Types KS lesions are divided into three groups by appearance, with much overlapping.
• Nodular lesions are of varying size and thickness. They are purple and will at times have a halo of brown or
yellow pigment around them.
• Infiltrating lesions may be quite large, may be raised and grow downward beneath the skin.
• Lymphatic lesions may mimic other causes of swollen lymph nodes and may require a biopsy to rule out
infection.
To a pathologist looking at a biopsy under the microscope, all three types of KS appear similar. Three sub-types have been identified, all of which are treated much the same. Clinically, the spindle cell variety is the slowest growing, the anaplastic is the most aggressive, and the mixed cell has a somewhat intermediate growth rate.
How It Spreads Most malignancies arise in one area, perhaps in one or a small group of cells . As the tumors grow, there comes a time when they spread either by direct invasion or through the blood or lymphatic systems. But KS often appears simultaneously in many sites. This suggests that there is a causal agent, possibly in the blood, that triggers the formation of the lesions in several areas. In this, KS bears a strong resemblance to some viral "rash" diseases, like measles and chicken pox. As the lesions grow, they fuse together, thicken and may protrude from the skin or ulcerate.
