Besides conventional chondrosarcoma, several rare chondrosarcoma subtypes are described, comprising about 15% of all chondrosarcomas. Clear cell chondrosarcoma (CCS) is a low-grade malignant tumour, often recurring after curettage, and showing overall survival of about 85%. Mesenchymal chondrosarcoma (MCS) is a highly malignant tumour occurring in bone and soft tissue of relatively young patients. The tumour shows differentiated cartilage mixed with undifferentiated small round cells. It often metastasises and shows a 5-year overall survival of 55%. Dedifferentiated chondrosarcoma (DDCS) is a tumour containing a high-grade non-cartilaginous sarcoma (DD), and a usually low-grade malignant cartilage-forming tumour (WD).

The prognosis is poor. The lack of efficacious treatment of these rare tumours emphasises the need to learn more about their characteristics and to unravel potential targets for therapy.

We constructed tissue microarrays (TMAs) with 2mm cores of 45 DDCS (WD and DD), 24 CCS, and 25 MCS, in triplicate.

Using immunohistochemistry, we investigated protein expression of estrogen-signaling molecules, growth plate-signaling molecules, and other molecules which might be potential targets for therapy. In addition, we gathered genomic information using Agilent 44K oligo arrays.

30% of the WD components were positive for Cox-2. Almost all others were negative. For Bcl2, 88% of the small cells and 32% of the cartilage in MCS were positive. In CCS, WD, and DD 48%, 4%, and 12% were positive, respectively. We demonstrated the presence of ESR1 and aromatase protein in the majority of tumours in all subtypes. Using array CGH, we observed similar aberrations in the two components of DDCS, with additional aberrations in the DD.

Celecoxib treatment is not recommended, as most of the tumours are negative for Cox-2. However, the presence of ESR1 and aromatase support a possible effect of anti-estrogen treatment in all subtypes, and application of Bcl2 inhibitors might chemosensitise MCS.

Chondrosarcomas are notorious for their resistance to conventional chemo- and radiotherapy, indicating there are no curative treatment possibilities for patients with inoperable or metastatic disease. We therefore explored the existence of molecular targets for systemic treatment of chondrosarcoma using kinome profiling.

Peptide array was performed for 4 chondrosarcoma cell lines and 9 primary chondrosarcoma cultures. Acitivity of kinases was verified using immunoblot and active Src- and PDGFR signaling were further explored using imatinib and dasatinib on chondrosarcoma cell lines and primary cultures.

The AKT1/GSK3B pathway was clearly active in chondrosarcoma. In addition, the PDGFR pathway and the Src kinase family were active. PDGFR and Src kinases can be inhibited by imatinib and dasatinib, respectively. While imatinib did not show any effect on chondrosarcoma cell cultures, dasatinib showed a decrease in cell viability at nanomolar concentrations in 3 out of 5 chondrosarcoma cultures. Whereas inhibition of phosphorylated Src (Y419) was found both in responsive and non-responsive cells, caspase-3 related apoptosis was found only in cell line GIST882, suggesting that the mechanism of decreased cell viability in chondrosarcoma by dasatinib is caspase-3 independent.

In conclusion, using kinome profiling we found the Src pathway to be active in chondrosarcoma. Moreover, in the chondrosarcoma cell lines and primary cultures we showed that the inhibitor of the Src pathway, dasatinib, may provide a potential therapeutic benefit for chondrosarcoma patients which are not eligible for surgery.

High-grade angiosarcomas (HGAS) of bone are rare and represent less than 1% of the primary malignant bone tumours. Because of their rareness little is known. Clinically, it is accepted that they are extremely aggressive. Due to the lack of uniform terminology and accepted histological criteria, terminology and classification of primary malignant vascular tumours of bone has been highly controversial. Today, angiosarcoma is the most accepted term for high-grade primary vascular tumour of bone, recognized by the 2002 WHO Classification. However, distinct histological hallmarks to define a HGAS of bone are not clear.

We collected 64 HGAS of bone diagnosed between 1964 and 2007 from the files of the departments of pathology, Leiden University Medical Center (Leiden), Rizzoli Institute (Bologna) and University Hospitals (Leuven). All clinical, radiological, and pathological data were reviewed and different histological criteria were scored. A tissue micro-array was constructed containing 57 HGAS of bone. To confirm the vascular origin of all lesions and to investigate the diagnostic value of commonly used markers, immunohistochemistry was performed for CD31, CD34, Factor VIII, and keratin AE1/AE3. Staining was evaluated positive or negative.

Among 64 patients with HGAS of bone, there are 41 males and 23 females. There is a wide age distribution, with a nearly equal distribution from the second to the sixth decade. The solitary cases are mostly located in the extremities (66%) followed by trunk (12.8%), axial/central location (10.6%) and pelvis (10.6%). 17 cases (73%) have multifocal bone lesions. HGAS of bone show variable histological patterns. Association with clinical outcome (chi-square test) reveals that there is a significant poor survival when the tumour has tree or more mitoses (p=0.001), a macronucleoli (p=0.011) or there is an absence of an eosinophilic infiltrate (p=0.023). The HGAS of bone are positive for CD31 in 53/55 (96%), CD34 in 33/57 (58%), Factor VIII in 47/55 (86%), and keratin in 40/57 (70%). Only 15 out of 40 (38%) keratin positive angiosarcomas, showed an epithelioid phenotype at classical morphology. All tumours with an epithelioid phenotype are keratin positive.

Although HGAS of bone in general have a poor outcome, histological criteria such as three or more mitoses, the presence of a macronucleolus and the absence of an eosinophilic infiltrate can be useful to predict a more aggressive course, consistent with the clinical behaviour of a high-grade angiosarcoma. CD31 and Factor VIII are the best diagnostic markers for HGAS of bone. It is striking that keratin positivity is seen in the majority of cases, and is independent of epithelioid morphology. Pathologists should be aware of this to avoid misinterpretation as metastatic carcinoma.

Haemangiopericytoma (HPC) was first described by Murray and Stout as a soft tissue neoplasm with distinct morphologic features, presumably composed of pericytes. Over the years, it became clear that many tumours could mimic a HPC-like pattern. These days, it is accepted that in soft tissue most lesions diagnosed as HPC in the past are actually solitary fibrous tumours (SFT), synovial sarcomas (SS) or myofibromatoses. It has been unclear whether the very rare HPC of bone is atrue entity, or that the HPC-like vessels are non-specific and part of other, different entities.

We collected 10 primary HPC of bone from four institutions diagnosed between 1952 and 2002. All data were reviewed. Immunohistochemistry was performed for CD31, CD34, factor VIII, SMA, keratin AE1/AE3 and EMA. Staining was evaluated as focal positive, diffuse positive or negative.

There were five female and five male patients between 21 and 73 years of age (mean 45.3 y). All tumors were located within bone. The primary site of the tumour was the femur in two patients, humerus in one, fibula in one, sacrum in two and vertebra in three. All tumours showed the presence of prominent thin-walled branching vessels surrounded by more undifferentiated spindle or round cells. However these cells showed some variation in their morphologic pattern: five tumours showed a patternless architecture and varying cellularity, consistent with SFT. Three tumours showed more densely packed sheets of poorly differentiated cells, similar to SS, and one case each represented paraganglioma and PEComa, possibly metastatic. Tumours resembling SFT showed usually focal to diffuse staining for CD34. All tumours were negative for SMA. Two tumours more similar to SS showed focal positive staining for keratin AE1/AE3 or EMA (66%). Some tumours showed severe decalcification artefact. None of the 10 tumours show CD31 and factor VIII expression. FISH is performed to study SYT rearrangements.

Our retrospective review of tumours diagnosed as HPC of bone in the past revealed the absence of true pericytic differentiation and the existence of both SFT of bone and SS of bone. Therefore, as in soft tissue tumours, HPC-like features are non specific. Diffuse CD34 staining is helpful to diagnose SFT of bone, whereas keratin/EMA staining is suggestive for SS of bone.

Enchondromatosis is a non-hereditary disease, characterised by the presence of multiple enchondromas. While Ollier Disease is typified by multiple enchondromas, in Maffucci Syndrome they are combined with haemangioma.

Due to the rarity of these diseases, systematic studies on clinical behaviour providing information how to treat patients are lacking.

This study intends to answer the following questions: What are predictive factors for developing chondrosarcoma? When is extensive surgery necessary? How often patients die due to dedifferentiation or metastasis?

Twelve institutes in eight countries participated in this descriptive retrospective EMSOS-study. 118 Patients with Ollier Disease and 15 patients with Maffucci Syndrome were included. Unilateral localization of disease was found in 60% of Ollier patients and 40% of patients with Maffucci Syndrome.

One of the predictive factors for developing chondrosarcoma is the location of the enchondromas; the risk increases especially when enchondromas are located in the scapula (33%), humerus (18%), pelvis (26%) or femur (15%). For the phalanges, this risk is 14% in the hand and 16% in the feet. The decision whether or not to perform extensive surgery is difficult, especially in patients who suffer multiple chondrosarcomas.

Malignant transformation was found in fourty-four patients with Ollier Disease (37%) and eight patients with Maffucci Syndrome (53%). Multiple synchronous or metachronous chondrosarcomas were found in 15 patients.

Nine patients died (range 21–54 yrs). Seven of them died disease related due to pulmonary metastasis (2 humerus, 2 pelvis, 3 femur). Two patients died from glioma of the brain.

In conclusion, one important predictive factor for developing chondrosarcoma is the location of the enchondromas; interestingly, only patients with chondrosarcoma outside the small bones died of their disease. In this series, no dedifferentiation of chondrosarcoma was seen. A first design flow-chart how to approach chondrosarcoma in patients with Ollier Disease and Maffucci Syndrome is in preparation.

In both Enchondromatosis (EC) and Multiple Osteochondromas (MO), multiple benign cartilaginous tumours occur, which have a severely increased risk of malignant progression. Preventing new tumor formation and malignant progression would benefit the prognosis of these patients. A protective effect of selective Cox-2 inhibitor celecoxib, has been suggested against development and growth of colorectal cancer in familial syndromes. At last year’s EMSOS meeting we reported on expression of Cox-2 in 37% (central) – 46% (peripheral) of conventional chondrosarcomas. mRNA levels of EC related tumours were slightly higher than the solitary tumours. Celecoxib treatment of the chondrosarcoma cell lines resulted in a 3 fold decrease of PGE2 levels already at 5 μM. A significant decrease in proliferation was found at 10 μM in OUMS27 and at 25 μM in SW1353 and CH2879 compared to DMSO controls.

For the present study we assessed the (prophylactic) effect of celecoxib on chondrosarcoma growth in vivo using a xenograft model of immunoincompetent nude mice which were injected with cell line CH2879 subcutaneously. Tumour volume was measured during 8 weeks. Celecoxib serum levels were determined by HPLC. Expression of proliferation marker Ki-67 and Cox-2 was assessed by IHC.

Our in vivo results also showed a beneficial effect of high dose prophylactic celecoxib treatment. Tumour volumes were negatively correlated with celecoxib serum levels (r2=0.152). However, at the end of pubertal growth of the mice, a catch-up tumour growth was observed, resulting in the absence of differences in tumour volume between control and treatment groups. Accordingly, proliferation marker Ki67 was higher expressed in the treated groups at sacrifice.

This suggests that there is no role for celecoxib in the treatment of adult chondrosarcoma patients. Celecoxib treatment of younger patients, especially to prevent formation of new tumours in EC and OC patients, might be beneficial, however more research is necessary.