Which condition involves a thickening of tissue without an increase in the number of cells?

The condition characterized by a thickening of tissue without an increase in the number of cells is hypertrophy. This occurs when individual cells increase in size, leading to an overall enlargement of the tissue or organ. A common example of hypertrophy can be seen in muscle tissue, where muscle fibers become thicker due to an increase in workload, such as lifting weights.

Hypertrophy specifically refers to the growth of tissue through the enlargement of existing cells rather than through the proliferation of new cells. This distinguishes it from conditions like neoplasm, where there is an abnormal increase in cell number, or atrophy, which involves a reduction in cell size and overall tissue mass. Inflammation may also involve changes in tissue structure but is characterized by increased blood flow and immune response rather than simple thickening due to enlarged cells. Understanding this distinction clarifies that hypertrophy is the correct answer, as it directly describes the increase in tissue mass through the enlargement of existing cells.