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The diagnosis of lymphomas and cancers of blood cells is sometimes less certain than the diagnosis of other forms of cancer. Often, the appearance of the cells under the microscope is not sufficiently distinct to say with certainty the exact form of disease which is present. Quite frequently, additional information may be obtained with immunological techniques. With the widespread commercial availability of specific antibodies, it is possible to identify specific antigens (substances which stimulate the formation of antibodies) in the specimen to provide important clues to the pathological entity present. However, there are cases in which even these clues are not adequate for a conclusive diagnosis. As the techniques of molecular genetics become more widely used in laboratories, it will become possible to examine the actual genetic composition of a cancer specimen to obtain further clues to its identity. The examination of the genes of a specimen, called genotyping, was evaluated as a possible diagnostic tool in 175 cases of lymphoma or related lesions. Conventional methods could be used to assign the diagnosis with confidence in 90 cases (control cases). The remaining 85 cases posed diagnostic problems. In the control group, all the cases which had been diagnosed as non-Hodgkin's lymphoma showed characteristic gene rearrangements. Immunological techniques were about as good for confirming the diagnosis in this group, so the molecular genetic analysis provided no advantage in this group. However, the same was not true in the category of problem diagnoses. Not considering four cases which turned out to be Hodgkin's lymphoma, molecular genotyping contributed useful diagnostic information in 58 of 81 problem cases. In 25 of these 58 cases, the information provided by molecular genotyping was considered to be instrumental in arriving at the proper diagnosis. In 23 cases, no useful information was provided by the genotyping technique. The results show that genotyping is a sensitive and specific tool for the diagnosis of lymphomas and similar but benign lesions. However, in most cases the diagnosis may be made successfully without this tool. In cases which remain uncertain after use of conventional diagnostic techniques, molecular genotyping may prove to be useful. (Consumer Summary produced by Reliance Medical Information, Inc.)

Malignant histiocytosis is a syndrome characterized by the overgrowth of cells that resemble abnormal histiocytes, cells present in all connective tissues. Histiocytes are capable of phagocytic activity, in that they can ingest foreign particles. Tissues from 15 cases of malignant histiocytosis were characterized using antibodies, and were reclassified as various types of malignant lymphoma. Antibodies are immune proteins that bind to specific elements called antigens and can be used to identify certain cell types that contain these antigens. The antibodies used were capable of detecting immune T- and B-cells, as well as antigens from other types of cells such as leukocytes, monocytes, and macrophages. T-cell antigens were identified in nine cases, B-cell antigens in two cases, and no specific cell type was seen in three cases. Lymph node biopsy was performed in 12 of 15 cases, and various patterns of involvement were noted. One case was characterized by virus-associated hemophagocytosis, the ingestion of red blood cells by phagocytes. These results are consistent with previous findings which indicate most cases of malignant histiocytosis are lymphatic cancers associated with T-cells. It is suggested that the term malignant histiocytosis be replaced by large cell lymphoma. (Consumer Summary produced by Reliance Medical Information, Inc.)

Tumors of the thymus are rare, and may exist in three forms: benign thymoma, malignant thymoma, and thymic carcinoma. The latter two are distinguished by the fact that the malignant thymoma shows signs of invasion or spread, although the cells themselves are histologically normal, while the cells of the thymic carcinoma are histologically atypical. The preferred treatment for thymic carcinoma is surgery, as chemotherapy is generally ineffective. Therefore, the prognosis for patients with thymic carcinoma that has already spread is poor. However, a case is now reported in which a patient with metastatic thymic carcinoma was chemotherapeutically treated and remains a long-term survivor without evidence of disease after five years. The patient, a 21-year-old male, had a chest mass, and tumor cells within a lymph node were revealed by biopsy. Although a germ cell tumor had been suspected initially, histological appearance of the lymph node was consistent with metastatic thymic carcinoma. The patient was treated with a combination regimen including cisplatin, vinblastine, bleomycin, and etoposide. After four cycles of chemotherapy, the area of the chest mass was surgically removed; examination revealed only scar tissue with no live tumor cells, indicating a complete response to the chemotherapy. Two additional cycles of chemotherapy were given after surgery as consolidation therapy. Although the optimum therapy for metastatic thymic carcinoma remains unknown, the success with this patient indicates that a combination therapy including cisplatin and bleomycin and either vincristine or etoposide may be a good choice for first-line treatment. (Consumer Summary produced by Reliance Medical Information, Inc.)