2026 Volume 13 Pages 417-418
We thank the correspondents for their insightful comments regarding our article, "Thoracic Intradural Extramedullary Cavernous Malformation Mimicking Meningioma."1) We particularly appreciate their suggestion to consider capillary hemangioma (CH) in the differential diagnosis, given these 2 entities share overlapping radiological features and can be easily confused in clinical practice.
The correspondents accurately noted that the strong, homogeneous contrast enhancement and the absence of a prominent T2-weighted hypo-intense rim in our case are features frequently associated with CH. Indeed, as previously reported in this journal,2) the lack of classic cavernous malformation (CM) imaging markers such as the popcorn appearance commonly observed in intramedullary lesions often makes the preoperative distinction between CM and other intradural extramedullary tumors a significant challenge.3,4) However, the definitive differentiation between these vascular lesions rests on detailed histopathological findings. In response to the points raised by the correspondents, we performed additional specialized staining to further clarify the nature of the lesion. We report that Berlin blue staining indicated definite hemosiderin deposition within the stroma and the periphery of the vascular channels. Although CH is a neoplastic proliferation of capillary-sized vessels that typically lacks evidence of prior hemorrhage,2) CM is characterized by dilated caverns tending to chronic, low-pressure micro-bleeding. The presence of hemosiderin, confirmed by Berlin blue, serves as a critical histological marker that distinguishes CM from CH, even when the classic magnetic resonance imaging hemosiderin rim is absent.
We agree with the correspondents that the natural history and bleeding risk of CH may differ from those of CM. However, the evidence of subclinical micro-bleeding in our patient suggests that intradural extramedullary CMs retain their inherent tendency for micro-bleeding, necessitating a cautious clinical approach.3) The identification of hemosiderin not only validates our diagnosis of CM but also provides a clearer understanding of the lesion's potential for neurological progression.
We are grateful to the correspondents for prompting this deeper pathological inquiry. The identification of hemosiderin deposition through specialized staining clarifies the diagnostic ambiguity and underscores the importance of Berlin blue in the differential diagnosis of spinal vascular lesions. This dialogue contributes to a more robust classification of these rare pathologies.
Sincerely,
Shingo Toyota
Author Dr. Kishima, Haruhiko is one of the Editorial Board members of the Journal.
This author was not involved in the peer-review or decision-making process for this paper.
All authors have no conflict of interest.
