Fibro-osseous pseudotumor of the digit is an unusual cutaneous process characterized histologically by a fibroblastic proliferation admixed with reactive/metaplastic osteoid formation. The osteoid formation can be florid and immature, mimicking the appearance of malignant osteoid-forming neoplasms. Fibro-osseous pseudotumor of the digit has histologic and clinical features in common with myositis ossificans. This has led many to consider the two to be synonymous. We studied three cases of fibro-osseous pseudotumor, compared to five cases of myositis ossificans, using routine light microscopy and a battery of immunohistochemical stains. Both entities displayed a "zoning" pattern of immature spindled areas admixed with more mature areas having osteoid metaplasia. This was more pronounced in myositis ossificans. In each lesion, the spindle cells stained positively for vimentin and actin. CD34 and Factor VIII highlighted the vasculature. No stromal staining for MAK-6 (cytokeratin) or S-100 was identified. Ki-67, a proliferation marker, showed positive staining of the stromal cells in both lesions, which was strongest in the immature spindled areas. The immunohistochemical and histologic similarities of the lesions support fibro-osseous pseudotumor of the digit being a cutaneous variant of myositis ossificans.

Microwave oven heating has been employed for retrieval of antigens from formalin-fued, p a d h e m b e d d e d tissue for immunohistochemical staining. Recently, a Ki-67 equivalent murine monoclonal antibody was generated which can detect tumor proliferative activity in routinely processed tissue with microwave oven heating. We assessed the effect of fixation time (4, 24, or 48 hr) and microwave oven heating time (7, 14, 21,28, 35, or 49 min) on retrieval of the Ki-67antigen from tonsil tissue. Ki-67 staining was quantitated by image analysis. Owing to the heterogeneity of Ki-67 staining within and between germinal centers, we employed a measurement technique that averages staining across the ger- IntroductionTumor proliferative activity has prognostic value in many solid tumors (1-4). Immunohistochemical analysis of tumor proliferation has been accomplished with the Ki-67 monoclonal antibody (MAb) which recognizes a nuclear antigen expressed throughout the cell cycle ( 5 ) . Unfortunately, this MAb cannot be used for retrospective studies that employ formalin-fixed, paraffin-embedded tissue. Recently, however, a Ki-67 equivalent murine MAb was generated which can detect tumor proliferative activity in routinely processed tissue (6,7). Immunohistological detection with this antibody requires antigen retrieval by microwave oven heating according to the method described by Shi et al. (8).The mechanism of action of microwave oven heating for retrieval of antigens is poorly understood. Shi et al. (8) hypothesized that the cross-linking effect of formaldehyde fixation is altered by microwave heating. They reported that tissues fixed in formalin for as long as 2 years could be stained for pancytokeratin and vimentin using antigen retrieval. However, the effect of overfixation could not be quantitatively determined because optimally fixed tissue SM is a Visiting Scientist from the Department of Obstetrics and Gynecology, Hirosaki University School of Medicine, Hirosaki, Aomori, Japan. from the same anatomic site was not available. In addition, the relationship between formalin fixation time and microwave oven heating time was not examined. We describe here the effect of fixation time and microwave oven heating time on retrieval of the Ki-67 antigen. We employed a quantitative approach with image cytometry (9,lO). Materials and MethodsTissue and Fixation. Fresh human tonsil tissue was obtained from routine surgical specimens. Tissue was cut into three equal pieces of approximately 4 mm3 and immediately fixed in 10% neutral buffered formalin for 4, 24, or 48 hr. After fixation the tissue was immersed in 70% ethanol until processing. All tissue were processed simultaneously. Fixed tissues were dehydrated in ethanol, cleared in xylene, and embedded in paraffin blocks, which were cooled before sectioning. Four-pm thick sections were cut and mounted on 3-aminopropyltriethoxysilane (APES) (Sigma; St Louis, M 0 ) -coated slides. The use of a tissue adhesive helped to prevent section detachment during microwave processing. Sec...

Inflammatory cell deposition in atherosclerotic blood vessels has been thought to relate to loss of endothelium-derived nitric oxide (NO). To examine whether cell deposition correlates temporally with the loss of NO activity, rat aortic rings were incubated with buffer, native LDL (n-LDL), oxidized LDL (ox-LDL), or the endothelium-derived relaxing factor synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) for 2 hours, and vascular contractile response to norepinephrine and relaxant response to acetylcholine, thrombin, and calcium ionophore A23,187 were examined. Thereafter, the rings were exposed to biotin-fluorescein isothiocyanate-labeled fluorescent or unlabeled leukocytes for 30 minutes. Cell adhesion was quantitated by fluorescent microscopy as well as by scanning electron microscopy. Incubation with n-LDL or ox-LDL did not affect either the contractile or the relaxant response of rings. However, leukocyte adhesion increased markedly in all ox-LDL-treated rings but not in those treated with n-LDL. Thus, leukocyte adhesion occurred independent of NO activity. In keeping with this concept, pretreatment of rings with the NO precursor L-arginine failed to influence leukocyte adhesion to rings incubated with ox-LDL. Treatment of rings with L-NAME also resulted in adhesion of a large number of leukocytes. Furthermore, all rings treated with ox-LDL or L-NAME demonstrated marked expression of P-selectin leukocyte adhesion molecules, determined by immunohistochemistry. Pretreatment of rings with the P-selectin blocking antibody PB1.3 markedly decreased deposition of leukocytes in rings exposed to ox-LDL.(ABSTRACT TRUNCATED AT 250 WORDS)

Background. bcl‐2 protein encoded by the proto‐oncogene bcl‐2 confers to the cell a survival advantage by inhibiting apoptosis. Its aberrant expression has been reported in lymphomas and lung carcinoma. To determine if bcl‐2 plays a role in the gastric carcinogenic sequence, the authors studied bcl‐2 expression in gastric epithelial dysplasia (GED) and chronic atrophic gastritis with intestinal metaplasia (CAG‐IM). Methods. Immunohistochemical staining using monoclonal bcl‐2 protein antibody, clone 124, was performed on archival material. Results. bcl‐2 staining was seen in 13 of 16 GEDs (81%). The staining was heterogenous, suggesting that within the dysplastic epithelium, some cellular clones may have a survival advantage. When noted, the staining in IM was located in the proliferative zone, but some positivity could also be noted higher up along the cellular escalator. Normal gastric mucosa stained in the proliferative zone. Conclusions. The authors demonstrated that bcl‐2 expression is noted in GED as well as in the extended proliferative zone of CAG‐IM. This suggests that prolonged cell survival due to inhibition of apoptosis is instrumental in addition to increased cellular proliferation in the altered cellular homeostasis of the gastric carcinogenic sequence. Whether bcl‐2 protein aberrant expression is an independent process or inherent to immaturity of the cells produced by the increased proliferation awaits further studies. Cancer 1994; 73:2900–4.