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A prospective electron microscopic study, incorporating blind controls, demonstrated tubuloreticular structures (TRS) in the buffy coat lymphocytes of 32 patients with connective tissue disease. From 1 to 8% of the lymphocyte sections were involved. The abnormal structures consisted of interwoven, electron-dense tubules (220 to 280 A diameter) which were located within the endoplasmic reticulum. Tubuloreticular structures were found in lymphocytes from 20 of 30 patients with systemic lupus erythematosus (SLE), 2 of 4 with discoid lupus erythematosus, 8 of 20 with other connective tissue disease and none of 22 control cases. Clinical evaluation of the patients with SLE disclosed no specific differences between those with TRS-positive or TRS-negative lymphocytes; there were some indications of greater disease activity in the TRS-positive group. The biologic nature of TRS is unknown, but they have been linked to virus infection under both clinical and experimental conditions. systemic lupus erythematosus (SLE) (3-6) and many patients with related diseases of connective tissues (7-9). We now report a significant frequency of morphologically identical structures in the circulating lymphocytes of such patients.T h e tubules in question have been distinguished by their ultrastructural appearance. They are relatively electron-dense and measure in the range of 220 to 280 A in diameter. They are interwoven within membrane-limited compartments which can often be identified as dilatations of the endoplasmic reticulum or perinuclear space. T h e biologic nature of these structures is still unknown, and we have adopted the description tu buloreticular struclures (TRS) also proposed by Dalton (1 0).T h e possibility of finding T R S in circulating cells was suggested by electron microscopic examination of a skin biopsy from a 24-year-old man with SLE with subcutaneous nodules and histologic evidence of chronic vasculitis. Thin

No abstract

Ultrastructural examination of 26 osteogenic sarcomas has revealed that in addition to the basic osteoblast comprising the tumor, five additional cell types may be identified. These include chondroblasts, osteocytes, undifferentiated cells and myofibroblasts. The latter cell type has not been reported in previous studies of medullary osteosarcomas. The relative portions of the cell types varied as to the type of osteogenic sarcoma studied. Osteoid production, the single diagnostic feature of these tumors, was evident and the various ultrastructural appearances of this material are shown. One case of an osteogenic sarcoma that arose in Paget's disease of bone is described and did not differ ultrastructurally from the conventional medullary osteogenic sarcoma. Our studies have shown that osteogenic sarcoma may share common ultrastructural features with other sarcomas involving bone and soft tissue and that the basic difference between osteogenic sarcoma and soft-tissue sarcomas is the presence of osteoid in the former and differing cytoplasmic differentiation in the latter category of tumors.