Biology and management of clear cell sarcoma: state of the art and future perspectives

INTRODUCTION

Clear cell sarcoma (CCS) is an aggressive tumor, typically developing in tendons or aponeuroses. The outcome of this orphan disease is poor, with 5-year and 10-year survival rates of localized CCS around 60-70% and 40-50%. Once the disease has metastasized, it is usually fatal due to its chemotherapy-resistant nature. Systemic treatment options are poorly standardized and the use of chemotherapy is based on weak scientific evidence.

AREAS COVERED

In this review, we systematically discuss the current scientific evidence for the systemic treatment of CCS, including tyrosine kinase inhibitors, immunotherapy and MET inhibitors. Expert commentary: Recent insights in the biology of CCS have identified new potential therapeutic targets, which should be tested in prospective clinical trials. Whenever possible, patients with metastatic CCS should be included in clinical trials with good biological rationale. Innovative trial methodology and new regulatory mechanisms are required to provide patients with uncommon cancers with active drugs.

BRAF and NRAS mutations are uncommon in melanomas arising in diverse internal organs

BACKGROUND

Malignant melanoma arising from different body compartments may be associated with differing aetiological factors and clinical behaviour, and may manifest diverse molecular genetic profiles. Although many studies have focused on cutaneous melanoma, little is known of mucosal and other types of melanoma. In particular, malignant melanoma of soft parts is different from other melanomas in many respects, yet manifests a common melanocytic differentiation. Mutation of BRAF is now known to be common in cutaneous melanomas, and raises possible new therapeutic options of anti-RAF treatment for these patients. Few data are available for non-cutaneous melanomas.

AIMS

To study the incidence of BRAF and NRAS mutations in melanomas arising in diverse internal organs.

METHODS

Fifty one melanomas from various internal organs were investigated for BRAF and NRAS mutation by direct DNA sequencing.

RESULTS

BRAF and NRAS mutations were found in two and five mucosal melanomas arising from the aerodigestive and female genital tracts (n = 36). Their occurrence is mutually exclusive, giving a combined mutation incidence rate of 19.4% in mucosal melanomas. Both BRAF and NRAS mutations were absent in malignant melanoma of soft parts (n = 7). BRAF mutation was also absent in uveal melanoma (n = 6), but was seen in two of five cutaneous melanomas. The incidence of BRAF or combined BRAF/NRAS mutations in all non-cutaneous groups was significantly lower than published rates for cutaneous melanomas.

CONCLUSION

Each melanoma subtype may have a unique oncogenetic pathway of tumour development, and only a small fraction of non-cutaneous melanomas may benefit from anti-RAF treatment.

Malignant melanoma is genetically distinct from clear cell sarcoma of tendons and aponeurosis (malignant melanoma of soft parts)

Clear cell sarcoma of tendons and aponeuroses (malignant melanoma of soft parts) and conventional malignant melanoma may demonstrate significant morphologic overlap at the light microscopic and ultrastructural level. Consequently, the clinically relevant distinction between primary clear cell sarcoma and metastatic melanoma in the absence of a known primary cutaneous, mucosal or ocular tumour may occasionally cause diagnostic problems. A balanced translocation, t(12;22)(q13;q13), which can be detected, amongst others, using the reverse transcriptase polymerase chain reaction (RT-PCR) or fluorescent in situ hybridization (FISH), has been identified in a high percentage (50-75%) of clear cell sarcomas and is presumed to be tumour specific. Whether this chromosomal rearrangement is present in malignant melanoma has, to date, not as yet been studied by molecular genetic or molecular cytogenetic techniques. Using RT-PCR and FISH, a series of metastases from 25 known cutaneous melanomas and 8 melanoma cell lines (5 uveal and 3 cutaneous) were screened for the t(12;22)(q13;q13) translocation. Primers for RT-PCR were chosen based upon published breakpoint sequences. The Cosmids G9 and CCS2.2, corresponding to the 5' region of EWS and 3' region of ATF-1 respectively, were used as probes. The translocation was not identified in any of the melanomas or melanoma cell lines analysed in this study; in contrast this translocation was identified in 3 out of 5 clear cell sarcomas using these techniques. This allows distinction between translocation positive cases of clear cell sarcoma and malignant melanoma at a molecular genetic level. Consequently, in diagnostically challenging cases, this represents a valuable tool for the clinicopathologic differentiation between these two entities, with an important impact on patient management and prognosis.