The role of histopathologic examination of intracranial blood clots removed for hemorrhage of unknown etiology: a clinical pathologic analysis of 31 cases.

Intracranial hemorrhage is a well recognized cause of morbidity and mortality. Often, the etiology of the hemorrhage is known before surgical intervention, ie, evacuation of the hematoma. In a subset of patients, however, no known cause for the hemorrhage has been found in either history (eg, trauma) or radiographic findings (eg, tumor) before surgery. We retrospectively reviewed 54 blood clot evacuation specimens received in the surgical pathology department over a 16-year period (1983-1999). Cases were excluded in which the hemorrhage was attributed to or associated with prior trauma or for which there was a prior known cause of the hemorrhage. Thirty-one cases fulfilled the study requirements and comprised the study group. Thirty-one patients (aged 7 to 79 years; mean 54 years), including 16 females and 15 males, formed the study group. In 14 cases (45%), only blood clot was identified in the tissues examined. Of the remaining 17 cases, specific pathologic diagnoses were made in nine instances including cerebral amyloid angiopathy in three cases, arteriovenous malformations in three cases, and tumors in three cases. Tumor types included metastatic non-small cell carcinoma in two cases and low-grade astrocytoma in one case. Examination of blood clot evacuation specimens can lead to a discovery of the etiology of the hemorrhage in a subset of cases, particularly if neural tissue is part of the specimen. The quantity of neural tissue submitted for histologic evaluation seems to correlate with a higher likelihood of making a diagnosis. The routine use of Congo red stain in all adult cases in which brain tissue is present proved to be of diagnostic utility in screening for amyloidosis.