TT #117 · Parshas Tazria · Aliyah 2 · Passuk 10
English: It is chronic leprosy on the skin of his flesh, and the priest shall pronounce him impure; he shall not isolate him, for he is impure.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:11
Torah Temimah cites Sifra (Toras Kohanim) for the minimum lesion area needed to accommodate the relevant signs.
Sifra — Vayikra 13, Midrash Sefer
English: Why, then, does Scripture mention white hair and living flesh? It teaches that the lesion must be large enough to receive the signs of white hair and living flesh.
Textual derivation
This unit addresses capacity and size: the lesion must be large enough to accommodate the relevant signs, even where the signs are not both present.