Partial myoepithelial differentiation is common in simple epithelial hyperplasia (epitheliosis) of the breast but functional myoepithelial differentiation with basement membrane production is exceedingly rare. A peculiar change of hyaline globules within benign epithelial hyperplasia has been recognised before as "collagenous spherulosis" and type IV collagen has been shown by immunohistochemistry. Another seven cases are described which show the presence of laminin and collagens IV and III within the proliferation. Electron microscopical examination of two cases using material retrieved from the wax block showed varying degrees of myoepithelial differentiation of the cells immediately surrounding the spherules and basal lamina material, including mature collagen fibrils in one case. The degree of myoepithelial differentiation of the cells surrounding the spherules seemed to correlate with the differing types and amounts of extracellular matrix in the spherule.Histopathologists should be aware of this rare change as it may be misinterpreted as in situ carcinoma. In 1987 Clement, Young, and Azzopardi described a peculiar change within the lumina of breast acini and ductules which they designated "collagenous spherulosis".l This change had been noted in referral material where it had occasionally been confused with malignancy, especially adenoid cystic carcinoma, and in archival material. The authors of this paper were able to show that the hyaline material within the intraluminal space was rich in collagen by conventional histochemistry, and in a subsequent letter they were able to show one component of basement membrane by immunocytochemistry.2 We present a further seven cases with immunohistochemical results showing the varying proportions of basal lamina proteins and interstitial collagens in the spherules. In two cases this was confirmed by ultrastructural examination of tissue taken from the paraffin wax blocks.

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In late June 2007, the Epidemiological Surveillance Network in Castilla y León, northern Spain, reported a series of cases in a rural area in the province of Palencia and in the provincial capital city of León, labelled as “fever of unknown origin”. Subsequent epidemiological investigation confirmed an outbreak of tularaemia.

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