TdT activity in B cell ALL.

trichrome (deep red) and Mallory phosphotungstic acid hematoxylin (deep blue). In addition, fibrin thrombi were observed in some sinuses. Rickettsiae were not found. In these two patients similar changes were also noted in liver biopsies: granulomas with fibrinoid ring and fibrin thrombi. Bone marrow changes in Q fever are not surprising because of the systemic distribution of the disease. These lesions, quite similar to those described by Ende and Gelpi,’ may be explained by the vascular tropism of Rickettsiae. The angiitis could be responsible for the fibrin thrombi and fibrinoid ring. Nevertheless, after biopsies were cut serially we interpreted the Icsion portrayed in the inset of Fig. I differently than they did. In our opinion the clear central space was not a vestigial vascular lumen but an adipocyte incorporated in the developing granuloma. As the result of granuloma in Q fever, this disease has to be considered among the possible diagnosis of bone marrow granulomas. Nevertheless, the presence of the singular fibrinoid ring, within or around the granuloma, is a diagnostic aid for the pathologist.