Many diseases carry the name of a person. In the past,it was considered proper to specify eponymous diseases using the possessive form. For example, Hodgkin's lymphoma, Kaposi's sarcoma, Warthin's tumor, and so on. More recently, the fashion has been to use the non-possessive surname. During a 1975 meeting to standardize the nomenclature of malformations, a recommendation was made to use "Down Syndrome" not "Down's Syndrome." The argument was made that "The possessive use of an eponym should be discontinued, since the author neither had nor owned the disorder" . The same applies to neoplasms, and the non-possessive form of eponymous tumors is should probably be used (e.g., Hodgkin disease or Hodgkin lymphoma, Kaposi sarcoma, Warthin tumor).
More confusing, to my mind, is the incosistent way we deal with adjectival forms of eponymous terms.
So, it's Brownian motion (not Brown's motion or Brown motion), and Abelian groups (Not Abel's groups or Abel groups) and Darwinian evolution (not Darwin's evolution or Darwin evolution).
In medicine, it gets even weirder. For example, consider the adjective, "Kaposiform". There are at least two "Kaposi" disorders. Kaposi sarcoma (an angiosarcoma most often seen nowadays in immunosuppressive syndromes) and Kaposi varicelliform eruption, a now rare complication of vaccinia superimposed on atopic dermatitis with high fever and generalized vesicles and papulovesicles. We use the word "kaposiform", but what exactly could this word mean given the mutliple conditions associated with the name "Kaposi?"
Another strange adjective, used by pathologists, is rubriform, meaning red. Red is a color, not a form. So rubriform is an inconsistent metaphor within a single word. Some might prefer the term "reddish," but I doubt that reddish is really a word. It seems to me that the word "red" should suffice when "reddish" or "rubriform" would only confuse.
1. Committee report. "Classification and nomenclature of morphological defects (Discussion)". The Lancet 305:513, 1975.