Introduction Lymphoma represents one of the major health problems all over the world. NHLs are slightly more common in developed countries (50.5% of cases worldwide), with rates highest in Australia and North America, intermediate in Europe (except Eastern Europe) and the Pacific islands, and relatively low throughout Asia and Eastern Europe. 1 The incidence of NHL has doubled over the past two decades in the United states (US) and most other western countries. 2 It is one of the most common cancers in the United States, accounting for 4% of all cancers. 3 At national level, NHL is 4th most common malignancy in males accounting for 6.1%. 4 According to the first population-based study of NHL in Pakistan, a gradual increase in the annual incidence was observed (Karachi Cancer Registry (KCR) for Karachi South). 5 Improved lymphoma reporting and changes in lymphoma classification have also contributed to the increased incidence of disease, and it is continuing to increase rapidly. 6 NHL is a broad category consisting of several distinct lymphoid neoplasms, presently classified according to universally accepted WHO classification, where many B and T cell subtypes are recognized. 7 Accurate classification of these requires correlation of clinical features, morphology, immunohistochemistry and genetic testing. 8 Lymphomas sometimes cause systemic symptoms, referred to as B symptoms. These include drenching night sweats, unexplained weight loss, fever and severe itching. Patients having B symptoms show a more severe condition than asymptomatic patients with the same cancer stage, tumour location or size. Onset of B symptoms at the time of diagnosis suggests that lymphoma is progressing. 9 The lymphomas encompass an array of heterogeneous malignancies. Deficient local data is available, hence clinical insight is needed to identify the exact picture of NHL for further prevention, control and disease etiology, especially in terms of efficacy of treatment protocols being followed. Hence, we conducted this study to observe the clinicopathologic variations regarding age, gender, anatomic location and occurrence of B symptoms with different subtypes of NHL. Patients and Methods All the consecutive biopsy proven cases of NHL (n=62), from October 2008 to June 2010, referred from different centres of the city, were selected for this cross 260 J Pak Med Assoc Original Article Frequency and clinicopathologic correlation of different types of Non Hodgkin’s lymphoma according to WHO classification Erum Naz, 1 Talat Mirza, 2 Sina Aziz, 3 Farheen Danish, 4 Shiza Tariq Siddiqui, 5 Adnan Ali 6 Department of Pathology, DIMC, 1,2,4,5 SZLC, Civil Hospital, 3 Department of Molecular Pathology,DDRRL, 6 Karachi. Abstract Objectives: To analyze the frequency and clinicopathologic correlation of different types of Non Hodgkin's Lymphomas (NHL) according to WHO classification of lymphoid neoplasms. Methods: Total sixty two consecutive biopsy proven cases of NHL, from October 2008 to June 2010, were selected. The inclusion criteria was, all newly diagnosed patients of NHL with appropriate clinical information regarding age, gender, anatomic location and occurrence of B symptoms. All the cases were evaluated on Haematoxylin and Eosin (H & E) and special stains. Cases were subjected to Immunohistochemistry (IHC) using extensive panel of antibodies and classified according to WHO classification of lymphoid neoplasms. Results: Clinical data showed that 42(67%) were males and 20(33%) females. The male to female ratio was 2.6:1. The age range was 6 to 80 years. Mean age for males was 39.6 ± 17.3 years and for females 45.1 ± 17.8 years. The B cell lymphoma comprised of 85.5 % as compared to T cell lymphoma consisting of 14.5%. The extra nodal involvement was seen in 25 (40.3 %) cases, while 37 (59.3%) cases showed nodal involvement. The B symptoms were found in overall 29 (46.7 %) cases. Conclusion: B cell NHL is more common as compared to T cell lymphoma. Diffuse large B cell lymphoma (DLBCL) was the most frequent B cell lymphoma. The major bulk of T cell lymphomas comprised of anaplastic large cell lymphoma (ALCL). Significant association was seen in the occurrence of B symptoms with extra nodal origin and male gender. Keywords: Non Hodgkins lymphoma, Immunohistochemistry, B cell lymphoma, B symptoms (JPMA 61:260; 2011).