Thymic tumor with adenoid cystic carcinomalike features: a clinicopathologic study of 4 cases.
ABSTRACT Thymic carcinomas are rare malignant neoplasms which comprise several histologic subtypes. Adenoid cystic carcinoma (ACC) is included among these subtypes even if it has never been formally reported. We evaluated the clinical, radiologic, morphologic, immunohistochemical, and genetic features of 4 cases of thymic neoplasms with ACC-like features retrieved from the authors' consult files. Most cases affected adult/elderly males (mean 68.5 y; range: 63 to 77 y; M:F ratio=3:1), and were asymptomatic. The clinical history (no evidence of ACC in other sites), radiologic findings (a mass in the thymic region), and morphologic features (residual thymic tissue at the periphery of the neoplasm) strongly supported their primary thymic nature. Grossly, most of the tumors presented as multicystic lesions. On microscopic examination there were true glandular spaces filled with periodic acid-Schiff+material, and pseudocysts containing stromal mucin, collagen IV, and laminin. Features favoring malignancy were overtly infiltrative margins (2/4), mitotic figures (2/4), cytologic atypia (1/4), vascular invasion (1/4), absence of organoid thymuslike pattern (4/4), and absence of immature (TdT+) T lymphocytes (3/3). Necrosis and nerve invasion were not observed. The tumor cells showed the following immunophenotype: p63+(3/3), CK34betaE12+(3/3), CD5+ in scattered cells (1/3), CD117- (3/3), chromogranin-(2/2), synaptophysin-(2/2), and CD56- (2/2). MIB-1 ranged from 1% to 10%. Comparative genomic hybridization revealed an isolated gain of chromosome 8 in 1/3 cases. One patient is alive and well after 20 months, 1 died of another cause 5 years later, and 2 were lost at follow-up. Exceptionally, primary thymic tumors may exhibit histologic features resembling those of ACC of salivary glands. They may be well circumscribed and cytologically bland or invasive and cytologically atypical. In either case they lack an organoid thymuslike pattern and immature T lymphocytes. We have interpreted them as a microscopic subtype of well-differentiated thymic carcinoma of low-grade malignancy, an impression supported by the admittedly limited follow-up information.
- Methods in Enzymology 02/2004; 382:45-67. · 2.00 Impact Factor
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ABSTRACT: The diagnosis of thymic epithelial neoplasms is normally rendered after careful evaluation of their histologic features. In some cases, however, the morphological heterogeneity or overlap with neoplasms of other organ systems can lead to diagnostic uncertainty. On the basis of this, the use of immunohistochemical stains as a diagnostic adjunct has become a popular tool. Although undoubtedly, immunohistochemistry has its role in the diagnosis of difficult cases, to date there are no specific markers that would distinguish thymic epithelial neoplasms from other tumors and interpretation of immunohistochemical results should only ever be made in conjunction with accurate morphologic analysis and careful clinical evaluation. This article will review the current knowledge of the immunohistochemical phenotype of thymic epithelial neoplasms with particular emphasis on its use for diagnostic purposes and the latest advances in this field.06/2014;
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ABSTRACT: Thymic carcinoma (primary carcinoma of the thymic epithelium; type C thymoma) is a rare malignancy. It usually presents in middle-aged to elderly patients and can exhibit a wide variety of morphologic appearances. Thymic basaloid carcinoma (thymic BC) is a particularly rare subtype, with less than 20 cases published in the English literature, mostly in the form of individual case reports. In this study, we present the clinicopathologic and immunohistochemical features of 12 new cases of thymic BC. There were 10 (83%) men and 2 (17%) women. Ages at the time of initial diagnosis ranged from 34 to 77 years (mean 55 y). The 2 most common manners of presentation were dyspnea on exertion (3 patients) and as an incidental finding on radiographic imaging (2 patients). Tumors ranged in size from 4.4 to 17 cm (mean 10.1 cm). One of 12 cases (8.3%) was associated with a multilocular thymic cyst. Immunohistochemistry was performed in 8 cases. Pan-cytokeratin was positive in all cases. CD117 (c-kit) was positive in 6 of 8 cases (75%), p63 was positive in 7 of 8 cases (88%), p53 was positive in 7 of 8 cases (88%), ranging from <10% to 90%, CD5 was focally positive in 3 of 8 cases (38%), collagen type IV was positive in 4 of 8 cases (50%), and proliferative index, as estimated by Ki67, ranged from <1% to approximately 15%. In 1 of 2 cases with sarcomatoid differentiation, Ki67 was greater than 80% in the sarcomatoid area. Cases were negative for thyroid transcription factor-1 (0 of 8), S-100 (0 of 7), and synaptophysin (0 of 7). Long-term data was available in 8 patients with an average follow-up of 30 months. Five patients died of their disease at an average of 34 months from the time of diagnosis. Of the remaining 3 patients, 1 had a stable recurrence and died at 4 years from unrelated causes, and 2 were alive without the evidence of disease at 12 and 7 months, respectively. Thymic BC, although previously regarded as a low-grade neoplasm, has shown that it is capable of aggressive behavior and significant mortality. In this paper, we review the pertinent literature and discuss the possible relationship of thymic BC with thymic adenoid cystic carcinoma, as well as BCs and adenoid cystic carcinomas at other sites.The American journal of surgical pathology 05/2009; 33(8):1113-24. · 4.06 Impact Factor