Recently, I was invited by “Lymphoma” to give an interview on “The importance of pathological diagnosis of lymphoma”. The following are the answers to the questions that are of interest to patients. Is it necessary to have pathological diagnosis of lymphoma before treatment? What is the difficulty in the pathological diagnosis of lymphoma? A: Yes. The main means of confirming the diagnosis of malignant lymphoma, like other cancers, is pathological diagnosis, and histopathological diagnosis must be performed. Malignant lymphoma differs from other solid tumors in that it is actually a general term for a group of diseases with extremely complex types, including more than sixty different types or subtypes of tumors, the latter of which can be broadly categorized into two major groups, Hodgkin’s lymphoma and non-Hodgkin’s lymphoma. Non-Hodgkin’s lymphoma includes two major categories, B-cell lymphoma and T/NK-cell lymphoma, each of which can be divided into several subtypes. The biological behavior and malignancy of different types of lymphoma vary, and treatment options are also different. On the other hand, the morphology of malignant lymphomas is sometimes very similar to benign or reactive lymphoid tissue hyperplasia, which can easily lead to misdiagnosis and mistreatment, which can lead to adverse consequences. Therefore, a pathologist can only make an accurate diagnosis of such diseases after receiving specialized training and having sufficient professional knowledge and practical experience. Only when the pathological diagnosis is correct can the clinician be guided to develop the most appropriate treatment plan for the patient. What role do CT and PET-CT play in the diagnosis of lymphoma? A: CT and PET-CT examinations can help determine the number and distribution of enlarged lymph nodes or extra-nodal lesions, the size of the lesions, and the metabolic activity of the lesions, thus helping physicians to initially determine the benign and malignant nature of the lesions. However, multiple enlarged lymph nodes and large lymph node size may not always mean malignant lymphoma. On the contrary, some lymphomas, especially early lesions, do not have obvious lymph node enlargement; therefore, imaging alone cannot accurately identify benign and malignant lymphoproliferative lesions. In addition, the SUV value of PET-CT has a certain reference value for the differentiation of benign and malignant lymphoproliferative diseases and the evaluation of the efficacy. In general, lesions with high SUV values are likely to be malignant to a large extent, or, in other words, relatively malignant. However, inert lymphomas often have low SUV values and are easily missed if detected based on PET-CT alone. In addition, certain inflammatory, benign lesions have elevated SUV values. Therefore, CT and PET-CT can assess the size and number of lesions and the metabolic activity of lesions, but they are not sufficient to accurately differentiate lymphoma from reactive lymphoid hyperplasia, let alone determine the subtype of the tumor, and cannot replace histopathological diagnosis as the “gold standard” of diagnosis. How to obtain specimens for lymphoma pathology diagnosis? A: Domestic and foreign lymphoma treatment guidelines clearly point out that the first diagnosis of lymphoma must be based on histopathological examination, and the preferred and best diagnostic method is to obtain sufficient quantity and quality of tumor tissues through open surgery or endoscopic biopsy, and then make sections, stain and observe under microscope. For lesions that are inconvenient for open surgery or endoscopic biopsy (e.g. lesions deep in the body), imaging technology-mediated hollow-core needle aspiration biopsy can be used to obtain the specimen. Fine needle aspiration biopsies are generally not used as a basis for primary diagnosis, but are still of some value for initial screening of disease and determination of recurrent lesions, and in rare cases, fine needle aspiration is even the only means of pathological diagnosis. How can foreign patients go to the Department of Pathology of Cancer Hospital of Fudan University for consultation of lymphoma pathology section? A: In recent years, the number of lymphoma cases diagnosed in our hospital reaches more than 4000 cases per year, and a considerable part of them are consultation cases from all over the country. As far as the consultation process is concerned, patients or family members must bring all necessary materials for examination, including all pathological slides made by the original diagnostic unit (including HE staining, special staining, immunohistochemistry and in situ hybridization slides), the pathological diagnosis report issued by the original diagnostic unit, detailed medical history or brief description of the disease, various examination records, imaging films, etc. For some cases requiring repeat or supplemental ancillary examinations, we also need to ask patients or family members to borrow paraffin-embedded tumor tissue specimens (i.e.: wax blocks) or unstained sections cut from wax blocks (i.e.: white slices) from the original diagnostic unit in order to perform the necessary supplemental examinations. For cases requiring additional tests, the consultation opinion is usually not available on the same day. After the pathological diagnosis is completed (which usually takes one to two weeks or even longer), someone from our hospital will call the patient or family to inform them to come to the hospital to pick up the consultation report. The pick-up location is the window where they submit their documents. Patients will pick up their numbers at the kiosk, wait for the number to be called, and submit their documents to the window. After receiving the documents, the pathologist will sort them for further screening and submit them to the pathologist on duty that day, pending diagnosis.