Primary central nervous system ALK-positive anaplastic large cell lymphoma
see also Primary central nervous system ALK-negative anaplastic large cell lymphoma.
It is a T-cell lymphoma that has been recognized as a distinct entity in the WHO classification of tumors of hematopoietic and lymphoid tissues. It is most frequent in youth. It involves both lymph nodes and extranodal sites but rarely be found in the central nervous system (CNS) 1). Besides, ALK + ALCL shows a broad morphologic spectrum, such as the common, small cell, lymphohistiocytic, Hodgkin-like, and occasional alveolar growth patterns 2) 3). All cases contain a variable proportion of characteristic hallmark cells with expression of ALK protein and CD30 facilitating accurate diagnosis. However, other lymphoid tumors such as some diffuse large B-cell lymphoma and NK/T-cell lymphoma can express CD30, and the latter mainly possess CD56-positive tumor cells, it’s definitely challenging in such a situation 4).
Case reports
A 12-year-old Chinese male presented with a headache and emesis for a couple of days. The neoplastic component was smaller cells resembling starry-sky growth patterns and immunohistochemically stained positively for CD30, ALK1, and CD56. Monoclonal T-cell receptor (TCRγ) gene rearrangement and gene translocation involving ALK identified by fluorescence in situ hybridization (FISH) using ALK break-apart probe supported the diagnosis of ALK + ALCL. This case showed ALK + ALCL occur in a rare site with an abnormal CD56 expression. Awareness of this entity is important to distinguish it from other intracranial lymphomas 5).
A 34-year-old Chinese male patient who presented with headache, diplopia, and vomit. Cerebrospinal fluid (CSF) analysis via lumbar puncture showed elevated CSF pressure, elevated CSF protein concentrations, decreased CSF glucose and chloride concentration significantly, and pleocytosis of 68 to 350 × 10/L, in which lymphocytes and monocytes were predominant. These changes could be suggestive of tuberculous (TB) meningitis. Enhanced magnetic resonance imaging of spinal cord delineated multiple enhancing nodules in spinal cord, cauda equina, and cristae membrane, and multiple abnormal enhancing lesions in bilateral lumbar intervertebral foramen 6).
A 31-year-old Korean male presented with altered consciousness and severe headache. Brain MRI delineated focal leptomeningeal enhancement without any intracerebral lesions. Diagnosis was made based on a brain biopsy showing anaplastic large cell lymphoma (ALCL), immunohistochemical stains revealing positivity for anaplastic lymphoma kinase (ALK) and an absence of involvement in any other organs; specifically, the primary central nervous system ALK+ALCL. Complete remission was achieved following 5 cycles of systemic chemotherapy with a high dose of Methotrexate and a simultaneous 7 cycles of intrathecal triple chemotherapy. Diagnosis of primary leptomeningeal ALK+ALCL is challenging given its rarity and non-specific symptoms along with non-pathognomonic radiologic findings. We present the first case of primary leptomeningeal ALK-positive ALCL where the clinical course, pathologic characteristics and treatment modality are described as well as a review of literature 7).