Low-Grade Appendiceal Mucinous Neoplasm (LAMN) Primarily Dia
Low-grade appendiceal mucinous neoplasms (LAMN) are detected in 0.7 to 1.7% of all appendicectomies. The diagnosis can be challenging, particularly in female patients where the differential diagnosis of primary appendiceal and ovarian mucinous neoplasms is unclear. A 71-year-old female was referred to the Gynecological Department with the diagnosis of a right ovarian cystic tumor. The lesion was identified through a transvaginal ultrasound performed for vague lower abdominal pain symptoms that had started a month prior. Findings from the routine laboratory examinations were unremarkable, and all tumor markers were within normal range. The patient had received a screening colonoscopy six months prior without any pathologic findings. Her medical history included hypertension, hypothyroidism, and depression.

A Multidetector Computer Tomography (MDCT) was conducted for further evaluation of the findings. A low-attenuation cystic lesion, with asymmetric wall thickening and focal calcification, was identified in the anatomic region of the right iliac fossa, measuring 3.3 × 6.5 cm. CT was in concordance with the previous reports and confirmed that the tumor originated from the right ovary. Peritumoral ascitic fluid was also detected. Distal metastases or pathological regional lymph nodes were not identified. Thus, the patient was scheduled for surgical treatment. Intraoperatively, with a midline subumbilical incision, a distended appendix, with an intact thick wall and without any inflammatory signs, was identified. Macroscopically, there were no signs of distal metastasis or tumor deposits. Additionally, no pathological findings were identified in the ovary. Following the expansion to a midline incision for better visualization, a decision was made to perform a right hemicolectomy, and the tumor was excised unruptured. The patient had an uneventful recovery; oral feeding began on the 3rd postoperative day, and the patient was discharged on the 9th postoperative day.

A microscopic examination of the specimen revealed a gross dilatation of the appendix measuring 6.5 × 4.5 × 4 cm with abundant mucin in the lumen. Normal morphological characteristics of an appendix were not recognized (Figure 3). Microscopic examination showed replacement of the normal appendiceal epithelium by mucin-producing columnar glandular epithelium with low-grade dysplasia. The lining was flat with few areas of villous architecture. There was fibrosis of the underline wall with scattered residual smooth muscle fibers throughout the caecal wall. There were no histological findings of conventional, high-grade mucinous appendiceal adenocarcinoma, such as the proliferation of mucinous epithelial cells with high-grade dysplasia, architectural complexity, cribriform pattern, or glands infiltrating in a desmoplastic stroma.