Aims-To investigate the immunohistochemical staining of normal, hyperplastic, and neoplastic adrenal cortex with a monoclonal antibody against inhibin. Also, to determine whether immunostaining with this antibody is useful in diVerentiating between adrenal cortical neoplasms and other tumours involving the adrenal gland that might mimic them. Methods-Normal adrenal tissue (n = 20) and specimens from cases of adrenal hyperplasia (n = 13), adrenal cortical adenoma (n = 15), adrenal cortical carcinoma (n = 4), phaeochromocytoma (n = 8), and adrenal metastatic tumour (n = 7) were stained with a monoclonal antibody against the subunit of human inhibin. Results-Positive staining with the antiinhibin monoclonal antibody was seen in all normal adrenal glands. Immunoreactivity was largely confined to the inner cell layers of the adrenal cortex, with no staining of the adrenal medulla. All hyperplastic adrenal glands and adrenal cortical adenomas and carcinomas were also immunoreactive. The other tumours studied were negative. Conclusions-There is consistent immunoreactivity with the anti-inhibin monoclonal antibody in normal adrenal cortex and in hyperplastic and neoplastic adrenal cortical lesions. In the normal adrenal cortex, positive staining is mainly confined to the zona reticularis. Other neoplasms involving the adrenal gland are negative. Immunohistochemical staining with anti-inhibin monoclonal antibody, performed as part of a panel, may prove to be of value in the distinction between adrenal cortical carcinoma and phaeochromocytoma or metastatic tumour. (J Clin Pathol 1998;51:114-116)

Gastrointestinal stromal tumours are lesions in which it is difficult to predict clinical outcome from the histological appearances. Sixty cases were studied using three different methods of assessing aspects of cellular proliferation; these were (i) immunostaining for proliferating cell nuclear antigen (PCNA), (ii) interphase nucleolar organizer region staining (AgNORs), and (iii) a histological grading system based on mitotic counts. Both PCNA immunostaining and AgNOR counts were found to correlate well with histological grading and all three methods independently showed good correlations with survival. This suggests that these proliferation-associated markers may be used as additional features to support histological grading in this relatively uncommon group of tumours.

Bone marrow trephine biopsies are routinely performed, in conjunction with marrow aspirates, in the investigation of patients with a variety of haemopoietic disorders, both neoplastic and non-neoplastic. Trephine biopsy specimens are particularly useful where there is significant bone marrow fibrosis which frequently results in an inadequately aspirated specimen or "dry tap". Trephine biopsy specimens are also useful in the assessment of marrow cellularity and in the determination of the extent of marrow involvement by neoplastic or other infiltrates. The relation between cellular elements and normal marrow structures, such as bony trabeculae and blood vessels, can be assessed accurately only on bone marrow trephine biopsy specimens. In addition focal lesions, such as granulomas, are more readily identifiable on trephine biopsy specimens than on marrow aspirates.Two main methods are used for the routine histological examination of bone marrow trephine biopsy specimens, namely paraffin wax embedding followed by decalcification and plastic embedding followed by the cutting of 1 ,um sections. A third approach to processing such specimens is the use of cryostat sections of undecalcified bone marrow biopsy specimens. This method, although allowing for optimal antigen preservation, results in very poor cellular morphology, a serious obstacle in evaluating these specimens, and thus has not gained widespread acceptance. Problems arise in cutting sections of bone marrow trephine biopsy specimens because of the intimate mixture of hard tissue (bone) and soft tissue (marrow and fat). To cut adequate intact sections, one can either make the tissue uniformly soft by paraffin wax embedding followed by decalcification, or make the tissue uniformly hard by using a plastic embedding procedure. There has been much debate in the literature regarding the relative merits of these two techniques.`'7 Those who advocate paraffin wax embedding of trephine biopsy specimens stress the advantages of the familiarity of most pathologists with sections cut from such material combined with their unfamiliarity with plastic embedded sections and the fact that widespread antigen preservation allows a wide range of immunohistochemical reactions to be performed.'2 Furthermore, plastic embedding represents a significant departure from normal routine for the diagnostic histopathology laboratory as special equipment, different preparation protocols