cell renal cell carcinoma was, in occasional cases, limited to faint and patchy staining in a pericellular interstitial distribution. Tumor cells did not stain for collagen type IV in sarcomatoid renal cell carcinoma, early spindle cell change, or typical clear cell renal cell carcinoma. In sarcomatoid renal cell carcinoma, there was diffuse pericellular expression of collagen type V and patchy pericellular expression of collagen type VI, whereas early spindle cell change tumors showed patchy pericellular staining with antibodies to collagen type V. Collagen type VI expression in early spindle cell change was largely confined to the vascular adventitia and areas of scarring, although very occasional foci of faint interstitial staining were also seen. In typical clear cell renal cell carcinoma, staining of collagen types V and VI was limited to the vascular adventitia and foci of desmoplasia, whereas no staining of tumor cell cytoplasm were seen. This study has shown that collagen expression of sarcomatoid renal cell carcinoma differs from that of early spindle cell change and provides validating evidence that these 2 morphotypes should not be considered together for classification purposes.     

Pulmonary carcinomas with a sarcomatoid element: an immunocytochemical and ultrastructural analysis

Eight primary carcinomas of the lung with a prominent spindle-cell sarcomatoid component were studied by immunocytochemical staining and electron microscopy. The eight tumors were indistinguishable by conventional light microscopy, with the exception of one unusual neoplasm that followed multiple pathways of differentiation with elements of squamous cell carcinoma, rhabdomyosarcoma, chondrosarcoma, and an undifferentiated spindle-cell population. Reticulin fiber production by individual spindle cells and a sharp demarcation of the carcinomatous and sarcomatoid domains by light microscopy were not useful differentiating features. Three of the eight tumors exhibited keratin expression in both the carcinomatous and spindle-cell components. Both immunocytochemical and electron microscopic analyses were required to detect epithelial differentiation, as in one case keratin was identified only by immunocytochemical staining and in another only by ultrastructural examination. Epithelial differentiation was undetectable in the sarcomatoid component of five tumors, and in one case immunoreactive myoglobin was identified in spindle cells; skeletal muscle differentiation was confirmed ultrastructurally. We propose that pulmonary carcinomas exhibiting evidence of epithelial differentiation in a sarcomatoid component be termed spindle-cell carcinomas and that those biphasic tumors exhibiting mesenchymal differentiation into specific tissues, such as neoplastic bone, cartilage, or striated muscle, or lacking epithelial differentiation by light microscopy, immunocytochemistry, and electron microscopy be classified as carcinosarcomas. This distinction may ultimately be unnecessary, because these two tumors may represent different points along a morphologic and biologic continuum.     

Sarcomatoid carcinoma of the urinary tract

Sarcomatoid carcinoma is a rare variant of malignant tumor arising from the urinary tract. This tumor had been termed carcinosarcoma because of its carcinomatous and sarcomatous components. There is still some confusion in the terminology between true carcinosarcoma and sarcomatoid carcinoma; however, the latter is now regarded as primarily a malignant epithelial tumor with pseudosarcomatous transformation.
Four cases of sarcomatoid carcinoma arising from the urinary tract are reported. The patients were a 77 year old female, and three males aged 62, 69 and 80 years. All but the eldest patient complained of gross hematurla. Surgical removal was performed in the younger three cases, and an autopsy was done in the remaining case. All the tumors were macroscopically polypoid. Histopathologic examination revealed fasciculated spindle-cell tumors with myxold stroma or malignant fibrous histiocytoma-like spindle cell tumors. The epithelial nature was proven in these sarcomatous cells by immunohistochemical andlor electron-microscopic examinations. Only a small amount of squamous cell carcinoma components was also evident in the latter three cases. Although the younger three patients were alive at 44, 23 and 39 months'follow-up, respectively, constant careful monitoring Is recommended.     

乳腺肉瘤样癌

观察乳腺肉瘤样癌的病理形态学特点,分型,并分析其与某些肿瘤的鉴别诊断。方法１５３８例乳腺恶性肿瘤中１５例（０．９８％）诊断为乳腺肉瘤样癌,行ＡＥ１／ＡＥ３、上皮膜抗原（ＥＭＡ）、波形蛋白、Ｓ－１００蛋白、肌动蛋白、雌激素受体（ＥＲ）和孕激素受体（ＰＲ）ＳＰ法免疫组织化学染色。另有６例是外院会诊病例,共２１例。结果按其肉瘤样成分的特点分为４个形态学类型：（１）多形肉瘤型：肉瘤样成分为多形肉瘤样。（２