[Hereditary bone tumors]

[Hereditary bone tumors]

Hereditary bone tumors are rare and result from mutations affecting cell cycle regulation (e.g. retinoblastoma syndrome/RB1 and Li-Fraumeni syndrome/TP53, Gardner syndrome/APC), energy metabolism (enchondromatosis/IDH1/2), complex signaling cascades (multiple hereditary exostoses/EXT1/2) and DNA integrity (Rothmund-Thomson/RECQL4, Werner/WRN and Bloom syndromes/BLM). The majority of syndromes are incompletely understood and can lead to multiple benign tumors, of which some might undergo secondary malignant transformation over time (enchondromatosis: enchondromas, multiple hereditary exostoses: osteochondromas, Gardner syndrome: osteomas) or bone sarcomas, primarily osteosarcomas as primary (Li-Fraumeni, Rothmund-Thomson, Werner and Bloom syndromes) or secondary manifestation (retinoblastoma syndrome) of the disease. Some syndromes additionally predispose to the development of a variety of other malignant tumors during life. Compared to sporadically occurring tumors, syndrome-related neoplasms can differ in the time of manifestation, site and histology, which can help in recognizing a specific tumor predisposition syndrome.

[The clonal evolution of osteosarcomas]

Osteosarcomas are highly aggressive bone tumors that mainly occur in the metaphyses of long bones in children and adolescents. Genetically, they are characterized by complex structural and numerical aberrations with large intra- and interindividual variations which hamper the identification of the initiating and driving events. Sequencing and copy number analyses in a study of 123 pretherapeutic osteosarcoma samples identified mutations in 14 genes as the potential main drivers. Although almost half of all osteosarcomas could be attributed to mutations in TP53 and RB1, no single driver gene could be found that was clearly responsible for the majority of tumors. There were also no unequivocal correlations between single aberrations and clinicopathological parameters; however, when looking at the mutation signatures, a striking resemblance to BRCA-deficient breast cancer was evident in the majority of osteosarcoma profiles. We therefore focused our interest on genes involved in homologous recombination repair and applied different algorithms that have been shown in the literature to be indicators for functional impairment in these signaling cascades. Indeed, >80 % of osteosarcomas showed signatures similar to BRCA-deficient tumors and in osteosarcoma cell lines a response to poly(ADP-ribose) polymerase (PARP) inhibitors could be demonstrated. Our findings thus imply that multiple oncogenic pathways can converge and lead to chromosomal instability during osteosarcoma evolution resulting in the acquisition of BRCA-like traits, which might be of potential therapeutic relevance.

Bilateral Scapulothoracic Osteochondromas in a Patient With Hereditary Multiple Exostosis: A Case Report and Review of the Literature

Hereditary multiple exostosis (HME) is an autosomal dominant disorder characterized by two or more benign growing, cartilage capped tumors of long bones called osteochondromas. If abnormal growth and clinical symptoms of osteochondromas newly appear in adults, malignant transformation of the usually benign growing tumors should be suspected and diagnostic testing should be initiated. Against the background of hypothesized higher malignant transformation of osteochondromas into chondrosarcoma in individuals with shoulder exostoses, we report a case of bilateral scapulothoracic osteochondromas in a patient suffering from HME. A 60-year-old female with HME complained of chest pain while being hospitalized for bilateral femoral fractures. A computed tomography scan of the chest was performed to rule out pulmonary embolism. However, bilateral osteochondromas in the scapulothoracic spaces were detected. Due to absence of radiographic evidences for malignant transformation in the patient, invasive diagnostic procedures such as biopsy and histological examination were recommended in order to exclude malignant transformation of both osteochondromas. Physicians should be aware that patients with HME who present with shoulder pain should be examined for osteochondromas in the scapulothoracic space. Due to possible sarcomatous transformation, regular follow-ups are necessary for adolescents and adults.

[Osteochondroma and multiple osteochondromas: recommendations on the diagnostics and follow-up with special consideration to the occurrence of secondary chondrosarcoma]

PURPOSE

Osteochondroma represents the most common form of benign bone tumor. Clinical manifestations include deformity of bone, compression of surrounding tissue and vascular or neurological compromise. Osteochondromas may be solitary (solitary osteochondroma, SO) or multiple (multiple osteochondromas MO). Recurrence after surgery is a known problem especially in MO and malignant transformation is rare but more common in MO than in solitary cases. Reliable recommendations regarding diagnostics and clinical follow-up are currently lacking.

PATIENTS AND METHODS

A comprehensive literature review and a review of own patient files with SO/MO treated between 2000 and 2011 in this hospital were performed. The age of patients at diagnosis, tumor localization, clinical aspects, recurrence and the risk of malignant transformation in secondary (i.e. epiexostotic) chondrosarcoma were analyzed. The follow-up including patients who received surgery ranged between 2 and 127 months for patients with SO and between 2 and 84 months for MO.

RESULTS

A total of 39 patients with SO from this hospital were included in the study. Out of 36 patients who received surgery 3 recurrences were registered after an average time of 62 months. In addition, 11 patients with MO were identified and all received surgery. In 5 out of 11 cases recurrences occurred after an average time of 20.6 months. Secondary chondrosarcomas were not recorded in this series. According to the literature an increased risk of malignant transformation was found for osteochondromas of the axial skeleton, in the proximal aspect of the extremities, as well as for recurrent tumors and for MO. Pain and/or increase in size of lesions after skeletal maturation were the most common clinical signs of transformation. There was a wide time interval between the initial diagnosis and the development of secondary chondrosarcoma. In MO secondary chondrosarcoma has been described before skeletal maturity.

CONCLUSIONS

The risk of malignant transformation of SO is generally low. Axial lesions as well as recurrent osteochondromas and MO seem to have an increased risk of malignant transformation. The follow-up, requiring sufficient primary diagnostics, includes regular self-control and can usually be clinically carried out in more peripherally located lesions but in certain cases supplementary X-ray imaging is needed. In cases of anatomical regions which are more difficult to access manually, follow-up examination by magnetic resonance imaging (MRI) is the method of choice. Especially MO patients seem to benefit from long-term follow-up: when the tumor is located in the trunk and in (proximal) long bones MRI or whole-body MRI, respectively, should be performed once a year after skeletal maturity because of the higher risk of malignant transformation in these patients.