Aim: Pathohistological diagnostics (PD) of the Yolc Sac tumor (YST) of primary mediastinal localization. Introduction: YST are malignant germ cell tumors of primitive endodermal gonadal differentiation. In 1% -5% of cases their localization is extragonadal, including mediastinal in 50% -70% published cases. Case report: A 30-year-old man was admitted to the Thoracic Surgery Clinic for diagnosis and treatment of mediastinal tumor with lungs and liver metastases. Laboratory analyzes revealed high elevations in serum alpha-fetoprotein (AFP), in addition moderate elevation of beta-chorionic gonadotropin (ß-HCG). No pathological changes in testis and retroperitoneum have been found. An open biopsy of the mediastinal change was made for PD. Histologically, tumor tissue showed a significant degree of necrosis. There were reticular, microcystic and pseudopapillary forms of neoplastic cell growth, surrounded by myxomatosis stroma. Tumor cells cytoplasm was scarce and vacuolated with high nuclear polymorphism and hyperchromasia. Positive immunohistochemical (IMH) reaction was obtained for panCK, AFP, PLAP. Immunoreactivity for TTF-1 was found in about 50% of tumor cells, as well as the focal reaction for ß-HCG in rare multinuclear cells. Reactions for D2-40, CD5, CK-7, CK-20, p63, CD117, CD30, napsin A and calretinin were negative. Conclusion: The results of our analysis showed the expression of divergent endodermal linear markers in the mediastinal YST, especially TTF-1 expression. The diagnosis of YST in small biopsies can be difficult and requires using of a wide range of IMH markers in order to closer the differentiation of primary tumor localization and the application of appropriate chemotherapy

Aim: Purpose of this report is to present metastasis of lymph nodes melanoma with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) as an example of collision tumor of an uncommon synchronic occurrence in the lymph node. Introduction: Synchronic, composite tumors are rare and their simultaneous and synchronic occurence within the same tissue/organ is even more rare. CLL/SLL is an indolent, clonal disease of mature B-lymphocytes which occurs mostly with adults. After the treatment with chemotherapeutic agents the occurence of the secondary malignancies (melanoma,squamous-cell carcinoma). Material and Methods: We present a 77 year old male who, after right sided nephrectomy caused by clear-cell carcinoma was diagnosed with CLL/SLL with bone marrow and lymph node infiltration. After three years and chemotherapy, skin changes were excised which histomorphologically resembles melanoma. After the immunotherapy for melanoma, the enlarged lymph nodes were extripated from the neck and histomorphologically and immunohistochemically treated. Results: Histomorphologically, a diffused infiltration of small B-lymphocytes was found in the lymph node, with round nuclei, condensed chromatin, inconspicuous nucleoli, scant cytoplasm unique immunophenotype: CD20 ,PAX-5 ,CD5 ,CD23 ,Cyclin D1-,CD3-. A part of lymph node was infiltrated by epitheloid cells with immunohistochemic profile: S-100 ,Melan A ,HMB-45 . Histomorphological and immunohistochemical CLL/SLL with melanoma infiltration as an example of a collision tumor was proved. Conclusion: Lymphoproliferative neoplasms including CLL/SLL represent an risk of synchronous, metachronous development of secondary malignancies including melanoma itself and they can uncommonly present themselves as synchronic collision tumors within the same organ.