Scar Endometriosis with Rudimentary Horn: An Unusual and Elucidative Report of a Case Diagnosed on Histopathology and Immunohistochemistry

Endometriosis is defined as the presence of functioning endometrial tissue outside the endometrial cavity. Scar endometriosis, also known as spontaneous abdominal wall endometriosis, is an unusual clinical presentation which often goes unnoticed. It usually develops after pelvic operations. The incidence has been estimated to be only 0.03%–0.15% of all cases of endometriosis. It can be either asymptomatic or present as abdominal wall pain at the site of surgical incision. It is most commonly diagnosed clinically or on ultrasonography. The treatment of choice predominantly remains surgical excision. We present a case of a 24-year-old female (known case of bicornuate uterus) who presented with chief complaints of abdominal pain for 1 month and 6 months after metroplasty. The patient was clinically diagnosed as a case of scar endometriosis with rudimentary horn and fistulous tract and taken up for surgery. Both the scar tissue and fistulous tract were removed and histopathology revealed only endometrial glands without stroma or hemosiderin-laden macrophages. Diagnosis of scar endometriosis was established on positive immunohistochemistry for estrogen and progesterone receptor in endometrial glands. Timely diagnosis and surgical excision of scar endometriosis along with close follow-up are necessary to prevent complications and recurrence.