Spindle cell variant of epithelioid cell histiocytoma (spindle cell histiocytoma) with ALK gene fusions: Cases series and review of the literature.

EFH is not always purely epithelioid and its spindled cell variant, spindle cell histiocytoma, should be included in the differential diagnosis of superficial dermal spindled cell neoplasms. ALK immunostain is a useful diagnostic marker for this entity and further studies may be useful to investigate whether DCTN1-ALK fusion mutations are specific to EFH with spindled cell features.