title: ALK+ histiocytosis: a novel type of systemic histiocytic proliferative disorder of early infancy.
abstract: We report 3 cases of a previously uncharacterized form of histiocytosis presenting in early infancy and showing ALK immunoreactivity. The patients presented with pallor, massive hepatosplenomegaly, anemia, and thrombocytopenia. Liver biopsy showed infiltration of the sinusoids by large histiocytes with markedly folded nuclei, fine chromatin, small nucleoli, and voluminous lightly eosinophilic cytoplasm that sometimes was vacuolated or contained phagocytosed blood cells. One patient developed cutaneous infiltrates that morphologically resembled juvenile xanthogranuloma. The histiocytes were immunoreactive for histiocytic markers (CD68, CD163, lysozyme), S100 protein, ALK (membranous and cytoplasmic pattern), and dendritic cell markers (fascin, factor XIIIa), but not CD1a and langerin. One case successfully analyzed by molecular techniques revealed TPM3-ALK fusion. Thus the spectrum of diseases exhibiting ALK translocation should be expanded to include ALK(+) histiocytosis. The disease in the 3 patients (2 having been given chemotherapy) resolved slowly over many months.
authors.affiliation: Department of Pathology, Queen Elizabeth Hospital, Kowloon, Hong Kong. jkcchan@ha.org.hk
authors.forename: John K C
authors.initials: JK
authors.lastname: Chan
authors.forename: Laurence
authors.initials: L
authors.lastname: Lamant
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Algar
authors.forename: Georges
authors.initials: G
authors.lastname: Delsol
authors.forename: William Y W
authors.initials: WY
authors.lastname: Tsang
authors.forename: King C
authors.initials: KC
authors.lastname: Lee
authors.forename: Karin
authors.initials: K
authors.lastname: Tiedemann
authors.forename: Chung W
authors.initials: CW
authors.lastname: Chow
mesh_terms: D030301:Activin Receptors, Type II / Q000378:metabolism*; D001706:Biopsy; D049109:Cell Proliferation; D005260:Female; D006644:Histiocytes / Q000473:pathology*; D015614:Histiocytosis / Q000473:pathology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008099:Liver / Q000473:pathology; D021381:Protein Transport; D012867:Skin / Q000473:pathology
chemical_list: C425364:ACVRL1 protein, human; D030301:Activin Receptors, Type II