Abdominal wall endometriosis in a cesarean scar: a case report

A 25-year-old female Arab patient presented to our hospital with a 1-year history of a stable, nongrowing subcutaneous mass in the right lower abdominal wall adjacent to her Pfannenstiel scar from a cesarean section performed 3 years prior. The mass became increasingly tender during menstruation, prompting evaluation. She reported no prior symptoms of endometriosis, mental health conditions, or relevant family history. Psychosocial assessment revealed no financial, cultural, or linguistic barriers to care. On physical examination, a firm, non-reducible 1.6 cm nodule was palpated at the right edge of the scar without skin discoloration, fluctuation, or size changes during coughing. Abdominal and pelvic exams were otherwise unremarkable. The timeline of her condition began with an uncomplicated C-section (time of hospital visit [T] − 3 years), followed by an asymptomatic mass first noticed at T − 1 year, cyclical pain prompting presentation ( T  = 0), and progression to surgical intervention at T + 2 weeks. Initial ultrasound revealed a well-defined hypoechoic nodule (1.6 × 1 cm) at the scar site, raising suspicion for granuloma or endometriosis. To address diagnostic ambiguity, magnetic resonance imaging (MRI) was performed at T + 1 week, showing a 15 × 12 mm subcutaneous lesion with low T1 and intermediate T2 signals, with no restricted diffusion, and mild contrast enhancement (Figs.  1 , 2 , 3 , 4 ). While imaging favored inflammatory granuloma, the cyclical pain and C-section history kept abdominal wall endometriosis (AWE) high in the differential. Notably, fibromatosis and soft-tissue tumors were considered less likely due to the absence of aggressive imaging features. Fig. 1 Computed tomography scan showing the lesion. Axial, coronal, and sagittal planes are presented, offering comprehensive views of the lesion’s location, size, and characteristics Fig. 2 Computed tomography scan showing the lesion. Axial, coronal, and sagittal planes are presented, offering comprehensive views of the lesion’s location, size, and characteristics Fig. 3 Computed tomography scan showing the lesion. Axial, coronal, and sagittal planes are presented, offering comprehensive views of the lesion’s location, size, and characteristics Fig. 4 Computed tomography scan showing the lesion. Axial, coronal, and sagittal planes are presented, offering comprehensive views of the lesion’s location, size, and characteristics Computed tomography scan showing the lesion. Axial, coronal, and sagittal planes are presented, offering comprehensive views of the lesion’s location, size, and characteristics Computed tomography scan showing the lesion. Axial, coronal, and sagittal planes are presented, offering comprehensive views of the lesion’s location, size, and characteristics Computed tomography scan showing the lesion. Axial, coronal, and sagittal planes are presented, offering comprehensive views of the lesion’s location, size, and characteristics Computed tomography scan showing the lesion. Axial, coronal, and sagittal planes are presented, offering comprehensive views of the lesion’s location, size, and characteristics Due to persistent symptoms, wide surgical excision was performed under general anesthesia at T + 2 weeks. Intraoperative findings included a 30 × 20 × 15 mm firm nodule embedded in fibro-fatty tissue beneath the scar (Fig.  5 ), with no evidence of a hernia. The mass was excised, and the facial defect was repaired primarily. Histopathology confirmed endometrial glands, stroma, hemosiderin-laden macrophages, and fibromyxoid tissue (Fig.  6 ), definitively diagnosing AWE. No malignancy was identified. Fig. 5 This figure shows irregular endometrial-like glandular structures and stroma embedded within fibrous tissue, characteristic of endometriosis. Hemosiderin-laden macrophages are present Fig. 6 This figure shows irregular endometrial-like glandular structures and stroma embedded within fibrous tissue, characteristic of endometriosis. Hemosiderin-laden macrophages are present This figure shows irregular endometrial-like glandular structures and stroma embedded within fibrous tissue, characteristic of endometriosis. Hemosiderin-laden macrophages are present This figure shows irregular endometrial-like glandular structures and stroma embedded within fibrous tissue, characteristic of endometriosis. Hemosiderin-laden macrophages are present Postoperatively, the patient reported immediate resolution of cyclical pain. At her 2-month follow-up (T + 2 months), the incision had healed without complication, and no residual mass was palpable. She was advised to undergo annual gynecologic surveillance for endometriosis recurrence given her surgical and hormonal risk profile.

Endometriosis, a chronic gynecologic condition characterized by the presence of functional endometrial glands and stroma outside the uterine cavity, affects 6–15% of reproductive-aged women globally [ 1 , 2 ]. While classically involving pelvic structures such as the ovaries, uterosacral ligaments, and rectovaginal septum, extra-pelvic manifestations account for 1–12% of cases, with the abdominal wall representing the most frequent extra-genital site [ 3 – 5 ]. Abdominal wall endometriosis (AWE), defined as ectopic endometrial tissue localized between the parietal peritoneum and skin, most commonly arises in or adjacent to surgical scars [ 6 ], Cesarean scar endometriosis (CSE), the predominant subtype of AWE, occurs in 0.03–3.5% of post-cesarean patients [ 7 ]. Anatomically, AWE lesions are categorized as superficial (subcutaneous), intermediate (fascia-infiltrating), or deep (intramuscular) [ 8 ]. Clinically, patients present with cyclical pain; palpable masses; or less commonly, dysuria, dyspareunia, or infertility [ 3 , 9 – 11 ]. Despite its association with prior surgery, scar endometriosis remains under-recognized, with an incidence of 0.03–0.4% following cesarean sections (C-sections), 1.08–2% after hysterectomies, and 0.06–0.7% post-episiotomy [ 12 , 13 ] Diagnostic challenges arise from its nonspecific symptomatology and radiographic overlap with granulomas, hematomas, incisional hernias, abscesses, and soft-tissue neoplasms [ 14 ] Consequently, a high clinical suspicion—particularly in women with cyclical pain and a history of abdominal surgery—is critical to guide timely histopathologic confirmation and intervention [ 15 ] Here, we present a case of cesarean scar endometriosis in a 25-year-old patient, highlighting the diagnostic pitfalls, multimodal imaging findings, and definitive management through surgical excision.

Endometriosis, a chronic and enigmatic condition affecting 6–10% of women of reproductive age [ 1 ], manifests in diverse forms, including extra-pelvic presentations. Cesarean scar endometriosis (CSE), an iatrogenic complication of cesarean section (CS), arises from the implantation of endometrial tissue into surgical incisions, with an incidence of 0.03–3.5%[ 7 ] Our patient, a 25-year-old female, presented with a nodule in the right lower quadrant of her abdominal wall (AWE), the most common extra-pelvic subtype. Despite its prevalence among extra-pelvic cases, AWE remains rare, occurring in < 1% of women with endometriosis [ 8 ]. The lesion localized to the corner of her Pfannenstiel scar—a transverse incision commonly used for CS—aligning with the direct implantation theory. This theory posits that endometrial cells inadvertently transplanted during uterine surgery proliferate under hormonal stimuli [ 4 , 11 ]. Retrospective studies corroborate this anatomical predilection: 77–84% of CSE lesions develop at incision margins, likely due to incomplete removal of endometrial debris during wound closure [ 2 ]. Notably, 80% of post-CS endometriosis cases occur at scar corners [ 2 ], consistent with our patient’s presentation 3 years post-procedure [ 7 ]. While retrograde menstruation, coelomic metaplasia, and immune dysregulation are proposed etiologies, direct implantation remains the most accepted theory for CSE [ 4 , 11 , 16 ]. However, the rarity of CSE despite frequent endometrial exposure during CS underscores a multifactorial pathogenesis. Genetic predisposition, hormonal sensitivity, and surgical technique likely interact to promote ectopic cell survival. Pfannenstiel incisions, though cosmetically favorable, confer higher CSE risk than vertical incisions (24 versus 33 months’ latency) [ 2 , 17 , 18 ]. This disparity may stem from broader dissection planes in Pfannenstiel approaches, increasing tissue contamination and vascular disruption, which facilitate angiogenesis and endometrial cell engraftment. Additionally, cesarean scar defects (CSDs)—myometrial discontinuities from impaired wound healing—create niches for ectopic endometrium. Hormonal fluctuations drive cyclical hemorrhage into these defects, accelerating cyst formation; one reported CSD-associated mass expanded from 4 to 8 cm within a month [ 2 , 7 , 19 ]. CSE mimics granulomas, hernias, and soft-tissue tumors, necessitating multimodal imaging. Ultrasound typically reveals hypoechoic masses, while MRI detects hemorrhagic foci (T1 hypointensity, T2 hyperintensity) and defines lesion depth [ 4 , 20 ]. In our case, MRI identified a 15 × 12 mm subcutaneous lesion in the right iliac fossa with low T1 and intermediate T2 signals, suggesting inflammatory or stitch granuloma. However, imaging limitations persist; histopathology remains the diagnostic gold standard. Transvaginal ultrasound (TVS) and CT aid in evaluating CSD-associated cases, with TVS identifying anechoic “niches” and CT highlighting hemorrhagic components. Although CA125 serves as a biomarker, its negativity does not exclude endometriosis [ 21 ]. Key differentials for AWE include granuloma, fibromatosis, soft-tissue tumors, lipoma, hematoma, sebaceous cyst, incision hernia, and lymphoma [ 22 ]. For our patient, granuloma, fibromatosis, and soft-tissue tumors were considered, with endometriosis prioritized due to surgical history. Histopathology post-excision confirmed a 30 × 20x15 mm nodule with surrounding fat tissue, revealing benign endometrial glands and stroma without malignancy—a critical distinction given reports of rare malignant transformation [ 23 ]. Surgical excision with 1 cm margins is definitive for symptomatic CSE, achieving > 90% symptom resolution [ 2 ]. Medical therapies (e.g., gonadotropin-releasing hormone [GnRH] agonists) offer temporary relief but fail to prevent recurrence. For CSD-associated cases, combined laparoscopic excision and hysteroscopic niche repair optimize fertility outcomes, while postoperative hormonal suppression reduces recurrence risk. Malignant transformation, though rare (57% survival rate), mandates complete resection, emphasizing the need for early intervention [ 7 ]. CSE, though rare, warrants vigilance in women with prior CS presenting with cyclical pain or masses. Pfannenstiel incisions and CSDs heighten risk, necessitating meticulous surgical techniques to minimize endometrial contamination and imaging-guided excision for precise management. Early diagnosis and intervention are paramount to prevent complications, including malignancy, and to improve quality of life. This case underscores the interplay of surgical history, anatomical factors, and hormonal influences in CSE pathogenesis, reinforcing the importance of a multidisciplinary approach in managing this enigmatic condition.