Utility of CK7 and CK20 immunohistochemistry in the detection of synchronous breast and colon carcinoma in a pleural effusion: a case report and supporting survey of archival material.

We present a case of synchronous breast and colon carcinoma in a pleural effusion, to our knowledge the first such reported case in the English-language literature. The patient was a 55-yr-old white female with known metastatic breast and colon carcinoma who developed a malignant pleural effusion which demonstrated two strikingly different populations of malignant cells by immunohistochemical study of cell block material. One cell population demonstrated a cytokeratin (CK)7+/CK20-/ER+ phenotype, while the other demonstrated a CK7-/CK20+/ER- phenotype, consistent with breast and colon origin, respectively. An immunohistochemical survey of archival breast and colon primary and metastatic carcinomas confirmed the established CK7+/CK20- phenotype of breast and CK7-/CK20+ phenotype of colon primary carcinomas, and the maintenance of this phenotype in metastases thereof. A survey of benign and malignant mesothelial lesions confirmed the absence of staining for estrogen receptor, but showed 6/10 cases weakly positive for CK20, which has not been described in other published series. This unusual case graphically illustrates the utility of cytokeratin subset immunohistochemistry in effusion cytology.

Cytokeratin 20 immunoreactivity in renal oncocytomas.

Cytokeratins (CKs) are a group of 20 antigenically distinct intermediate filaments, generally confined to epithelia and their neoplasms. Immunostaining for CKs, in particular coordinate staining for CK7 and CK20, has become a useful tool in diagnostic pathology. Although studies defining CK distribution in neoplasms identify 0--7.7% of renal cell carcinomas (RCCs) positive for CK20, none has described the incidence of CK20 immunopositivity in renal oncocytomas (ROs). Distinction between RCC and RO may be difficult but this distinction is clinically significant, prompting us to establish the incidence of CK20 positivity in RO. We selected fifteen surgical cases of RO from our archives and studied their immunoreactivity for CKs including CK7 and CK20; 12/15 (80%) were positive for CK20, with variation in the number of cells staining. There was also variation in the distribution of CKs within the cells, including diffuse cytoplasmic, perinuclear, and a punctate or dot-like pattern. Such punctate staining corresponds to cytoplasmic balls of intermediate filaments and has been described with CAM 5.2 in RO and CK20 in Merkel cell carcinomas. Our findings suggest that CK20 immunohistochemistry is a useful tool for distinguishing RCCs from ROs. (J Histochem Cytochem 49:919-920, 2001)

Plasmacytoma with aberrant expression of myeloid markers, T-cell markers, and cytokeratin.

Plasmacytomas are localized neoplastic proliferations of monoclonal plasma cells. When multifocal, the process is referred to as multiple myeloma. These lesions exhibit a pattern of antigen expression and cytomorphology that usually leads to a ready diagnosis. However, potentially troublesome variations in immunophenotype occur. We describe a case of a plasmacytoma from a patient who presented with sudden onset of pain and a lytic lesion of the left proximal humerus. Hematoxylin and eosin-stained sections showed a lymphoproliferative lesion composed of large lymphoid cells, some with plasmacytoid and immunoblastic features. The lesion also showed significant mitotic activity. Immunohistochemical staining was positive for CD45 (LCA), CD56 (N-CAM), CD43 (MT1), and cytokeratin CAM5.2. There was also clonal staining for lambda light chains. In addition, flow cytometric analysis showed positivity for myeloid markers such as CD13, CD33, CD38, and CD138. Significant negative markers include CD20 (L26), CD45RO (UCHL-1), and CD79alpha. The unusual phenotypic features of this plasmacytoma illustrate potential diagnostic pitfalls. It is important to fully study such lesions to correctly classify them, because this has significant impact on prognosis and management.

Epstein-Barr virus-associated adult respiratory distress syndrome in a patient with AIDS: a case report and review.

BACKGROUND: Epstein-Barr virus (EBV) infection has been associated with fatal pneumonitis in immunocompetent patients. We present a case of fatal adult respiratory distress syndrome caused by EBV infection in a patient with acquired immunodeficiency syndrome (AIDS), to our knowledge the first such reported case, along with a survey of archival autopsy cases to assess baseline expression of EBV in AIDS patients. DESIGN: The case patient's autopsy material was studied exhaustively for infectious agents by culture, histochemistry, and immunohistochemistry, with negative results. Formalin-fixed paraffin-embedded lung, spleen, lymph node, and liver tissue were further studied by in situ hybridization using a probe for EBV early RNA (EBER, Kreatech). The same method was applied to lymphoid tissues from eight other archival AIDS autopsy cases. Case patient tissues were also examined by electron microscopy. RESULTS: Strikingly numerous lymphocytes were positive for EBV early RNA in the case patient's spleen, lymph nodes, and hepatic portal areas. In addition to positive lymphocytes in the lung, EBV-infected pneumocytes were also present. Electron microscopy also demonstrated viral material in lymphocytes and pneumocytes. Of the archival cases studied, only one spleen was found to have rare positive lymphocytes. CONCLUSION: Primary or reactivation EBV infection may represent a previously underreported cause of morbidity and mortality in AIDS patients. Autopsy tissues from AIDS patients do not routinely show overexpression of EBV early RNA by in situ hybridization, making this technique ideal for assessing the contribution of EBV to terminal events in these patients.