Characterization of tissue and slide artifacts from automated embedding systems.

With recent technological advances and cost reductions, automated embedding systems are rapidly becoming routine in the processing of skin biopsy specimens. The efficiency advantages of this technique are due in part to the use of patented sectionable cassettes that hold formalin-fixed tissue from the time of grossing through tissue sectioning. In this process, the final paraffin block contains both the tissue and the cassette, which are sectioned and stained in unison. Here, we report the multiple tissue and slide artifacts commonly seen with automated embedding systems that are unique to this method of tissue processing. The most frequently observed tissue changes are patterned molding of the biopsy specimen around the cassette material. The most common slide artifacts are due to the presence of geometrically shaped polarizable cassette material adjacent to or overlying the stained tissue. As many of these artifacts strongly resemble the shapes seen in the classic 1980s video game, Tetris, we propose the term of Tetris-like artifacts for these findings. Although we remain confident that use of an automated embedding system does not decrease diagnostic reliability, increased familiarity with the standard appearance of slides processed using this technique will help avoid confusion when evaluating these cases.