The higher risk of VTE with oral estradiol can be attributed to the first pass and a disproportionate effect on liver synthesis of coagulation factors. Even high doses of parenteral estradiol, such as high-dose polyestradiol phosphate, have minimal influence on coagulation factors, in contrast to oral estrogen therapy. However, sufficient doses of parenteral estradiol, for instance very high doses of estradiol valerate by intramuscular injection, can nonetheless activate coagulation, presumably increasing VTE risk.In addition to the route of administration, the type of estrogen influences VTE risk. Oral conjugated estrogens are associated with a higher risk of VTE than oral estradiol. Estradiol- and estradiol valerate-containing birth control pills are associated with a lower risk of VTE than birth control pills containing ethinylestradiol. The relative risk of VTE is thought to be highest with oral ethinylestradiol, intermediate with oral conjugated estrogens, low with oral estradiol and parenteral estradiol valerate, and very low with transdermal estradiol. Conjugated estrogens and ethinylestradiol are thought to have a higher risk of VTE than estradiol because they are resistant to hepatic metabolism and have a disproportionate influence on liver production of coagulation factors.The combination of oral or transdermal estradiol and a progestin is associated with a higher risk of VTE than estradiol alone. Dydrogesterone is associated with a lower risk than other progestins such as medroxyprogesterone acetate and norethisterone, while oral progesterone is associated with no increase in risk of VTE.
Trichilemmal carcinoma  is a cutaneous condition reported to arise on sun-exposed areas, most commonly the face and ears. : 674

See also
Trichilemmoma
Skin lesionA similar tumor, although in the nail bed, is called onycholemmal. References


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