Primary anaplastic large T cell lymphoma of central nervous system

Background Primary anaplastic large T cell lymphoma (ALCL) of central nervous system (CNS) can occur in people of all ages, and is usually unrelated with immunodeficiency. It is often misdiagnosed as meningitis, especially tuberculous meningitis, on clinical practice and imaging examination. In pathological diagnosis, the morphological changes of primary ALCL of CNS are similar to the systemic ALCL and the anaplastic lymphoma kinase⁃1 (ALK⁃1) can be positive or negative. Being misdiagnosed as meningitis, hormone therapy with glucocorticoid before biopsy is always used, and massive necrosis and a lot of histocyte proliferation and phagocytosis can be found under histological findings. Therefore, when the material is not enough, primary ALCL of CNS is often misdiagnosed as cerebral infarction or malignant histocytosis and so on. This paper reports a case of primary ALCL of CNS and makes a review of relevant literature, so as to summarize the clinical manifestations and elevate the recognition of clinicians and pathologists on this disease. Methods and Results A 12⁃year⁃old boy was admitted because of fever, worsening headache, numbness and weakness of right limbs. MRI showed local gyri swelling and abnormal enhancement of pia mater in the right parietal lobe, expanding to the right temporal lobe, and pia mater enhancement in the left parietal lobe. The right temporo⁃parietal lobe lesion biopsy revealed irregularly shaped tumor cells of large size, rich and eosinophilic cytoplasm and horseshoe⁃shaped or kidney⁃shaped nuclei. Immunohistochemical examination showed tumor cells positive for CD3, CD45RO, CD30, ALK⁃1 and epithelial membrane antigen (EMA), and negative for CD20 and CD79a. Conclusion Primary ALCL of CNS is an extremely rare tumor which is usually misdiagnosed as meningitis according to clinical andimaging examinations. Therefore, for those patients who are considered as meningitis but with poor treatment effect and replase of illness, brain tissue biopsy, which is an important means for diagnosis, or cerebrospinal fluid cytologic examination, should be carried out as soon as possible.