Osteosarcoma is the most common primary malignant tumor of the skeleton involving predominantly metaphysis of the long bones. Diaphyseal osteosarcoma is a rare form, which accounts for approximately 10% of all cases of osteosarcomas. Osteosarcoma contains a family of lesions with considerable diversity in histologic features and grade. We present a case of a 29-year-old male with diaphyseal osteosarcoma of the left tibia, who presented with pain and swelling over middle one-third of the left leg. The biopsy of the lesion revealed varied histomorphologic features in a small tissue studied. This prompted us to report the various histologic patterns of osteosarcoma.