Malignant fibrous histiocytoma: histomorphological pattern or tumor type

Pleomorphic spindle cell sarcoma (PSCS) formerly known as malignant fibrous histiocytoma (MFH): a complex malignant soft-tissue tumor

A presentation defining the nature, characteristics, causation, treatment and outcome of patients with lesions formerly known as malignant fibrous histiocytoma and now as pleomorphic spindle cell sarcoma is clearly a very difficult subject. Many authors do not believe that the tumor exists and instead describe them as forms of fibrosarcomas, fibromyxoid lesions, dedifferentiated chondrosarcomas or even leiomyosarcomas. The reasons for this confusion are presumably related to the fact that the malignant pleomorphic spindle cell sarcoma does not seem to be a distinct type of lesion with specific histologic and genetic characteristics. Instead, the tumor has at least four separate histologic variations and no specific gene signature and in fact does not seem to be either familial or ethnic in presentation. In view of the fact that the tumor was traditionally the most frequently encountered malignant soft-tissue neoplasm, the world of orthopedic oncology is clearly distressed by the problems that these patients have and is joined by the radiation oncologists and chemotherapists in seeking new solutions.

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.

Growth effects of insulin and insulin analogues

The definition of mitogenic activity of insulin is controversial. Under physiological conditions, mitogenic refers to cell proliferation and tissue repair. In pathological conditions, it may refer to stimulation of tumour cells in pre-existing (undiagnosed) tumours. The in vitro investigations using benign and malignant cell lines compare proliferative activity of insulin molecules (animal, human and analogues). In these studies, inclusion of [B10-Asp] insulin would be a valuable link to the existing evidence on proliferation of mammary tissue in rodents. Animal and human insulin have growth promoting activity on spontaneously arising tumours (e.g. mammary tumours in rodents). They have no carcinogenic activity (cell transformation), and moreover insulin is not a co-carcinogen when evaluated in special toxicology. Mitogenicity (growth promoting activity) of insulin may be a problem in people with undiagnosed tumours, and may require definition of patient groups who would benefit from targeted monitoring.

Das maligne fibr�se Histiozytom

The entity and nosology of pleomorphic malignant fibrous histiocytoma (MFH) is still ambiguous. The actual WHO-Classification uses pleomorphic malignant fibrous histiocytoma (MFH) and pleomorphic sarcoma NOS (not otherwise specified) synonymously. On the other hand text and illustrations convey the impression, that these tumors also could be pleomorphic lipo-, leio- or rhabdomyosarcomas etc. It would have been more informative to emphasize, that with the above mentioned specific sarcoma types MFH-like appearance may occur. Furthermore it would have been more up to date to consider pleomorphic sarcomas NOS as pleomorphic fibrosarcomas and include them in the chapter of fibroblastic and myofibroblastic tumors. This concept already has been carried out for the former myxoid variant of MFH, nowadays preferentially called myxofibrosarcoma. There is controversial discussion about the clinical significance of exact typing of pleomorphic sarcomas. Problems may also occur due to the lack of standards, which degree of desmin expression signifies leiomyosarcoma or just indicates myofibroblasts in MFH. The requirement of exclusion of other tumor-types before diagnosing pleomorphic fibrosarcoma still remains obligatory. After verification of the diagnosis pleomorphic sarcoma NOS or pleomorphic fibrosarcoma, grading e.g. according to criteria of the FFCCS can be carried out. Most cases of pleomorphic fibrosarcoma will qualify as high grade malignant.

Leiomyosarcoma and malignant fibrous histiocytoma share similar allelic imbalance pattern at 9p

Formalin-fixed, paraffin-embedded tissue from 45 soft tissue sarcomas was analysed for allelic imbalance/loss of heterozygosity (AI/LOH) of chromosome 9. The specimens consisted of 17 cases of soft tissue leiomyosarcoma (LMS), 4 cases of cutaneous LMS, 22 cases of conventional malignant fibrous histiocytoma (MFH) and 2 cases of angiomatoid fibrous histiocytoma. All cases were categorised morphologically and immunohistochemically. DNA was microdissected from normal and neoplastic tissues. AI/LOH was performed using six microsatellite markers on the 9p region. The frequency of allelic imbalance at different loci on chromosome 9p was analysed in LMS and MFH and then compared with values previously examined in synovial sarcoma and malignant peripheral nerve sheath tumour. Although AI/LOH and microsatellite instability (MSI) were more frequent in MFH, LMS and MFH groups showed similar patterns of allelic imbalance at the 9p region. Alterations of chromosome 9p have been reported in many cell lines and tumours including LMS and MFH. 9p21 region encodes p16(INK4A) and p15(INK4B). Allelic imbalance observed at 9p 21 in this study suggests that alterations of the negative cell cycle regulators may be an important step in the pathogenesis of MFH and LMS. However, the most frequent allelic imbalance was observed at 9p24 at D9S230. Alterations of this locus were very rare in synovial sarcoma and malignant peripheral nerve sheath tumours and were absent in cutaneous LMS and angiomatoid fibrous histiocytoma. This locus may point to the existence of a genetically altered tumour suppressor gene involved in the pathogenesis of LMS and MFH. Our results support the hypothesis that MFHs may represent a morphological pathway in tumour progression of LMSs.

Inclusion of malignant fibrous histiocytoma in the tumour spectrum associated with hereditary non-polyposis colorectal cancer

Sarcomas, including the malignant fibrous histiocytomas (MFHs), are not known to be part of the tumour spectrum of hereditary non-polyposis colorectal cancer (HNPCC) as epidemiologically established. Therefore, occurrence of MFH in an HNPCC family may very well be coincidental. HNPCC is associated with germline mutations in DNA mismatch repair genes, including the MSH2 gene. We analysed an MFH diagnosed in a 45-year-old male HNPCC patient carrying a germline MSH2 mutation for HNPCC-associated molecular characteristics, to investigate a possible relationship between the tumour and that mutation. DNA analysis revealed microsatellite instability and loss of one MSH2 copy, and immunohistochemistry showed absence of nuclear MSH2 protein staining. To investigate whether this is a common finding in MFH, microsatellite instability and nuclear MSH2 protein staining was tested for in 5 and 6 sporadic MFHs, respectively. None showed microsatellite instability and all stained positively for MSH2. Together, these findings show that in rare cases, MFH may be part of the HNPCC tumour spectrum.

Primary giant cell malignant fibrous histocytoma of the lung: a case report

A rare case of malignant fibrous histiocytoma of giant cell type originating in the lung of a 46-year-old woman is presented. The patient complained of having a cough that had lasted for a few weeks. A chest X-ray photograph showed a tumor shadow on the left lung. Histological and cytological examination of the biopsy specimen revealed that the tumor was a kind of sarcoma. An operative procedure was selected because of tumor invasion into the trunk of the left pulmonary artery, which was discovered on computed tomography examination, and because metastatic tumor was excluded clinically. The tumor was almost encapsulated and 6 x 6 x 6 cm in size; however, it also showed invasion into the pulmonary artery and bronchial lumen. A histological survey of the tumor showed a wide range of patterns such as fibrous, pleomorphic, fascicular and osteoclast-like giant cell figures; however, the osteoclast-like giant cell area was predominant. Immunohistochemically, the tumor cells were positive for vimentin, CD68 for histiocytic marker and alpha1-antichymotrypsin, and negative for keratin, epithelial membrane antigen, S-100 protein, MT-1, desmin, myoglobin and lysosome. No primary tumor was found clinically in any part of the patient's body at 2 and 4 months after operation. Consequently, she was diagnosed as having primary giant cell malignant fibrous histiocytoma of the lung.