Distribution and prognostic significance of human telomerase reverse transcriptase (hTERT) expression in giant-cell tumor of bone.

Giant-cell tumor of bone is considered a benign, locally aggressive and rarely metastasizing neoplasm of bone. Specific microscopic or radiographic findings that reliably predict behavior have remained elusive. However, recent evidence suggests that activity of the telomerase enzyme complex correlates with recurrence in giant-cell tumor, although the subset of cells with telomerase activity in these heterogeneous tumors has not been defined. In the present study, we investigated whether immunostaining for human telomerase reverse transcriptase, a component of the telomerase complex, correlates with outcome in giant-cell tumor and the distribution of telomerase reverse transcriptase staining in these tumors. We analyzed 58 cases of giant-cell tumor for the presence and pattern of telomerase reverse transcriptase immunostaining, presence of soft tissue involvement and the type of initial surgery, and correlated these findings with recurrence-free survival and metastasis-free survival. Specific staining with telomerase reverse transcriptase was present in 20 out of 58 tumors (35%) in the nuclei of mononuclear cells and, occasionally, osteoclast-like giant cells. Furthermore, positive telomerase reverse transcriptase immunohistochemistry correlated with recurrence-free survival (P=0.02), whereas the presence of soft tissue extension (P=0.3) and the type of initial surgery (P=0.2) did not. Only soft-tissue extension significantly correlated with metastasis-free survival (P=0.003). Therefore, telomerase reverse transcriptase expression may predict recurrence in giant-cell tumor insofar as positive immunostaining correlates with shorter recurrence-free survival and may be a useful prognostic marker to stratify patients to more aggressive treatment protocols.

Beta-catenin nuclear expression correlates with cyclin D1 expression in primary and metastatic synovial sarcoma: a tissue microarray study.

CONTEXT: The association between aberrant (nuclear) beta-catenin expression and cyclin D1 accumulation has been demonstrated in diverse neoplasms. In synovial sarcoma (SS), aberrant beta-catenin expression has prognostic relevance, but the association with cyclin D1 has not been established. The SYT-SSX fusion protein, unique to SS, may independently increase cyclin D1. OBJECTIVE: To determine whether nuclear beta-catenin is associated with cyclin D1 overexpression in SS and whether primary and metastatic SS differ in the expression of these markers. DESIGN: We incorporated 82 tumors initially diagnosed as SS into a tissue array. Fluorescence in situ hybridization with custom probes was used to select t(X;18) positive tumors. Clinical data, tumor type and outcome were tabulated. The tumors were tested for the association between nuclear beta-catenin and cyclin D1 immunostaining. Primary and metastatic tumors were compared. RESULTS: Fifty-one tumors (41 primary and 10 metastatic) from 43 patients demonstrated t(X;18). Cyclin D1 staining was identified in 21 (59%) primary and 8 (80%) metastatic tumors, respectively, and nuclear beta-catenin in 24 (41%) primary and 7 (70%) metastatic tumors, respectively. No significant difference was noted between primary and metastatic tumors with respect to the above markers. The presence of nuclear beta-catenin showed a significant association with cyclin D1 expression (P < .001). A small number of cyclin D1 cases were negative for nuclear beta-catenin but positive for phosphorylated Akt. CONCLUSIONS: Increased cyclin D1 in SS may be driven by abnormally expressed beta-catenin, similar to other neoplasms. The pattern of expression of these markers is established early during tumorigenesis.

Mismatch repair protein expression and microsatellite instability: a comparison of clear cell sarcoma of soft parts and metastatic melanoma.

Clear cell sarcoma of soft parts is a rare soft tissue malignancy that shows phenotypic overlap with cutaneous melanoma but can be distinguished by the presence of a t(12;22) translocation. Microsatellite instability (MSI), a variation in the lengths of short repeat DNA segments in the genome, has been implicated in melanoma tumorigenesis, but is rare or absent in clear cell sarcoma. Defects in the mismatch repair (MMR) enzyme complex correlate with MSI in some tumor types, allowing the use of immunohistochemistry for the MMR proteins hMLH1 and hMSH2 to predict the presence of MSI. To determine if the association between MMR defects and MSI extends to clear cell sarcoma, we compared a group of nine clear cell sarcomas to 11 metastatic melanomas on the basis of MSI and the expression of MMR proteins. MSI was studied using fluorescence-based multiplexed PCR of five loci. Immunohistochemistry was evaluated on formalin-fixed paraffin-embedded tissue for hMLH1, hMHS2 and hMSH6. MSI was present in only 1/9 (11%) clear cell sarcoma case and in 8/11 (73%) melanoma cases. Immunostaining for hMLH1 and hMSH2 was preserved in all the clear cell sarcomas but loss of immunostaining for one or both proteins was seen in 6/11 melanomas (55%). hMSH6 was detected in 7/9 (78%) clear cell sarcomas and 10/11 (91%) of melanomas. Clear cell sarcoma and metastatic melanoma differed significantly with respect to the presence of MSI (P=0.010) and staining for hMLH1 and/or hMSH2 (P=0.014) but not hMSH6 (P=0.57). Mismatch repair, and consequently genomic instability may contribute to tumorigenesis in melanoma but not clear cell sarcoma. Immunostaining for hMLH1 and hMSH2 and MSI analysis may be helpful in the differential diagnosis of large soft tissue or visceral malignancies with melanocytic differentiation.

Utility of CD117 immunoreactivity in differentiating metastatic melanoma from clear cell sarcoma.

CONTEXT: Clear cell sarcoma is a malignant soft tissue tumor with melanocytic differentiation. Molecular methods are sometimes necessary to identify the unique t(12; 22)(q13;q12) translocation and differentiate clear cell sarcoma from melanoma. OBJECTIVE: To determine whether CD117 immunoreactivity may be useful in separating melanoma from clear cell sarcoma. DESIGN: We identified 20 tumors listed in our surgical pathology files that were diagnosed as clear cell sarcoma or in which clear cell sarcoma was strongly considered. These were tested for the presence of the t(12;22) translocation by reverse transcriptase/polymerase chain reaction and sequencing from paraffin-embedded tissue. Tumors with a t(12;22) translocation were immunostained with an antibody to CD117 and compared with 16 similarly stained metastatic melanomas. RESULTS: Twelve tumors from 9 patients demonstrated t(12;22). No metastatic melanomas demonstrated t(12;22). None of the 12 clear cell sarcomas showed membrane or cytoplasmic staining for CD117. Conversely, 10 (63%) of 16 metastatic melanomas were, at least focally, positive for CD117; this difference was significant (P < .001). Interestingly, 3 tumors in which clear cell sarcoma was initially considered as a diagnosis, but which lacked t(12;22), were also positive for CD117. CONCLUSIONS: Reverse transcriptase/polymerase chain reaction, performed on paraffin-embedded tissue, is a useful, rapid tool for identifying the presence of t(12;22) in clear cell sarcoma. The CD117 immunoreactivity may prove useful in the differential diagnosis of deep soft tissue or visceral lesions with melanocytic differentiation; positive staining results exclude clear cell sarcoma, but are compatible with metastatic melanoma.

c-Kit is not expressed in malignant mesothelioma.

Overexpression of KIT protein (CD117), the product of the c-kit gene, has been shown to have important prognostic and therapeutic implications for a number of malignant neoplasms. Previous studies have shown conflicting results regarding the expression of c-kit in malignant mesothelioma. To determine whether malignant mesothelioma expresses KIT, immunohistochemistry and RT-PCR were used to analyze archived tissue from 37 cases of mesothelioma. Although a subset of mesotheliomas demonstrated specific staining with the DAKO anti-KIT antibody, in each case staining was nuclear. We could not detect c-kit mRNA by a sensitive RT-PCR assay, even in cases with strong nuclear staining. Furthermore, a second anti-KIT antibody (Cell-Marque) only demonstrated staining in a single mesothelioma case and in none of the cases that demonstrated nuclear staining. We conclude that immunoreactivity for KIT in mesothelioma does not represent expression of the c-kit gene and may represent antibody cross-reaction with nuclear proteins. Our results raise doubt about previously reported expression of KIT in mesothelioma and consequently, the applicability of therapeutic agents that target the kinase activity of KIT.

Malignant mesothelioma does not demonstrate overexpression or gene amplification despite cytoplasmic immunohistochemical staining for c-Erb-B2.

BACKGROUND: Previous studies have shown conflicting results regarding the expression of c-Erb-B2 in malignant mesothelioma. Overexpression of the c-erb-B2 gene product in a subset of mesothelioma may have prognostic or therapeutic implications. OBJECTIVE: To determine whether malignant mesothelioma demonstrates c-Erb-B2 overexpression and, if so, whether such overexpression correlates with gene amplification. METHODS: Immunohistochemistry, reverse transcription-polymerase chain reaction, and fluorescent in situ hybridization were used to analyze archived tissue from 37 cases of malignant mesothelioma. RESULTS: Although immunohistochemical staining for c-Erb-B2 was detected in most mesotheliomas, the staining was cytoplasmic and was not consistent between the 2 different primary antibodies used. Moreover, even cases with strong cytoplasmic staining for c-Erb-B2 did not demonstrate increased messenger RNA levels or gene copy numbers compared to cases that demonstrated no staining. CONCLUSIONS: Cytoplasmic immunoreactivity for c-Erb-B2 in mesothelioma does not represent gene overexpression or amplification and may be an immunohistochemical artifact.