Classification of non-Hodgkin lymphoma in Central and South America: a review of 1028 cases.

The distribution of non-Hodgkin lymphoma (NHL) subtypes differs around the world but a systematic study of Latin America has not been done. Therefore, we evaluated the relative frequencies of NHL subtypes in Central and South America (CSA). Five expert hematopathologists classified consecutive cases of NHL from 5 CSA countries using the WHO classification and compared them to 400 cases from North America (NA). Among the 1028 CSA cases, the proportions of B- and T-cell NHL and the sex distribution were similar to NA. However, the median age of B-cell NHL in CSA (59 years) was significantly lower than in NA (66 years; P < .0001). The distribution of high-grade (52.9%) and low-grade (47.1%) mature B-cell NHL in CSA was also significantly different from NA (37.5% and 62.5%; P < .0001). Diffuse large B-cell lymphoma was more common in CSA (40%) than in NA (29.2%; P < .0001), whereas the frequency of follicular lymphoma was similar in Argentina (34.1%) and NA (33.8%), and higher than the rest of CSA (17%; P < .001). Extranodal NK/T-cell NHL was also more common in CSA (P < .0001). Our study provides new objective evidence that the distribution of NHL subtypes varies significantly by geographic region and should prompt epidemiologic studies to explain these differences.

Non-Hodgkin lymphoma in Chile: a review of 207 consecutive adult cases by a panel of five expert hematopathologists.

The distribution of subtypes of non-Hodgkin lymphoma (NHL) in Latin America is not well known. This Chilean study included 207 consecutive cases of NHL diagnosed at five cancer centers in the capital, Santiago, and one center in Viña del Mar. All cases were reviewed and classified independently by five expert hematopathologists according to the 2001 World Health Organization classification of NHL. A consensus diagnosis of NHL was reached in 195 of the 207 cases (94%). B-cell lymphomas constituted 88% of NHL, and diffuse large B-cell lymphoma (DLBCL, 38.5%) and follicular lymphoma (25.1%) were the most common subtypes. There was a high frequency of marginal zone B-cell lymphoma (10.3%), as well as of extranodal natural killer (NK)/T-cell lymphoma, nasal type (2.6%) and adult T-cell leukemia/lymphoma (0.5%). Extranodal presentation was seen in 74 of the 195 cases (38%) and the most common extranodal presentation was in the stomach (37.6%). The most common gastric lymphoma was DLBCL (54.5%) followed by mucosa-associated lymphoid tissue (MALT) lymphoma (41%). Overall, the frequency of NHL subtypes in Chile is between that reported in Western and Eastern countries, which is probably a reflection of the admixture of ethnicities as well as the environment and socioeconomic status of its population.

Classification of non-Hodgkin lymphomas in Guatemala according to the World Health Organization system.

The aim of this study is to report the relative frequencies of non-Hodgkin lymphoma (NHL) subtypes in Guatemala. A panel of five hematopathologists reviewed 226 consecutive biopsies and classified them according to the 2001 World Health Organization (WHO) classification. The 83 cases of diffuse large B-cell lymphoma (DLBCL) were further subclassified into germinal center B-cell-like (GCB) and non-GCB subtypes. Of the 226 cases, 194 (86%) were confirmed as NHL, including 169 (87%) B-cell and 25 (13%) T- or natural killer (NK)-cell NHL. The most common subtype was DLBCL (44.3%), and the most frequent subtype among T- and NK-cell NHL was extranodal NK/T-cell lymphoma, nasal type (7.8% of all NHL). A comparison of the frequencies of NHL subtypes between Guatemala and other parts of the world showed that Guatemala is most similar to the Middle East and Asia. However, there is no significant difference in the frequency of the DLBCL subtypes compared to North America and Europe.

HTLV-positive and -negative T-cell lymphomas. Morphological and immunohistochemical differences between European and HTLV-positive Japanese T-cell lymphomas.

A total of 56 cases of malignant lymphoma presumed to be of peripheral T-cell origin were investigated with regard to histological and immunohistochemical features. The goal of the study was to determine whether virus-associated T-cell lymphomas can be morphologically or immunohistochemically distinguished from presumably virus-negative T-cell lymphomas. The cases came from endemic and non-endemic regions of Japan, the United Kingdom (including 4 Caribbean cases) and the Federal Republic of Germany. Sera of all Japanese and Caribbean patients and 8 German patients were tested for antibodies to adult T-cell leukaemia virus-associated antigen HTLV-A. In all cases sections were examined blind by 5 well-trained histopathologists. In most cases cryostat sections could be prepared from fresh tissue specimens and stained with a large panel of monoclonal antibodies. All HTLV-A-positive cases were morphologically classifiable as the pleomorphic type of T-cell lymphoma. Approximately 70% of the tested cases of pleomorphic T-cell lymphoma, however, showed a positive serum reaction for HTLV-A. All other types of peripheral T-cell lymphoma (T-immunoblastic lymphoma, chronic lymphocytic leukaemia of T type, T-zone lymphoma, "AILD type" and lymphoepithelioid cell lymphoma) were HTLV-A-negative and mostly observed in European patients. Thus virus-associated T-cell lymphomas appear to be invariably of the pleomorphic type; but pleomorphism is not specific to HTLV-A-positive cases. This was also evident from the results of an experiment in which 2 Japanese histopathologists attempted to recognize HTLV-A positivity in a blind study of pleomorphic T-cell lymphomas. A maximum of about 80% of cases were correctly identified, with about 10% false-positive diagnoses (in HTLV-A-negative or presumably negative cases) and 10% false-negative diagnoses. The immunohistochemical analysis revealed not only many common features but also 2 distinct differences between HTLV-A-positive and -negative T-cell lymphomas. All but one of the HTLV-A-positive cases showed reactivity with anti-Tac and all cases in the virus-positive group were negative for TU14. All other cases were Tac-negative and approximately 65% of these cases exhibited reactivity with TU14. Preliminary cytogenetic observations suggest that there are also differences in specific chromosome aberrations.