Images – Well-differentiated papillary mesothelioma of the tunica vaginalis

Well-differentiated papillary mesothelioma (WDPM) is a rare mesothelial tumour occurring in the tunica vaginalis of the testicle. The pathological classification of paratesticular mesothelial tumours is controversial and continues to evolve in the literature. Diagnostic criteria of one subtype, WDPM, are histological and include the following: 1) papillary or tubular-papillary architecture; 2) bland nuclear cytology; 3) low mitotic activity; 4) lined by a single row of cuboidal cells; and 5) absence of stromal invasion.1,2 This report presents issues of diagnosis of this rare pathology with imaging from an example case.

Ascus and ascospore development in Eleutherascus peruvianus. 2. Nuclear cytology and early ascus ontogeny

A study was undertaken of the cytological events leading to ascus initiation through delimitation of the ascospores prior to spore wall deposition in Eleutherascus peruvianus Huang. As revealed by Giemsa staining, nuclei in asci which are derived from croziers in the classical manner undergo the three divisions, with each division occurring in a different plane. The result is a globose ascus with eight nuclei displaying a high degree of internal order with respect to the arrangement of the ascospores. Electron microscopy reveals that subsequent to the final nuclear division, the ascus becomes filled with several elongate segments of double membrane underlying the ascus plasmalemma. These membrane segments appear to result from marked focal invaginations of the ascus plasmalemma and ultimately fuse together to form the ascus vesicle. Occasional observations of nuclei outside of the ascus vesicle membranes are believed to account for the often observed phenomenon of asci with odd numbers of ascospores. The significance of these findings relative to those for some close allies is discussed.