What appears below is an endeavor to correct errors conceptually that punctuated a chapter in the textbook titled, Neoplasms with Follicular Differentiation undertaken by me in conjunction with Vijaya Reddy and Peter Soyer, and published in 2001. The chapter was the very last one in that tome of 1109 pages and it appeared, by itself, alone, in a separate section headed, "Malignant proliferation with simulation of follicular differentiation," the reason for that decision being our thesis then that the neoplasm under consideration truly was a "Proliferating tricholemmal cystic squamous-cell carcinoma" (in fact, that was the very caption of the chapter itself) that did not develop in a pre-existing tricholemmal (isthmic-catagen) cyst and that did not differentiate along tricholemmal (isthmic-catagen) lines. All of that was dead wrong. In the piece that follows, we seek earnestly to right all that was wrong.

In order to gain most from the essay that follows, a reader is encouraged to begin by studying each of the series of photomicrographs and the legends to them (Figures 1–14).