Article

Immunohistochemical KIT (CD117) expression in thymic epithelial tumors

Japan Research Institute, Edo, Tōkyō, Japan
Chest (Impact Factor: 7.13). 08/2005; 128(1):140-4. DOI: 10.1378/chest.128.1.140
Source: PubMed

ABSTRACT 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.

0 Followers
 · 
127 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The prognostic importance of histologic classifications of thymic epithelial neoplasms is controversial. Evidence suggests that difficulties in reproducibility affect prognostic studies. Two thoracic pathologists independently classified 80 cases of type A or B3 thymoma and thymic carcinoma according to World Health Organization (WHO) classification. Ki-67 labeling index (LI) was used to identify cutoff points between WHO types. Recursive partitioning (Rpart) and ad hoc methods separated the data points. The pathologists agreed on type A (n = 31), type B3 (n = 21), and thymic carcinoma (n = 14). Ki-67 LI differed between types A and B3 (P < .001) and between thymic carcinoma and type A (P < .001) or type B3 (P = .001). Mitotic activity differed between thymic carcinoma and type A (P < .001) or type B3 (P < .001). Rpart revealed Ki-67 LI greater than 14.0% only in thymic carcinoma; cases with Ki-67 LI less than 5.1% did not represent thymic carcinoma. Ad hoc analysis showed Ki-67 LI greater than or equal to 13.5% represents thymic carcinoma; only type A had Ki-67 LI less than 2%. The pathologists disagreed on histologic type in 14 cases. In 11 of 14 cases with available Ki-67, the Rpart method predicted the WHO type; in 7 of 14 cases, the ad hoc method predicted the WHO type. In conclusion, Ki-67 LI is helpful in differentiating thymic epithelial neoplasms, with Ki-67 LI less than 2% and greater than or equal to 13.5% distinguishing type A thymoma and thymic carcinoma, respectively. Copyright © 2014 Elsevier Inc. All rights reserved.
    Human pathology 10/2014; 46(1). DOI:10.1016/j.humpath.2014.10.001 · 2.81 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The rapid advent of technology in recent years has resulted in a substantial increase in our knowledge of the molecular underpinnings of thymic epithelial tumors. In addition to previously described chromosomal aberrations and alterations in DNA methylation, genome sequencing has helped unravel hitherto unknown mutations in these tumors. Attempts are also being made to develop gene signatures to help in the identification of patients likely to benefit from adjuvant therapy. Some of the recently identified genetic alterations have the potential to serve as targets for biological therapy, thus opening newer avenues for treatment of thymic epithelial tumors and increasing the number of effective options for treatment of recurrent or refractory disease.
    Journal of thoracic oncology: official publication of the International Association for the Study of Lung Cancer 09/2014; 9(9 Suppl 2):S131-S136. DOI:10.1097/JTO.0000000000000298 · 5.80 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A 69-year-old man was referred to our hospital in June 2010 after the diagnosis of an anterior mediastinal tumor and HIV infection. Histopathological examination of a CT-guided needle biopsy specimen showed undifferentiated thymic carcinoma. Chest CT revealed pleural dissemination, bone invasion, and left lung metastases. The final diagnosis was Masaoka stage IVb. Surgery was considered inappropriate. Instead, the patient first underwent highly active antiretroviral therapy for HIV infection, followed by four courses of cisplatin, doxorubicin, vincristine, and cyclophosphamide chemotherapy for thymic carcinoma. A partial response was achieved. To our knowledge, this is the first report of thymic carcinoma in an adult patient with HIV infection.
    07/2012; 1(3):142-146. DOI:10.1007/s13691-012-0027-0