Immunohistochemical KIT (CD117) expression in thymic epithelial tumors

Japan Research Institute, Edo, Tōkyō, Japan
Chest (Impact Factor: 7.48). 08/2005; 128(1):140-4. DOI: 10.1378/chest.128.1.140
Source: PubMed


It is sometimes very difficult both clinically and pathologically to distinguish thymic epithelial tumors from primary lung carcinoma with massive anterior mediastinal involvement. The expression of KIT (CD117) in thymic epithelial tumors was investigated in order to evaluate its usefulness as a marker supporting differential diagnosis and choice of therapy.
We examined the immunohistochemical expression of KIT in 70 resected thymic epithelial tumors (thymomas, 50; thymic carcinomas, 20) that had been reclassified on the basis of the World Health Organization histologic classification system. We also compared the expression of KIT and CD5 in 20 thymic carcinomas with their expression in 20 resected pulmonary squamous cell carcinomas that were spreading directly into the mediastinum.
Of the 50 thymomas, only 2 (4%) showed positive immunoreactivity for KIT (type A thymoma, 1; type B3 thymoma, 1), whereas 16 of the 20 thymic carcinomas (80%) showed positive immunoreactivity. Testing was positive for CD5 in 14 of the 20 thymic carcinomas (70%). In the pulmonary squamous cell carcinomas, in contrast, the immunohistochemical expression of KIT and CD5 was found in only 4 of 20 carcinomas (20%) and 3 of 20 carcinomas (15%), respectively. Furthermore, of the 40 specimens examined (either thymic or lung carcinoma) all 13 that were positive for both KIT and CD5 were thymic carcinomas, and 13 of the 16 that were negative for both were lung carcinomas.
KIT expression is a useful immunohistochemical marker for the diagnosis of thymic carcinoma, and its examination in combination with CD5 immunohistochemistry would greatly help in the differential diagnosis of primary thymic carcinoma from pulmonary squamous cell carcinoma. Further investigations at a genetic level should be encouraged, not only to define the role of KIT in the oncogenesis of thymic epithelial tumors, but also to establish target-based therapy.

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    • "However, their description of multiple mitotic figures and of necrosis occurring in EC in lymph nodes might better correspond to TC cases. By immunophenotyping of our cases, neither CD5 surface molecule, typically expressed by TC, mainly of squamous cell type [13–15], nor CD117, a useful TC marker [16, 17], was found to be expressed. A differential diagnosis of thymoma metastasis versus lymph node involvement by T-lymphoblastic lymphoma was considered for Cases 2 and 3: MIC-2 antibody (CD99) and TdT proved useful in assessing an immature phenotype of lymphocytes present in lymph node metastases, while the anti-CK 19 staining was useful in confirming the epithelial nature of the metastatic lymph node infiltration. "
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    ABSTRACT: Aim: The purpose of the present study was to characterize the morphological features of thymoma metastases in lymph nodes and to evaluate the possibility of their subtyping according to the 2004 WHO classification of thymus tumors. Materials and methods: We reviewed 210 thymoma cases in our series of thymic epithelial tumors (TET), including their recurrences and lymphogenous metastases. Three cases of lymph node metastases, one case occurring synchronously with the primary tumor and one synchronously with the first relapse (both in intrathoracic location) and one case of metastasis observed in a laterocervical lymph node subsequently to two thymoma relapses were found. Results: The metastatic nodes were variably but extensively involved in all cases. The histological features were similar in both primary tumors and metastases. Thymoma metastases were subtyped according to the WHO classification as B3 (one case) and B2 (two cases), and distinctive features in comparison to metastatic epithelial neoplasias from other sites were observed. Conclusion: Thymoma lymph node metastases, although rare, can be subtyped according to the WHO classification on the basis of their morphological and immunohistochemical features. Clinically, the presence of nodal metastases may herald subsequent relapses and further metastases even in extrathoracic sites.
    BioMed Research International 07/2014; 2014:546149. DOI:10.1155/2014/546149 · 2.71 Impact Factor
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    • "Multiple oncogenes and tumor suppressor genes have been found correlated to oncogenesis, development and metastasis of thymic epithelial tumors (TET) [3]. STAT3, one of transcription factors under recent vigorous researches, is considered as an oncogene correlated closely to proliferation, differentiation, cellular apoptosis, immune escape, vascularization, invasion and metastasis in multiple malignancies [4]. "
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    ABSTRACT: Background More and more evidences demonstrate the significance of Signal transducers and activators of transcription 3(STAT3) in oncogenesis and tumor development. However, little systematic researches have been reported on the correlation between STAT3 and thymic epithelial tumor (TET). Methods Expression of STAT3 protein in 80 thymic epithelial tumors was detected by immunohistochemistry (IHC). The difference of STAT3 expression was compared by the χ2 test. Estimation of survival was calculated using the Kaplan-Meier method, and the statistical differences were analyzed using the Log-rank test. Results Positive expression of STAT3 protein was significantly associated with Masaoka staging and WHO histological classification (P < 0.05), but not with age, gender, or tumor size. The rate of postoperative recurrence/metastasis was 33.33% in STAT3-positive tumors, compared with 4.55% in negative ones (P < 0.05). 5-year survival was significantly lower in STAT3-positive subjects (61.11%) than in negative ones (97.73%) (P < 0.01); In patients in Masaoka stage III or IV and WHO B3 or C, 5-year survival rate of subjects positive in STAT3 (35.00%, 35.00%) was statistically lower than that of the negative ones (92.31%, 91.67%). Cox regression analysis revealed that positive expression of STAT3 protein was an independent prognostic factor of thymic epithelial tumors (HR = 9.325, P = 0.044). Conclusion Positive expression of STAT3 protein increases along with the rising malignant degree of thymic epithelial tumors. It may be considered as an independent prognostic parameter with good prognostic value to evaluate the possibility of recurrence/metastasis in patients with thymic epithelial tumor.
    Journal of Cardiothoracic Surgery 04/2013; 8(1):92. DOI:10.1186/1749-8090-8-92 · 1.03 Impact Factor
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    • "Imatinib is a tyrosine kinase inhibitor (TKI) targeting predominantly Abelson cytoplasmic tyrosine kinase, (abl ) platelet-derived growth factor receptor (PDGFR), and c-KIT. C-KIT (CD117) overexpression is quite common in thymic carcinomas (~80%), but it is rare in thymomas (~4%).28 The tumor of the patient in the aforementioned imatinib case report did indeed demonstrate overexpression of KIT. "
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    ABSTRACT: The purpose of this review article is to review recent advances in the treatment of advanced thymic epithelial tumors. These tumors are generally responsive to cytotoxic combination chemotherapy in the first-line setting. While newer agents have shown efficacy in the salvage setting, there is no one standard approach. A multitude of targeted agents have shown promise generally in case reports, though as of yet, nothing has shown consistent benefit. Because of the rarity of thymic epithelial tumors, clinical trial enrollment is difficult but nevertheless essential.
    OncoTargets and Therapy 09/2012; 5:177-84. DOI:10.2147/OTT.S23267 · 2.31 Impact Factor
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