Intravascular (blood vessel) histiocytosis with haemophagocytosis

Aims Many types of intravascular lymphohistiocytic proliferation have been described recently; this was previously an unnoticed or misinterpreted phenomenon. Intralymphatic lymphohistiocytic aggregates are relatively common, and include benign, malignant and indeterminate conditions. In contrast, all non‐endothelial proliferations in the lumina of blood vessels have been interpreted so far as malignant. Herein, we present three cases of histiocytic proliferations in the lumen of blood vessels associated with intracytoplasmic granulocyte debris (haemophagocytosis), a previously undescribed entity. Methods and results We identified three patients from two institutions with similar cutaneous lesions, both clinically and microscopically. Information regarding clinical history, histological features and immunoprofiles were obtained. The three cases presented intravascular histiocytosis with haemophagocytosis involving blood vessels of the dermis, a process that may be representative of a new entity. The patients were two women and one man who presented a symmetrical reticulated erythema with a tendency to involve the skin of the breasts. The lesions were indolent, did not ulcerate and followed a benign course. Conclusion This seemingly novel condition is characterized by the presence of histiocytic cells inside blood vessels, where they have not been described previously as an entity. The most reasonable explanation for this process is an origin from the non‐classical subset of monocytes that ‘patrol’ the inner face of blood vessels acting as macrophages. The existence of this entity should be kept in mind to avoid overdiagnosis of malignancy.