Case for the Panel:Microtubules in Plasma Cells

Abstract

Dear Sir: While studying a routine kidney biopsy, we encountered these very interesting bundles of microtubules in the endoplasmic reticulum of several interstitial plasma cells. The biopsy was from a 63-year-old male who presented with hematuria. Histologically, the glomeruli showed the features of chronic glomerulonephritis and numerous plasma cells were noted in the interstitium (Fig. 1). Several normal (Fig. 2) and atypical plasma cells with well-developed centrosomes (Fig. 3) were seen at electron microscopic level. Occasional plasma cells exhibited early microtubule formation (Fig. 41, while most showed cytoplasm filled with dilated rough endoplasmic reticulum containing profiles of both longitudinally and cross-sectioned microtubular bundles (Fig. 5). A high-power view of these structures (Fig. 6) clearly demonstrates their crystalline arrangement, Groups of 10-24 microtubules, measuring 12-1 5 nm in cross-section, were counted in single bundles. Fine bridges are discernable between the microtubules on crosssection, but not on longitudinal section (Fig. 7). Straight or rodlike microtubules have been reported in the endoplasmic reticulum of cells in various lesions.' Could these microtubules represent a distorted form of e I a b o r a t i o n of i rn m u n og I o b u I i n s ? We would very much appreciate the panel's opinion.