An immunohistochemical study of differentiation in malignant fibrous histiocytoma

Dedifferentiated Chondrosarcoma from Molecular Pathology to Current Treatment and Clinical Trials

Dedifferentiated chondrosarcoma (DDCS) is a rare subtype of chondrosarcoma, a primary cartilaginous malignant neoplasm. It accounts for up to 1-2% of all chondrosarcomas and is generally associated with one of the poorest prognoses among all chondrosarcomas with the highest risk of metastasis. The 5-year survival rates range from 7% to 24%. DDCS may develop at any age, but the average presentation age is over 50. The most common locations are the femur, pelvis humerus, scapula, rib, and tibia. The standard treatment for localised disease is surgical resection. Most patients are diagnosed in unresectable and advanced stages, and chemotherapy for localised and metastatic dedifferentiated DDCS follows protocols used for osteosarcoma.

Undifferentiated and dedifferentiated soft tissue neoplasms: Immunohistochemical surrogates for differential diagnosis

Undifferentiated soft tissue sarcomas (USTS) are described in the current World Health Organization Classification of Soft Tissue and Bone Tumours as those showing no identifiable line of differentiation when analyzed by presently available technologies. This is a markedly heterogeneous group, and the diagnosis of USTS remains one of exclusion. USTS can be divided into four morphologic subgroups: pleomorphic, spindle cell, round cell and epithelioid undifferentiated sarcomas, with this combined group accounting for up to 20% of all soft tissue sarcomas. As molecular advances enable the stratification of emerging genetic subsets within USTS, particularly within undifferentiated round cell sarcomas, other groups, particularly the category of undifferentiated pleomorphic sarcomas (UPS), still remain difficult to substratify and represent heterogeneous collections of neoplasms often representing the common morphologic endpoints of a variety of malignant tumors of various (mesenchymal and non-mesenchymal) lineages. However, recent molecular developments have also enabled the identification and correct classification of many tumors from various lines of differentiation that would previously have been bracketed under 'UPS'. This includes pleomorphic neoplasms and dedifferentiated neoplasms (the latter typically manifesting with an undifferentiated pleomorphic morphology) of mesenchymal (e.g. solitary fibrous tumor and gastrointestinal stromal tumor) and non-mesenchymal (e.g. melanoma and carcinoma) origin. The precise categorization of 'pleomorphic' or 'undifferentiated' neoplasms is critical for prognostication, as, for example, dedifferentiated liposarcoma typically behaves less aggressively than other pleomorphic sarcomas, and for management, including the potential for targeted therapies based on underlying recurrent molecular features. In this review we focus on undifferentiated and dedifferentiated pleomorphic and spindle cell neoplasms, summarizing their key genetic, morphologic and immunophenotypic features in the routine diagnostic setting, and the use of immunohistochemistry in their principal differential diagnosis, and highlight new developments and entities in the group of undifferentiated and dedifferentiated soft tissue sarcomas.

Hematolymphoid Neoplasms Rarely Mimic Undifferentiated Pleomorphic Sarcoma of Soft Tissue

CONTEXT.—

Undifferentiated pleomorphic sarcoma (UPS) of soft tissue is defined as a sarcoma with no recognizable line of differentiation. During the past few decades, advances in ancillary studies and review of prior UPS diagnoses have narrowed the category of UPS by excluding more-specific malignancies. However, few of those studies have specifically targeted pleomorphic hematolymphoid neoplasms.

OBJECTIVE.—

To determine what fraction of UPS cases are misclassified pleomorphic hematolymphoid neoplasms, such as anaplastic large cell lymphoma, diffuse large B-cell lymphoma, histiocytic sarcoma (HS), myeloid sarcoma, and follicular dendritic cell sarcoma.

DESIGN.—

Sixty-one UPS cases were screened by tissue microarray and an immunostain panel with subsequent analysis on whole block sections for suspicious cases.

RESULTS.—

Five of 61 tumors (8%) were suggestive of HS based on the screening panel and were further evaluated with additional immunostains (PU.1, CD45, CD163) using whole sections. The 5 candidate HS cases were only focally positive for at most one stain with most staining in smaller, less-pleomorphic cells. Ultimately, no UPS met criteria for anaplastic large cell lymphoma, diffuse large B-cell lymphoma, myeloid sarcoma, follicular dendritic cell sarcoma, or HS.

CONCLUSIONS.—

Our results suggest that a UPS of somatic soft tissue is unlikely to represent a misclassified hematopoietic malignancy. Exclusion of HS is most challenging, but immunostaining for PU.1, a nuclear transcription factor, may be easier to interpret in this context.

Treatment of spinal malignant fibrous histiocytoma, a case report and literature review

OBJECTIVE

To present a case of spinal malignant fibrous histiocytoma in the fourth lumbar vertebra that received treatment by an L4 spondylectomy and placement of intervertebral expander and posterior fixation.

CASE REPORT

A 47-year-old male patient with no relevant history presented with lumbar pain of 2 months' evolution. Treated conservatively, with slight improvement in pain, the patient persisted with low back pain irradiation to pelvic members, predominantly left-sided, accompanied by weakness and claudication. Clinically, he presented with paresthesias 3/5, hypoaesthesia L4, L5 and S1, predominantly left-sided. Lumbosacral computerized axial tomography evidence of an osteolytic lesion in the L4 body, predominantly left-sided, with invasion of the lumbar canal with poorly delimited margins; lumbosacral spine MRI showed hyperintense lesion in T2, heterogeneous, with irregular borders involving more than 60% of the vertebral body of L4 with invasion of the spinal canal causing compression to the roots. He was treated with an L4 spondylectomy and placement of intervertebral expander and posterior fixation.

CONCLUSION

Spondylectomy is an effective option for the treatment of spinal malignant fibrous histiocytoma that involves combined approaches. However the challenge is greater since it requires a knowledge of the great abdominal vessels and multidisciplinary intervention.

Malignant transformation of polyostotic fibrous dysplasia with aberrant keratin expression

Malignant transformation of fibrous dysplasia (FD) is exceedingly rare, occurring in less than 1% of all FD cases, and has been described in both monostotic and polyostotic forms of this entity. We report a case of a large proximal femur mass arising in a 45-year-old man. The biopsy revealed a high-grade pleomorphic malignancy that focally expressed multiple keratins. Based on the presence of keratin immunoreactivity, the morphologic differential diagnosis included metastatic sarcomatoid carcinoma. However, review of the clinical information revealed a history of polyostotic FD, and imaging findings were compatible with malignant transformation of FD. The resected neoplasm was biphasic and composed of areas of conventional FD admixed with a high-grade pleomorphic malignancy. Activating GNAS mutations were identified in both components. To the best of our knowledge, this is the first description of keratin expression in malignant transformation of FD.

Double primary malignant fibrous histiocytoma and squamous cell carcinoma of the larynx treated with laser laryngeal conservation surgery

ΒACKGROUND

Synchronous multiple malignancies of the larynx are rare. We present a case here of synchronous primary laryngeal squamous cell carcinoma (SCC) and malignant fibrous histiocytoma (MFH) in a patient with hoarseness though with no history of exposure to radiation. Clinical, intraoperative, and histopathological findings in this patient are discussed.

METHODS

Wide laser excision of the left supraglottic lesion and laser cordectomy of the right true vocal cord were performed.

RESULTS

The patient presented with a recurrence of the ΜFH alone (with no recurrence of the SCC) two months after the first operation and was managed with an extended second look laser cordectomy. The patient is under regular follow-up and remained disease-free nine months from diagnosis.

CONCLUSIONS

Our results show that early-stage simultaneous tumours of the larynx and particularly MFH and SCC can be treated efficiently with endoscopic laryngeal surgery alone. Close follow-up is of paramount importance because of the aggressive nature of MFH.

An approach to pleomorphic sarcomas: can we subclassify, and does it matter?

The term malignant fibrous histiocytoma (MFH) has been supplanted by undifferentiated pleomorphic sarcoma (UPS). Even now, however, a number of pleomorphic neoplasms are classified as UPSs when in fact at least a subgroup of these can be more precisely classified as a pleomorphic sarcoma with a specific line of differentiation. Still others are pseudosarcomas, most commonly sarcomatoid carcinomas. This review will discuss historical aspects of MFH/UPS as well as provide an approach to the pleomorphic malignant neoplasm with a discussion of useful ancillary techniques in the evaluation of such cases.

Malignant fibrous histiocytoma of the spine: a series of 13 clinical case reports and review of 17 published cases

STUDY DESIGN

Retrospective case study of 13 primary malignant fibrous histiocytomas (MFH) of the spine.

OBJECTIVE

To analyze the clinic, radiologic, histologic, and prognostic features of 13 cases with the MFH of the spine.

SUMMARY OF BACKGROUND DATA

MFH, a soft tissue sarcoma, rarely occurs at the spine. Only sporadical cases have been reported in the English literature concerning the clinical and prognostic features of the primary MFH at the spine.

METHODS

Between January 1999 and December 2006, 13 cases with primary MFH of the spine were treated in the authors' spine center. Clinical history, radiographic, surgery resection, and pathologic features were recorded. The patients were followed up regarding their local recurrence and survivals. The 17 cases with primary MFH at the spine in the literature were reviewed.

RESULTS

Paraspinal or epidural mass at multiple spinal levels developed in 11 cases, with osteolytic destruction in all 13 cases. The tumor size averaged on 10.4 cm in greatest dimension. Metastases occurred in 10 of 13 cases. Compared with the 14 ± 0.60-months median survival of the debulking surgeries in seven cases, the median survival of the en bloc resection in six cases was 25 ± 6.12 months (P ∇ 0.009). The median survival was 8.7 months in 10 cases of the literature group, with 30% 1-year survival and 6.7% 2-year survival, respectively; while the median survival was 18.0 months in the authors' series, with 92.3% 1-year survival and 38.5% 2-year survival, respectively. The 5-year survival was between 25% and 69% in the extremities of MFH, but it was 28% in the head and neck and 26.7% in the abdominal cavity, compared with 7.7% in the spine in the authors' series.

CONCLUSION

The MFH of the spine tends to extensively invade paraspinal structures at multiple spinal levels, with aggressive osteolytic destruction in the vertebrae, resulting to local huge mass, radiculopathy, and myelopathy. Regardless of recent advancements in the diagnosis, treatment methods, and adjuvant therapies, for its biologically aggressive nature, it frequently recurs at the primary site and metastasizes. It has a worse prognosis than that of MFH in other sites.

Immunohistochemistry in diagnosis of soft tissue tumours

Immunohistochemistry in soft tissue tumours, and especially sarcomas, is used to identify differentiation in the neoplastic cells. In some cases, specific antigens are expressed; however, an initial panel of antibodies is often required in order to establish the broad lineage, with a subsequent, more focused, panel to allow classification. Immunohistochemical evaluation must be employed with the clinical picture, the morphology, and, when necessary, other ancillary techniques such as molecular genetics and cytogenetics. Whereas some diagnoses are evident on morphology, many soft tissue neoplasms are seen microscopically as spindle cell, epithelioid cell, small round cell or pleomorphic tumours that need to be further characterized. This article reviews selected applications of immunohistochemistry in the diagnosis of each of the principal morphological groups, concentrating on areas of most use in daily practice.

Transformation potential of bone marrow stromal cells into undifferentiated high-grade pleomorphic sarcoma

PURPOSE

Bone marrow adherent cells contain conventional bone marrow stromal cells and mesenchymal stem cells and these cells constitute the hematopoietic microenvironment. Mesenchymal stem cells have the capacity to give rise to multiple mesenchymal lineage cells and even ectodermal lineage cells. In the present study, we investigated what types of tumor cells are inducible from BM adherent cells by chemical carcinogens.

METHODS

Bone marrow cells from neonatal C3H/HeN mice were collected within 24 h after birth and then cultured. Four days later, bone marrow adherent cells were obtained and the cells were treated with 3-methylcholanthrene.

RESULTS

By this treatment, some transformed clones consisting of large spindle cells were obtained. The transformed cells were highly positive for CD44 and were positive for Sca-1, CD49d and CD106, whereas the cells were negative for hematolymphoid markers. The cell clones had the ability to support hematopoiesis in vitro. These results indicate that the transformed cell lines have the characteristics of BM stromal cells/mesenchymal stem cells. Moreover, during culture of the transformed cells, spontaneous bone nodule formation was observed. When the transformed cells were inoculated into immunodeficient mice subcutaneously, the neoplasms grew in the subcutaneous tissue of the mice. Microscopically and ultrastructurally, the neoplasms showed the typical morphology of undifferentiated high-grade pleomorphic sarcoma (UHGPS). Bone-related genes have been found to be expressed in both transformed cells and UHGPSs.

CONCLUSION

The present study suggests that UHGPSs are derived from BM stromal cells, probably mesenchymal stem cells.

The Rise and Fall of Malignant Fibrous Histiocytoma

The term malignant fibrous histiocytoma was coined by Stout and associates in the 1960s to encompass pleomorphic soft tissue sarcomas presumably derived from histiocytes that are capable of fibroblastic transformation. The concept was reaffirmed in the following 2 decades and malignant fibrous histiocytoma thus was regarded as the most common soft tissue tumor in older adults. However, recent more critical clinicopathologic, ultrastructural, and immunohistochemical studies have shown that malignant fibrous histiocytomas are not derived from histiocytic "facultative fibroblasts" and many neoplasms so diagnosed actually are pleomorphic subtypes of other sarcomas. Meticulous electron microscopic and immunohistochemical investigations also found that the more common storiform-pleomorphic, myxoid, and perhaps the giant cell subtypes are composed of variable mixtures of fibroblasts and phenotypically modulated fibroblastic cells, notably myofibroblasts and histiofibroblasts. On the basis of these findings, we propose a new classification for the above subtypes of so-called malignant fibrous histiocytoma, the majority of which are variants of pleomorphic fibrosarcoma.

CD99 immunoreactivity in atypical fibroxanthoma and pleomorphic malignant fibrous histiocytoma: a useful diagnostic marker

Atypical fibroxanthoma (AFX), a benign lesion, and pleomorphic malignant fibrous histiocytoma (MFH) are thought to represent points along the same neoplastic spectrum but with different prognoses and treatments. Diagnosis based on histology and clinical parameters alone is sometimes difficult, and a reliable cost-effective immunohistochemical marker to help distinguish these lesions would be beneficial. The diagnosis of AFX or MFH was based upon published clinical and microscopic criteria. Formalin-fixed, paraffin-embedded tissues of 17 cases of AFX and 26 cases of MFH were immunostained with monoclonal antibody to CD99. For all cases, CD99 expression was scored on a four-tiered scale: negative, weak (1+), moderate (2+), or strong (3+). Two pathologists blinded to tumor diagnoses and type of immunostain evaluated each case independently. The interobserver correlation coefficient was calculated. Seventeen patients with AFX (16 males and one female; mean age = 79) and 26 patients with MFH (16 males and 10 females; mean age = 60) were included. AFX lesions were from the head and the face, mean size = 1.5 cm, and MFH lesions were from the head, the neck, the trunk, and the upper/lower extremities, mean size = 5.2 cm. The 17 cases of AFX demonstrated moderate or strong (2 to 3+) immunoreactivity with CD99, compared to nine of 26 (35%) MFH cases (chi-square = 18.38; p < 0.001; interobserver correlation coefficient = 0.83). Of these, 16 of 17 (94%) AFX cases stained diffusely with CD99, while only four of 26 (15%) MFH cases stained diffusely. Control slides were adequate. Our study demonstrated that CD99 can help distinguish AFX from MFH, in addition to other immunohistochemistry as well as clinical and histologic criteria.

The comparative roles of electron microscopy and immunohistochemistry in the diagnosis of soft tissue tumours

Electron microscopy has contributed to the diagnosis of soft tissue tumours for four decades, and immunohistochemistry for two. Because of its relative ease of use and interpretation, the latter technique has become extensively and routinely applied to identify lines of differentiation in benign soft tissue tumours and in sarcomas. The use of electron microscopy has declined but retains a role because few antibodies are wholly specific or fully sensitive, some tumours are polyphenotypic or divergent in differentiation, and others have no specific antigens. Immunohistochemistry is superior in diagnosis of smooth muscle tumours, small round cell tumours, sarcomas with epithelioid morphology, and most synovial sarcomas. Electron microscopy is of particular value for peripheral nerve sheath tumours, marker-negative synovial sarcomas, pleomorphic sarcomas and mesotheliomas. As with all adjunctive techniques, immunohistochemistry and electron microscopy should be used in a complementary fashion according to the nature of the diagnostic problem.

Myofibroblastic malignancies

Malignant tumors composed of myofibroblasts are increasingly being recognized, but their existence remains controversial. Currently accepted examples within this category represent spindle cell or pleomorphic neoplasms of the soft tissues with a spectrum of histological grades. Low- and intermediate-grade myofibrosarcomas are fascicular spindle cell neoplasms resembling fibrosarcoma or leiomyosarcoma. They infiltrate deep soft tissue with disproportionate involvement of head and neck sites and can recur locally but infrequently metastasize. They variably express myoid immunohistochemical markers, and their differential diagnosis includes benign myofibroblastic proliferations such as fasciitis and fibromatosis as well as other types of spindle cell sarcoma. High-grade (pleomorphic) myofibrosarcomas are an ultrastructurally defined subset of malignant fibrous histiocytoma, which they resemble in morphology and behavior. Inflammatory myofibroblastic tumor and infantile fibrosarcoma are neoplasms that have myofibroblastic features and have been included in this category, but they have distinctive genetic findings. This article reviews the concept of myofibrosarcoma and describes its variants.

Myofibrosarcoma

Myofibrosarcomas are malignant tumours of myofibroblasts, which have been recognised for many years, but have become clearly defined only recently. They are low- or high-grade sarcomas that arise in soft tissue or bone in adults or children. Low-grade myofibrosarcomas are infiltrative tumours, usually in deep soft tissue, with a predilection for the head and neck region, which display a range of microscopic appearances from fasciitis-like to fibrosarcoma-like; all cases at least focally display nuclear pleomorphism. They express smooth-muscle actin and calponin, and some express desmin, but most lack h-caldesmon. Low-grade myofibrosarcomas can recur but rarely metastasise. Their differential diagnosis is from benign myofibroblastic proliferations, such as fasciitis and fibromatosis, as well as from fibrosarcoma and leiomyosarcoma. Pleomorphic myofibrosarcomas are high-grade pleomorphic sarcomas (malignant fibrous histiocytoma), which show ultrastructural evidence of myofibroblastic differentiation. They closely resemble malignant fibrous histiocytoma clinically and morphologically, but are more frequently actin positive. This article describes the low- and high-grade variants of myofibrosarcoma and other malignant tumours with myofibroblastic differentiation.

Keratin expression in human tissues and neoplasms

Keratin expression in human tissues and neoplasms Keratin filaments constitute type I and type II intermediate filaments (IFs), with at least 20 subtypes named keratin 1-20. Since certain keratin subtypes are only expressed in some normal human tissues but not others, and vice versa, various tissues have been subclassified according to the pattern of keratin staining. Simple epithelia generally express the simple epithelial keratins 7, 18, 19, and 20, while complex epithelia express complex epithelial keratins 5/6, 10, 14, and 15. When an epithelium undergoes malignant transformation, its keratin profile usually remains constant. The constitution and expression patterns of keratin filaments in human epithelial neoplasms are complex and often distinctive. In this article, we first briefly review the molecular and cell biology of keratin filaments. We then focus on the expression patterns of keratin filaments in various human neoplasms.

Transdifferentiation of neoplastic cells

Transdifferentiation is a process in which a stable cell's phenotype changes to that of a distinctly different cell type. It occurs during certain physiological processes and leads to transition of tumor cell phenotypes. The latter process includes neoplastic epithelial-epithelial transition, neoplastic epithelial-mesenchymal transition, neoplastic mesenchymal-epithelial transition and transition between non-neural and neural neoplastic cell. This phonomenon is exemplified in some origin-debated tumors, such as carcinosarcoma, pleomorphic adenoma, synovial sarcoma, Ewing's/pPNET, and malignant fibrohistiocytoma. We propose that differentiation disturbance of cancer cells should include not only undifferentiation and dedifferentiation, but also transdifferentiation as well. Tumor cell transdifferentiation may be influenced or determined by cellular genetic instabilities, proliferation and apoptosis, as well as by extracellular matrix and growth factors.

Novel cell lines established from a human myxoid malignant fibrous histiocytoma arising in the uterus

Two cell lines (Nara-H and Nara-F) with different phenotypes were established from a myxoid MFH of the uterus. In vitro, Nara-F grew in sheets showing a storiform arrangement and Nara-H in raised colonies. Although tumors generated in nude mice shared similar morphological features of abundant myxoid tumor in Nara-H and -F, the pleomorphic component was conspicuous in Nara-F. Both cell lines produced hyaluronic-acid but CD44 was expressed only in Nara-H. Estrogen receptor alpha (ER alpha) and progesterone receptor (PgR) were detected in Nara-H. Nara-F was positive for ER beta and PgR. Among hormonal agents, the response to the anti-estrogen tamoxifen was more sensitive than progesterone agents. This report illustrates the characteristics of these newly established cell lines, and presents the possibility of an adjuvant hormonal therapy for MFH.

Immunohistochemistry in diagnostic dermatopathology

This article briefly reviews many immunohistochemical stains that have been in use for years, emphasizing their diagnostic use and potential pitfalls. Several newer immunostains are described in a more comprehensive fashion, including brief summaries from recently published studies.

Desmoplastic small round cell tumor: II: an ultrastructural and immunohistochemical study with emphasis on new immunohistochemical markers

In order to investigate the histogenesis and facilitate the diagnosis of desmoplastic small round cell tumor (DSRCT), 39 cases were studied by immunohistochemical methods using a large battery of antibodies directed against a wide variety of epithelial, mesenchymal, and neural-associated proteins. Sixteen of these tumors were also studied by electron microscopy. Thirty-seven of 39 cases reacted for cytokeratin using a "cocktail" of 3 monoclonal antibodies (CAM 5.2/AE1/AE3), 39/39 for desmin, 24/25 for epithelial membrane antigen, 22/27 for vimentin, 18/25 for neuron-specific enolase, 10/15 for CD57 (Leu-7), 3/19 for synaptophysin, 1/22 for chromogranin, 3/19 for muscle-specific actin, 3/16 for alpha-smooth-muscle actin, 11/16 for CD15 (Leu-M1), 5/12 for CA-125, 6/17 for CD99, 9/10 for MOC-31, 2/6 for NB84, 5/7 for Ber-EP4, and 8/9 for the Wilms tumor (WT1) protein. No staining was obtained in any of the cases tested for cytokeratin 5/6 or 20, neurofilament proteins, glial fibrillary acidic protein, peripherin, CA19-9, thrombomodulin, alphafetoprotein, carcinoembryonic antigen, TAG-72 (B72.3), placental alkaline phosphatase, S-100 protein, HMB-45, myoglobin, or for the two myogenic regulatory proteins myogenin and MyoD1. A frequent ultrastructural finding was the presence of juxtanuclear aggregates of intermediate filaments, but microfilaments with densities or Z-band-like material suggestive of either smooth or skeletal muscle differentiation were not seen in any case. Dendritic-like processes containing microtubules and dense core granules were seen in four tumors and all of these tumors reacted for at least one of the neural markers investigated. Although ultrastructural and immunohistochemical studies confirmed previous observations that DSRCTs present epithelial, mesenchymal, and neural phenotypes, a great variation was found in the frequency of expression of the different markers used to demonstrate each line of cell differentiation. The absence of expression of cytokeratin 5/6 and thrombomodulin together with positive staining for CD15, MOC-31, and Ber-EP4 argues against the possible mesothelial origin that has been suggested for this tumor. Additionally since none of the tumors reacted for myogenin or MyoD1, desmin expression in DSRCT cannot be regarded as evidence of skeletal muscle differentiation. Although the histogenesis of DSRCT remains unknown, it is believed that this tumor originates from a progenitor cell with potential for multiphenotypic differentiation.

LN-2 (CD74). A marker to distinguish atypical fibroxanthoma from malignant fibrous histiocytoma

BACKGROUND

In this study, the authors examined the expression of LN-2, an antigen expressed by B cells, macrophages, and Reed-Sternberg cells, in a variety of spindle cell lesions of the skin to determine whether LN-2 immunoreactivity can be used to differentiate among these tumors. For comparison, they examined CD34 antigen expression in these lesions, which has been shown to be a useful marker in differentiating dermatofibrosarcoma protuberans from dermatofibroma.

METHODS

Immunocytochemistry with anti-LN-2 and anti-CD34 monoclonal antibodies on formalin fixed, paraffin embedded material was performed on 102 spindle cell lesions, including dermatofibroma, dermatofibrosarcoma protuberans, atypical fibroxanthoma, malignant fibrous histiocytoma, leiomyoma, and neurofibroma.

RESULTS

LN-2 immunoreactivity did not distinguish between dermatofibroma and dermatofibrosarcoma protuberans, both of which showed weak immunoreactivity. In marked contrast, 90% of cases of malignant fibrous histiocytoma showed strong staining for LN-2, whereas the vast majority (90%) of cases of atypical fibroxanthoma were negative or stained only weakly with anti-LN-2 antibodies. Of the two cases of atypical fibroxanthoma that stained strongly for LN-2, both lesions were > 2 cm in size and extended deep into the subcutaneous fat.

CONCLUSIONS

Differential expression of the LN-2 antigen by atypical fibroxanthoma and malignant fibrous histiocytoma distinguishes these two lesions and suggests that acquisition of LN-2 positivity may be a marker of tumor progression.

Sarcomatoid carcinoma of the ampulla of Vater

Sarcomatoid carcinomas (carcinosarcomas) are rare lesions in the gastrointestinal tract, where they are most commonly found in the esophagus. We present the first reported case of a sarcomatoid carcinoma of the ampulla of Vater. The tumor was composed of intermixed carcinomatous (adenocarcinoma plus squamous cell carcinoma) and sarcomatous elements. Cytokeratin immunoreactivity was demonstrated focally in the sarcomatoid component, although in other areas there was positive staining for desmin and smooth muscle actin. The possible histogenesis of such lesions is briefly discussed.

Tenascin expression in cutaneous fibrohistiocytic tumors. Immunohistochemical investigation of 24 cases

We studied the immunolocalization of the extracellular matrix glycoprotein tenascin in a series of 24 cutaneous fibrohistiocytic tumors, including seven benign lesions (benign fibrous histiocytoma/dermatofibroma), six intermediate malignancy lesions (dermatofibrosarcoma protuberans), and 11 malignant lesions (three atypical fibroxantomas and eight malignant fibrous histiocytomas). The results of the immunohistochemical staining were evaluated semiquantitatively. All lesions expressed tenascin in the extracellular matrix, with some differences in the distribution of the immunoreactivity. In benign fibrous histiocytoma and in dermatofibrosarcoma protuberans, there was a homogeneous, intense, and diffuse staining of the extracellular matrix (++); the only exception was the homogenized, sclerotic collagen present in late, regressing benign fibrous histiocytoma, which showed a weak and patchy reactivity (+). In atypical fibroxantomas and in malignant fibrous histiocytomas, there was an irregular distribution of the positivity within the tumor matrix (+). Prominent staining of the cytoplasm of several neoplastic cells was observed in atypical fibroxantoma and malignant fibrous histiocytoma (++), focal cytoplasmic staining of scattered cells was found in dermatofibrosarcoma protuberans (+), and cytoplasmic staining was absent from benign fibrous histiocytoma (-). These findings indicate a relationship between cytoplasmic and extracellular matrix expression of tenascin in these lesions, with an increase in cytoplasmic staining and a decrease in extracellular matrix staining in the malignant forms. Based on these different staining patterns, tenascin immunolocalization could furnish some help in the differential diagnosis among benign, intermediate malignancy, and malignant cutaneous fibrohistiocytic tumors. Moreover, the intense tenascin staining at the edge of the lesion could be helpful in defining its extent and therefore provide an additional criterion to evaluate the radicality of the surgical procedure.

Oral post-radiation malignant fibrous histiocytoma: a clinicopathological study

Five cases of oral malignant fibrous histiocytoma (MFH) in patients who had previously received radiotherapy in the head or neck region were included in this study. There were 3 men and 2 women. Four patients had been irradiated for nasopharyngeal carcinoma (NPC) and the other for a squamous cell carcinoma (SCC) involving the tongue and mouth floor. The MFH developed 2.5-11 years after the initial radiotherapy. Two cases of MFH occurred in the maxilla, two in the mandible, and the remaining one in the tongue, floor of mouth and mandible. Clinically, the oral post-radiation MFH presented as tender, reddish, elastic, lobulated masses with surface ulceration. Radiographic examination of the involved jaws revealed a poorly defined radiolucent lesion without any periosteal or endosteal reaction. The prognosis of these tumors was very poor. Although aggressive multimodality treatment had been applied, 3 of 5 patients eventually died of the disease, with a mean survival time of 17 months after establishing the diagnosis of MFH. In order to ensure the early diagnosis and treatment of this radiation-induced second malignancy, close oral follow-up is mandatory for patients who have received radiotherapy for head and neck malignancies.

Fibronexus in a case of malignant fibrous histiocytoma

A 78-year-old man presented with a subcutaneous supraorbital tumor measuring approximately 4.0 x 3.0 x 1.8 cm. It was removed in several irregular portions, and histologic sections were taken from each portion. The lesion was diagnosed as a grade 3 malignant fibrous histiocytoma. Further characterization of the tumor necessitated the use of transmission electron microscopy. This appears to be the first report of fibronexus in malignant fibrous histiocytoma. This structure linked the myofibroblast with the extracellular matrix; specifically, microfilaments were linked to fibronectin fibrils. Interaction between collagen and fibronectin was noted within the extracellular matrix.

Immunohistochemical staining of feline malignant fibrous histiocytomas

Malignant fibrous histiocytoma was diagnosed in seven cats from biopsy specimens received at the University of Missouri Veterinary Medical Diagnostic Laboratory during a 4-year period from 1987-1991. Tissue blocks from formalin-fixed specimens were resectioned and stained for type I (AE1) and type II (AE3) cytokeratins, desmin, S100 protein, vimentin, and alpha 1-antitrypsin by the avidin biotin peroxidase complex method with diaminobenzidine (DAB) chromogen. None of the tumors stained positively for alpha 1-antitrypsin. Four of seven of the tumors had similar immunohistochemical staining results, with positive staining for type I and type II cytokeratins, desmin, S100 protein, and vimentin. Of the remaining three, one stained positively only for S100 protein and vimentin; one stained positively for vimentin only; and one was negative for all six antigens. Based only on immunohistochemical staining results, three of the tumors could possibly be reclassified: one as a melanoma, one as a probable fibrosarcoma, and one as unknown. These results also indicate that feline malignant fibrous histiocytomas show a diversity of intermediate filament expression, as do human tumors. Our results also do not support the theory that malignant fibrous histiocytomas are of histiocytic origin.

Tumor cells induced by the v-src oncogene are heterogeneous for expression of markers of mesenchyme differentiation

The observation that v-src-induced tumors contain tumor cells of differing morphology, notably fibroblastoid or polygonal, raised the question as to whether the tumor cells are also heterogeneous with respect to expression of markers of cellular differentiation. Of the markers tested here, consistent reactivity for tumor tissue was noted only for antibody probes reactive to muscle actin (HHF35, alpha sm-1) or to procollagen type I (SP1. D8); for any given tumor, whether induced by v-src DNA or by Rous sarcoma virus, each of these markers was found only in a subpopulation of tumor cells. The observation of marker heterogeneity in the one v-src DNA-induced tumor examined here that typed as monoclonal suggests that v-src-induced transformation is consonant with a degree of plasticity in the phenotypes of the clonal progeny of a single transformant.

Benign fibrous histiocytoma of the stomach: report of a case

We report herein an extremely very rare case of primary benign fibrous histiocytoma of the stomach found in a 56-year-old man who presented with a 2-week history of nausea and anorexia. Gastrointestinal X-rays and endoscopy revealed a protruding lesion in the stomach, but biopsies failed to demonstrate the nature of the tumor. Histopathologic investigation of the resected tumor showed the typical features of benign fibrous histiocytoma: Consisting of an admixture of spindly fibroblast-like and roundish histiocyte-like cells arranged in a storiform pattern. Furthermore, immunohistochemical staining with alpha-1-antichymotrypsin was positive for histiocyte-like cells in the tumor. The patient has shown no evidence of recurrence in the 2 years of follow-up since his operation.

Immunoreactivity to cytokeratins in non-epithelial cells in deep gastric ulcer

The finding of cytokeratin positivity in non-epithelial cells in 9/15 cases of performing or penetrating gastric ulcer is reported. Two different monoclonal anti-cytokeratin antibodies were used and both produced a strong positivity in spindle and polyglonal cells in the gastric wall. These cells were often distributed near the peritoneal surface, but they were also found in central parts of the gastric wall. The cytokeratin-positive cells had no connection with the gastric mucosa, lacked epithelial features in routinely stained sections and were not positively stained by antibodies to other epithelial markers (EMA and Ber-Ep 4). Many of the cytokeratin-positive cells were also positive for vimentin. There was no evidence of malignancy in any of the cases, but cytokeratin-positive cells like those in the present study may be erroneously interpreted as infiltrating carcinoma. The true nature of the cytokeratin-positive cells was not revealed in the present study. It is concluded that cytokeratin positivity must be evaluated with care and that it is valuable to add antibodies other than anti-cytokeratins for the recognition of epithelial cell differentiation.

Malignant fibrous histiocytomas in dogs and cats: an immunohistochemical study

Immunohistochemical staining was performed on seven canine and 10 feline soft tissue tumours histologically diagnosed as malignant fibrous histiocytomas (MFHs) or MFH-like tumours, and eight other histologically specified tumours (non-MFH). This was done to determine if commercially available antibodies that are used routinely in human diagnostic pathology for MFHs would express the same immunohistochemical patterns in canine and feline MFHs and MFH-like tumours. The antibodies were directed against human alpha 1-anti-trypsin (AT), human alpha 1-anti-chymotrypsin (ACT), human lysozyme, bovine S-100 protein and human desmin. AT did not show any immunoreactivity in the tissues investigated. Except for one MFH, all canine MFHs and other soft tissue tumours with a 'histiocytic' character stained for lysozyme and not for S-100. Six out of seven canine MFHs and MFH-like tumours stained positive for desmin as did most non-MFH sarcomas. Most of the canine and feline MFHs and MFH-like tumours were positive for ACT. These findings for ACT staining in canine and feline MFHs and MFH-like tumours are in agreement with the findings in human MFHs. The immunohistochemical results of canine MFHs and MFH-like tumours were different from those in cats. Feline MFHs differed from canine MFHs for both lysozyme and desmin staining.

Osteogenic sarcoma with epithelial differentiation

This case report details an osteogenic sarcoma arising in a vertebra in which cytokeratin intermediate filaments were detected immunohistochemically with three different antibodies. This feature was present not only in the primary neoplasm but also in two local recurrences and a metastasis to the iliac bone. What is unique about this primary bone tumor, however, is the structural evidence for epithelial differentiation. Ultrastructurally, well-formed desmosomes and tonofilaments were present in all four surgically resected specimens. This tumor expands the list of soft tissue and bone tumors in which anomalous expression of intermediate filaments can occur but, more important, illustrates that changes in genetic expression of neoplasia of mesenchymal origin can result in paradoxic epithelial differentiation.

Morphological heterogeneity and phenotypical instability versus metastatic stability in the murine tumor model ER 15-P

At clinical presentation, the majority of malignant tumors are composed of multiple clonal subpopulations of tumor cells with different phenotypic characteristics. Using the experimental tumor model ER 15-P, a methylcholanthrene-induced pleomorphic sarcoma of the C57 Bl6J mouse, we studied a system of long-term in vivo passages of this primary tumor for cell morphological changes, and alterations in the potential for spontaneous lung metastases. Transplants from the primary after the 4th, 20th, 40th and 80th i.m. passage (referred to as T4, T20, T40, and T80 respectively) together with their lung metastases were investigated by light microscopy, immunohistochemistry, and electron microscopy. In addition, the potential for metastasis to the lungs in each group was determined and compared with that of the parent T4 tumors. T4 tumors were mainly composed of spindle-shaped tumor cells with the ultrastructural features of fibroblasts and myofibroblasts, often arranged in a storiform or fasciculated growth pattern, and intermingled with tumor giant cells. Some small areas contained polygonal or rounded tumor cells, ultrastructurally undifferentiated, and sometimes arranged in a hemangiopericytoma-like growth pattern. Although electron-microscopical findings clearly demonstrated the mesenchymal origin of these tumor cells, immunostaining with a polyclonal antibody to vimentin was unspecific in all tumor cells and normal mouse tissue. Monoclonal antibodies to vimentin from different sources were completely negative in tumor cells and murine stromal components. In contrast, myofibroblast-like tumor cells showed immunohistochemically, a moderate to strong co-expression with monoclonal antibodies to desmin, muscle actin and alpha-smooth muscle actin. On the basis of these morphological findings, the primary ER 15-P was classified as a pleomorphic myofibrosarcoma. The lung metastases of T4 tumors were mainly composed of undifferentiated round to polygonal tumor cells, while the number of desmin-positive, muscle- and alpha-smooth muscle-actin-positive cells was reduced. The morphological features of T20 tumors and their lung metastases were the same as in T4, indicating a relative stability of the phenotype up to that stage. In contrast, T40 and T80 tumors and their lung metastases were found to contain almost exclusively undifferentiated tumor cells and many tumor giant cells. While fibroblast-like tumor cells were seen only occasionally, myofibroblast-like tumor cells had almost completely disappeared. The potential for lung metastases was nearly constant in all groups, suggesting metastatic stability. Obviously, the undifferentiated tumor cells of this model are associated with a higher metastatic potential.

The fibroma-like variant of epithelioid sarcoma

Five cases of a previously undescribed variant of epithelioid sarcoma are presented. This variant differs from the usual lesion in its absence of the typical necrobiotic nodular epithelioid pattern. It is instead composed of deceptively bland fibrohistiocytic and myoid cells arranged in a fibroma-like or dermatofibroma-like pattern with an affinity for osseous involvement. The clinical presentation, ultrastructural features, and presence of vimentin and low molecular weight keratin within the tumor cells justifies their designation as an epithelioid sarcoma variant.

Epithelial and melanoma antigens in gliosarcoma. An immunohistochemical study

Gliosarcomas are mixed tumors with malignant glial and mesenchymal elements. The number of GFAP-positive tumor cells decreases with the increase of sarcomatous components, until whole areas may be GFAP negative. These distinct differentiations may, however, lead to false interpretations in small tissue samples. In this connection, it is of interest that, according to other reports, glial tumors may be positive for different anti-keratin antibodies and this prompted us to undertake a systematic investigation of the immunoreactivity of gliosarcomas using a panel of well-characterized monoclonal antibodies against cytokeratins (KL1, AE 1/3, Lu-5, CK-19, CK MNF 116 and Ma-903). These cases were further studied with the anti-epithelial non-cytokeratin antibodies EMA, HEA 125, Ber-EP4, CEA as well as the melanoma-antibody HMB-45, Leu-M1, GFAP and vimentin. As screening study we examined 20 cerebral metastatic carcinomas, 21 malignant gliomas (including 6 gliosarcomas) and 3 metastatic melanomas with the monoclonal antibodies KL1 and HMB-45. All cerebral metastatic carcinomas and 4/6 gliosarcomas were positive for KL1, whereas all melanomas, 2 metastatic carcinomas and 3 gliosarcomas showed an immunostaining with HMB-45. All gliosarcomas were positive with at least one of the tested anti-cytokeratin antibodies. The gliosarcomas did not show an immunoreaction in any of the cases when CEA, HEA 125, Ber-EP4, EMA or Leu M1 were applied. In our opinion, the monoclonal antibodies HEA 125 and Ber-EP4 could obviously be helpful in differentiating gliosarcomas from metastatic carcinomas.

Peripheral nerve sheath differentiation in malignant soft tissue tumours: an ultrastructural and immunohistochemical study

Thirteen soft tissue sarcomas with ultrastructural evidence of nerve sheath differentiation were investigated by immunohistochemistry. Three arose in a major nerve or nerve trunk and four patients had von Recklinghausen's neurofibromatosis. Ultrastructurally, 10 cases showed variable differentiation towards Schwann cells, two resembled perineurial cells and one tumour had features suggestive of both cell types. Immunostaining for S-100 protein was positive in eight Schwann cell tumours, negative in the other two Schwann cell tumours and negative in those with perineurial-like cells. No cases demonstrated epithelial membrane antigen, so that the existence of perineurial cells in malignant nerve sheath tumours remains immunohistochemically unsubstantiated; it may be that the perineurial-like cells are merely incompletely differentiated Schwann cells, with nerve sheath differentiation manifesting a continuous spectrum. Leu 7 was detected in four Schwann cell tumours, three of which were ultrastructurally well differentiated. Cytokeratin and desmin were demonstrated only in an undifferentiated pleomorphic area of one Schwann cell tumour. Electronmicroscopy can aid diagnosis by revealing nerve sheath differentiation in malignant soft tissue tumours without demonstrable S-100 protein.

Two cell lines with epithelial cell-like characteristics established from malignant fibrous histiocytomas

Two malignant fibrous histiocytoma (MFH) cell lines were established: one from a storiform-pleomorph subtype and the other from a myxoid one (codes, MFH-3 and MFH-4). Light microscopic examination revealed large rounded cells, growing mostly separately, in both cell lines. Their ultrastructure was different in various aspects. The MFH-3 cells showed abundant lysosomal activity, a well-developed Golgi apparatus, and a few desmosome-like cell contacts. The MFH-4 cells had a well-developed rough endoplasmic reticulum, delicate bundles of tonofilaments, the formation of pseudoacini, and the presence of small completely developed desmosomes. Based on immunostaining and immunoblotting assays of cultured cells, both cell lines expressed immunoreactivity for vimentin; cytokeratins 7, 8, and 18; desmin; and laminin, but they lacked reactivity for cytokeratins 10 and 19, neurofilament, alpha-smooth muscle actin, S-100 protein, collagen type IV, carcinoembryonic antigen, and antigens specific for macrophages. Fibronectin and, to a variable extent, glial fibrillary acid protein and epithelial membrane antigen (EMA) were detectable in MFH-3 cells only. Furthermore, a 60-kilodalton band was present in both cell lines which was reactive for cytokeratins 8 and 18. The MFH-3 cells had the capacity to grow as xenografts with a carcinoma-like pattern. The cells retained their immunoreactivity for vimentin and cytokeratin 8 and showed the presence of desmosomes. Several of these immunophenotypic features also were noticed in established sarcoma cell lines and in short-term cultures of fibroblasts, smooth muscle cells, and endothelial cells. However, experimental data on the two MFH cell lines show that the MFH cell line may express some immunophenotypic and ultrastructural features considered to be specific for epithelial cells. The MFH cells may originate from multipotential mesenchymal cells with a capacity to differentiate to fibroblast-like cells, and less frequently, to epithelial cells, smooth muscle cells, and Schwannian cells. Such a differentiation became evident when these cells were adapted to culture conditions or grew in nude mice.

Intermediate and fine cytofilaments in cutaneous and subcutaneous leiomyosarcomas

The expression of fine and intermediate cytofilaments in 10 cutaneous and seven subcutaneous leiomyosarcomas was studied immunohistochemically. All the tumors contained tumor cells which showed a positive immunoreactivity for desmin in formaldehyde-fixed and paraffin-embedded sections, but none of the seven anti-desmin antibodies used alone produced a distinct positive staining in all the tumors. A lack of correspondence in terms of immunoreactivity between tumor cells and the supposed muscle of origin was observed, especially in the subcutaneous leiomyosarcomas. In all cases, antibodies to muscle-specific and smooth muscle-specific actin were found to produce a positive staining in both the tumors and the supposed muscle of origin. Vimentin was detected in 8/10 cutaneous and 4/7 subcutaneous leiomyosarcomas, while the supposed muscle of origin was positive in 3/10 and 7/7 cases, respectively. Four of the cutaneous and three of the subcutaneous leiomyosarcomas contained tumor cells which stained positively for cytokeratins, while the supposed muscle of origin showed no positivity. It thus appears that a phenotypic shift in terms of vimentin and cytokeratin expression occurs in the tumor cells of cutaneous and subcutaneous leiomyosarcomas compared with the supposed muscle of origin. It is recommended that more than one monoclonal anti-desmin antibody is used to characterize these tumor entities. It is also concluded that the immunoreactivity for muscle-specific actins in superficial leiomyosarcomas is more constant, although less specific, than that of desmin and that the demonstration of the simultaneous expression of muscle-specific actins and desmin is helpful.

Mac387: its non-specificity as a tumour marker or marker of histiocytes

A commercially available monoclonal antibody which detects histiocytes in paraffin sections, Mac387, was reacted with 148 soft tissue sarcomas, 29 carcinomas and 10 malignant melanomas. The soft tissue sarcomas had been previously immunophenotyped. All categories of sarcomas, with the exception of angiosarcomas, were positive. Most showed staining in less than 50% of the tumour cells. Six of 10 adenocarcinomas and three of nine basal cell carcinomas were positive, while squamous carcinomas and malignant melanomas were negative. Normal squamous mucosa and epidermis were also positive. The results of this study suggest that Mac387 is of little value in the differential diagnosis of soft tissue tumours, nor is it a specific histiocytic marker.

An immunohistochemical study of sarcomatoid liver carcinomas

Six cases of primary hepatic carcinomas with a significant amount of sarcomatoid elements were examined by using immunohistochemical stainings. Four of the six cases were associated with ordinary hepatocellular carcinoma (HCC), one with cholangiocellular carcinoma (CCC), and one with mixed HCC and CCC. Alpha-fetoprotein and alpha-1-antitrypsin were negative in sarcomatoid cells of all cases; vimentin stained positively in sarcomatoid tumor cells in two of the six cases; and cytokeratin (CK8) was detected in five cases. The CK8 was not detected in tumor cells of two cases of hepatic angiosarcoma, two of metastatic leiomyosarcomas, and one of metastatic fibrosarcoma, although vimentin stained positively in all these true sarcomas. It was concluded that sarcomatoid dedifferentiation of liver carcinomas might derive from both HCC and CCC. In addition CK8 might be an excellent marker to make a differential diagnosis of sarcomatoid cancers from true metastatic or primary sarcomas of the liver.

Towards the phenotyping of soft tissue tumours by cell surface molecules

This study is aimed at the characterization of soft tissue tumours (STT) by means of cell surface molecules. To achieve this, normal mesenchymal tissues were extensively examined for expression of leucocyte differentiation (CD) antigens and HLA molecules. The panel of antigens finally examined in STT comprised CD10, CD13, CD24, CD34, CD36, CD56, CD57, HLA-A,B,C, beta 2-microglobulin, HLA-DR, -DP, and -DQ and the HLA-D-associated invariant chain (Ii). STT were determined by conventional histomorphological and immunohistochemical criteria. The immunohistological analysis was based on serial frozen sections, one of which was used to demonstrate CD53 antigen. This very broadly distributed leuco/histiocyte-restricted antigen allowed for the distinction between the background of interstitial "stromal" cells and the neoplastic population. In some STT, the expression pattern of the cell surface molecules corresponded to that in their non-neoplastic counterparts. The majority of STT, however, showed considerable changes in the cell surface immunophenotype compared to their cells of origin. These alterations consisted mainly in an aberrant induction/neoexpression and, to a much lesser extent, in an aberrant down-regulation/loss of cell surface antigens. Nevertheless, some immunophenotype configurations are described which, for the time being, can be considered to be useful supplements in the differential diagnosis of this complex class of tumours. The data also indicate considerable changes in cell surface antigen expression occurring in the course of neoplastic transformation of mesenchymal cells. Detailed analysis of alterations in the functional repertoire of neoplastic mesenchymal cells might provide new insights into the biology of STT, possibly leading to new concepts for therapeutic intervention.