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2021, Volume 37, Number 2, Page(s) 172-177
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DOI: 10.5146/tjpath.2020.01507 |
ALK-Positive Histiocytosis: A Case Report and Literature Review |
Omar Issa JABER1, Doa’ AL JARRAH1, Mohammad HIASAT2, Maysa AL HUSSAINI1 |
1Department of Pathology and Laboratory Medicine, King Hussein Cancer Center, AMMAN, JORDAN 2Neuron Clinics, AMMAN, JORDAN |
Keywords:
Histiocytosis, Anaplastic lymphoma kinase (ALK), Adult, Spinal cord |
ALK positive histiocytosis is a relatively new histiocytic proliferation disease with a characteristic gene translocation involving fusion of the
ALK gene with different partners, mostly KIF5B. We report a case of ALK-positive histiocytosis with literature review. A 27-year-old male
patient presented mainly with progressive lower limb weakness. Imaging studies showed an intradural extramedullary enhancing lesion at
the L3 level. A 1.5 cm mass was excised from the sensory nerve root in the filum terminale at the level of L3. Histologic examination showed
infiltration of the nerve by numerous histiocytes with moderate to abundant eosinophilic to clear-foamy and variably-vacuolated cytoplasm with
irregular-to-smooth contoured nuclei. The histiocytes were positive for CD68 and ALK1 and negative for S100 and CD1a. KIF5B-ALK fusion
was detected by real time-polymerase chain reaction. The patient is asymptomatic nine months after surgical excision. This is the first reported
localized case occurring in the nerve root of an adult patient, thus expanding the clinical manifestations of this disease. An integrated histological,
immunohistochemical and molecular approach is recommended for diagnosis. We recommend performing ALK1 immunohistochemical stain
on all histiocytosis cases to increase awareness and detection of this newly described entity.
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