Clinical case of daily practiceA 19-year-old was assessed for pain in the right inguinal region with difficulty in complete flexion of the right leg for 3 weeks of evolution without improvement with rest and analgesia. Associated loss of 20 kg of weight in recent months with night sweating and nonspecific abdominal discomfort. Analysis detects: leukocytosis 91.0000x10E3/mcl, eosinophilia 53,6 10E3/mcl. Large abdominal mass is palpable on the right flank. Abdominal CT: Large right retroperitoneal mass with pelvic extension and right inguinal region suggestive of lymphoma. Biopsy: ALK positive anaplastic large cell lymphoma. Anaplastic large cell lymphoma (ALCL) is a peripheral T-cell lymphoma  that consists of characteristic large pleomorphic lymphoid cells with abundant cytoplasm and horseshoe-shaped nuclei, strongly positive CD30 immunohistochemical staining. It is notably more common in the first three decades and shows an overall male predominance. ALCL (ALK-positive) patients can present with variable symptoms. Most cases present with advanced stage (III-IV). Symptoms include peripheral or abdominal lymphadenopathy, extranodal infiltrates, bone marrow involvement, and B symptoms (such as fever and weight loss). In cases of BM infiltration, the patients can present with anemia or pancytopenia, eosinophilia, and high LDH.The reason for consultation of a patient does not always provide guidance during an initial assessment, but the experience of the family physician and knowing the patiente can help in diagnosis orientation.While the patients stated reason for consultation is an important starting point, it is the physicians experience and depth of knowledge about the patient that often guide the diagnostic process in primary careAnaplastic large cell lymphoma ia a rare, clinical and genetically heterogeneous subtype of mature T-Cell non Hodgkin lymphoma , but the incidence rate of  Lymphomas  among adolescents and young adults. Hodgkin lymphoma represents the most common lymphoma .Lymphoma should be considered in the differential diagnosis when a young patient  presents with constitutional symptoms  ( fever, night sweats, unintentional weight loss ) and lynmphadenopathy. These B symptoms are classic for lymphoid malignances, particulary Hodgkin lymphoma and agressive non-Hodgkin lymphomas, wich are among the most common cancer in adolescents and young adults.