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Objective: Our purpose was to identify patterns of uterine innervation in normal uteri and selected clinical conditions including adenomyosis and chronic pelvic pain., Study Design: A retrospective survey was performed of stored uteri removed at hysterectomy for a variety of clinical conditions, including 8 uteri from nulliparous subjects (group 1, mean age 40.0 years, range 30-52 years), 21 uteri with no reported histologic abnormality from multiparous subjects (group 2, mean age 43.4 years, range 32-53 years; mean parity 2.0, range 1-4), 31 uteri reported with adenomyosis (group 3, mean age 42.4 years, range 29-54 years; parity 2.0, range 0-4), and 17 uteri from subjects with pelvic pain (group 4, mean age 39.1 years, range 30-52 years; parity 2.5, range 1-7). Sections were cut from paraffin blocks of the isthmus of stored uteri (in the majority of cases) and stained with protein gene product 9.5 to identify nerves. Sections of pancreas provided positive controls. Each section was reviewed by two unblinded observers., Results: Group 1 (n = 8, nulliparous uteri) showed significant nerve bundles at the endometrial-myometrial interface and in the subserosal layers, with nerve fibers noted in intervening neurovascular bundles supplying the myometrial stroma. Group 2 (n = 21, histologically normal uteri from parous subjects) showed patterns of innervation similar to those of group 1 with the exception that 6 uteri demonstrated areas of nerve fiber proliferation (see below, group 4). In group 3 (n = 31, uteri with adenomyosis), 30 uteri (30/31) showed large areas of myometrium without nerves and absence of nerves in the neurovascular bundles supplying these areas. Five uteri showed areas of nerve fiber proliferation at the margins of the adenomyosis. Subserosal nerves were present in the majority of these uteri. In group 4 (n = 17), uteri were removed for chronic pelvic pain. Eleven uteri demonstrated proliferation of small-diameter nerve fibers throughout the myometrium; in 6 uteri there was asymmetry of nerve fiber proliferation., Conclusions: Variations in uterine innervation were noted in the isthmic region of uteri stored after hysterectomy. Uteri with adenomyosis frequently demonstrated large areas with absence of nerve fibers; uteri from subjects with chronic pelvic pain showed proliferation of small-diameter nerve fibers throughout the myometrial stroma. Nerve fiber proliferation was asymmetric in some of these specimens.