Key result
Break-apart FISH and immunohistochemistry confirm ALK rearrangement in pediatric localized ALK-positive histiocytosis.
Why the study?
Morphological diagnosis of ALK-positive histiocytosis can be challenging due to overlapping morphology and limited case reports.
What are the clinicopathological features of localized ALK-positive histiocytosis in pediatric patients?
Case Report (n=3)
What are the clinicopathological features of localized ALK-positive histiocytosis in pediatric patients?
ALK immunohistochemistry and molecular testing facilitate definitive diagnosis of localized ALK-positive histiocytosis, which can morphologically overlap with juvenile xanthogranuloma and Rosai-Dorfman disease.
May support ALK testing to distinguish pediatric histiocytosis from JXG/RDD; hypothesis-generating from case reports, needing larger validation.
ALK-positive histiocytosis is a systemic or localized form of histiocytosis that is associated with ALK gene rearrangements. Morphological diagnosis of this entity can be challenging due to overlapping morphology and limited case reports. We describe the clinicopathological features of localized ALK-positive histiocytosis in three pediatric cases. The main features were the presence of typical histiocytes and spindle-shaped cells with varying numbers of giant cells, which can exhibit emperipolesis . Neoplastic cells lacked significant atypia, mitotic activity, or pleomorphism. Immunohistochemistry showed positivity for histiocytic markers and ALK (clone 137E9E8). Break-apart FISH confirmed ALK rearrangement. Morphological overlap with juvenile xanthogranuloma and Rosai-Dorfman disease was observed. ALK immunohistochemistry and molecular testing facilitated definitive diagnosis.
No takes yet. Share an insight, caveat, or question.
Zhang et al. (2026) conducted a case report in Localized ALK-positive histiocytosis (n=3). In three pediatric cases, localized ALK-positive histiocytosis presented with typical histiocytes and spindle-shaped cells, with definitive diagnosis facilitated by ALK immunohistochemistry and FISH.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: