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Notes: Aims:  Polymorphous low-grade adenocarcinoma of the minor salivary glands is an infiltrative neoplasm characterized by bland-looking tumour cells arranged in diverse architectural patterns. It is considered to be of low-grade malignant potential in that nodal metastases are seen in only a minority, and distant spread is rare. Even more unusual is the transformation of polymorphous low-grade adenocarcinoma to a histologi-cally high-grade carcinoma, i.e. dedifferentiation. In this paper, we describe the clinicopathological and immunohistochemical findings in two further examples.Methods and results:  Two patients presented each with a tumour of the palate. Histopathological examination showed the typical morphological, cytological and immunohistochemical features of a polymorphous low-grade adenocarcinoma. In one case there was a second component of high-grade carcinoma showing nuclear atypia, markedly increased mitotic activity and MIB1 index, as well as prominent zones of necrosis. It expressed epithelial markers and androgen receptors, and thus resembled salivary duct carcinoma. Similar tumour tissue was observed in one of the cervical nodal metastases, which was biopsied at the same time as the palate. In the second patient, a high-grade component was discovered when the tumour recurred in the palate 13 years after the initial biopsy. Whilst morphologically similar to that in first case, there were significant immunohistochemical differences such as retention of some of the polymorphous low-grade adenocarcinoma profile and absence of androgen receptor expression.Conclusions:  Polymorphous low-grade adenocarcinoma was first described relatively recently, and as experience with it continues to accumulate, it is becoming clear that late recurrences and metastases, whilst still infrequent, may not be quite as rare as previously thought. Reports of histological transformation are even scarcer, and most occurred at least 13 years after the polymorphous low-grade adenocarcinoma was initially recognized. It is a real possibility that this phenomenon, like clinical progression, may also be encountered more often as time passes. Therefore, we believe that, whilst polymorphous low-grade adenocarcinoma is certainly far less aggressive than, for example, adenoid cystic carcinoma, it nevertheless remains a true malignancy with a potential to prove fatal in a minority of patients.

Notes: Aims : Non-invasive carcinoma ex pleomorphic adenoma is defined as a carcinoma arising within the boundaries of a pleomorphic adenoma (PA), but which fails to display invasion beyond the capsule of host PA. Alternative names are intracapsular, in situ, or focal carcinoma. The true nature of non-invasive carcinoma ex-PA is still controversial; for example, it is not clear whether it represents early but genuine carcinomatous changes with the genetic make-up of malignant cells, or simply cytological, possibly metaplastic or ‘bizarre’ changes in PA. Strong overexpression and amplification of HER-2/neu protein has recently been demonstrated in invasive carcinoma ex-PA. In addition, data from breast cancer studies suggest that amplification of HER-2/neu and overexpression of its gene product is mainly involved in the initiation of breast oncogenesis. We sought to establish whether this method could help to demonstrate that what is described as non-invasive carcinoma ex-PA is really a genuine malignancy, albeit in an early phase.Methods and results : Eleven cases of non-invasive carcinoma (in situ) ex-PA were studied for HER-2/neu status using immunohistochemistry and fluorescent in-situ hybridization (FISH). Cells of focal non-invasive carcinoma ex-PA were strongly positive for HER-2/neu protein, while the cells of the maternal PA were always negative. Two cases of low-grade non-invasive myoepithelial carcinoma ex-PA were negative. In four cases out of a total of six tumours studied by FISH, we detected amplification of HER-2/neu gene signals in tumour cells of focal, non-invasive, carcinoma.Conclusions : The current data suggest that non-invasive carcinoma ex PA is a genuine carcinoma within a PA. However, the presence of cyto-nuclear atypia is not sufficient to make a definite diagnosis of malignant change, which requires a combination of morphology and immunohistochemistry.

Notes: Abstract Primary malignant non-Hodgkin's lymphomas account for 0.4% of malignant neoplasms arising in the bladder and female urethra, but do not comprise a uniform group, and three subgroups can be identified which account for a majority of cases. The most common is a low-grade B-cell lymphoma similar to neoplasms arising in the mucosa-associated lymphoid tissue at other sites — so-called ‘MALTomas’. These generally display indolent behavior. A second group accounting for approximately one-fifth of cases is composed almost entirely of large lymphoid cells, and these tumors have a poor prognosis. A third possible group comprises only a few patients who present with diffuse thickening of the bladder wall, and have a poor prognosis. The authors present a new case which suggests that this latter group may be of T-cell origin. In addition to these three subtypes, others no doubt await recognition. The different forms of primary lymphoma appear to require different treatments, and some guidelines are proposed.

Notes: Summary The probabilistic approach to tropical cyclogenesis is advanced here by examining the role of convection in the early stages. The development of “hot towers”, that is tall cumulonimbus towers which reach or penetrate the tropopause, and their role in tropical cyclogenesis is investigated in two well-documented cases of formation. namely hurricane Daisy (1958) in the Atlantic and Tropical Cyclone Oliver (1993) in the Coral Sea. The hot towers in Daisy had been intensively studied by Malkus and Riehl three decades ago but remained mainly unpublished. The dynamics of Oliver genesis by merging mesoscale vortices has been recently reported, but much of the aircraft data remained. This paper adds the evolving contribution of cumulus-scale events and their associated electrification, which was made possible by the addition of an electric field mill, a numerical cloud model and other remote sensors. In their genesis stages, Daisy and Oliver appeared very different because Daisy resulted from a deepening tropical wave in the Atlantic and the pre-Oliver vortex emerged eastward from the Australian monsoon trough. However, the vertical profiles of θE in the rain areas were nearly identical, with the characteristic concave shape showing substantial midlevel minima. Therefore, both required increasing upflux of high θE subcloud air in order to accomplish the formation stage, with about two hot towers each in the nascent eyewall. In both cases, partial eyewalls developed at the edge of the convection, permitting subsidence in the forming eye, which was shown to contribute to the pressure fall. The probabilistic concept proposes that any contribution to early pressure fall raises the probability of success. When the incipient storm goes through those fragile phases more rapidly, the risk of death by the onset of unfavorable large-scale factors such as wind shear or upper-level subsidence is reduced. Daisy developed in an inactive, moist environment with light, variable winds throughout the troposphere while in Oliver, strong divergent upper outflow apparently outweighed strong wind shear, although the latter was responsible for a slow and messy development of a closed, circular eye. In both storms, the hot towers in the major rainband were taller and stronger than those in the early eyewall. Onedimensional time-dependent model runs were used to simulate both in Oliver with two important results: 1) the taller rainband clouds permitted greater high level heating, if it could be retained; and 2) greater electrification and more lighting occurred in the rainband although the partial eyewall clouds also showed strong electrification. Airborne radar, electrification measurements and models are fitted together to understand their relationship. An important result is the clear inference that fairly deep mixed phase regions existed in both eyewall and rainband, in which the DC-8 aircraft experienced liquid water at temperatures colder than −40°C below freezing. These results show that the claims of no supercooled liquid water in tropical cyclones require re-examination with the proper measurements of electricification that are now feasible.

Notes: Summary We examine a family of tall (up to 20 km) cumulonimbus complexes that develop almost daily over an adjacent pair of flat islands in the Maritime Continent region north of Darwin, Australia, and that are known locally as “Hectors”. Nine cases observed by a rawinsonde network, surface observations (including radiation and soil measurements), the TRMM/TOGA radar, and one day of aircraft photography are used to analyse the development, rainfall, surface energy budgets, and vertical structure of these convective systems. The systems undergo convective merging which is similar to that observed in previous Florida studies and is multiplicative in terms of rainfall. About 90% of the total rainfall comes from the merged systems, which comprise less than 10% of convective systems, and this has implications for the manner in which tropical rainfall is parameterised in largerscale numerical models. By comparison to the West Indies, GATE, and Florida, the Hector environment contains a weaker basic flow, with less vertical shear. The main thermodynamic difference is that the Darwin area has an unstable upper troposphere and very high tropopause. Numerical modelling results support earlier observations of updraughts in excess of 30 ms−1 in this region, but show that only modest convective drafts are experienced below the freezing level (5 km). The surface fluxes over the islands are estimated from a Monash University study to be mainly in latent form from evapotranspiration, with a Bowen ratio only slightly larger than that commonly observed over oceans. These surface fluxes are crucial to the development of a suitable mixed layer to support deep convection. The flux estimates agree with the observed changes below the cloud base and provide sufficient information for calculations of the bounds on precipitation efficiency. Of particular interest are the observations of Hector development on a day when the islands were under a dense cirrus overcast. We find that the islands still provide sufficient net sensible and latent heat fluxes to initiate convection.