MON-436 Cribriform-morular Variant of Papillary Thyroid Carcinoma: A Case Report

Background: Cribriform - morular variant is a rare variant of papillary cancer with 1–2 % prevalence. There are no established guidelines to screen for thyroid cancer in patients with APC gene mutations and FAP. We present a case of a young female with APC gene mutation and thyroid cancer. Case: Female, 25 years-old, without anemia, underwent colonoscopy at age 22 and multiple polyps were seen. One polyp showed intramucosal carcinoma with high-grade dysplasia. She was diagnosed with FAP. She was found to have APC gene mutation on genetic analysis. No family history of FAP was reported. Chest and abdominal CT showed multiple thyroid nodules. Thyroid ultrasound showed 3 nodules. The largest is in the mid R lobe, measuring 1 cm, and is isoechoic to hypoechoic, containing some small central cystic areas. The nodules in the left lobe measure 0.6 and 0.7 cm. FNA of the right thyroid nodule showed follicular neoplasm. Afirma was suspicious. She underwent total thyroidectomy. Pathology report showed multifocal tumor in both right (0.8 cm) and left lobe (0.5 cm). Histologic type was Papillary carcinoma, cribriform - morular variant. All surgical margins were negative. No angio-lymphatic invasion or extra thyroidal extension was identified. Pathologic stage classification was m pT1a pN0 pM0. Patient did not receive RAI ablation. Patient doing well and no further recurrence of thyroid cancer is noted. Discussion: Patients with FAP have a greatly increased risk for colorectal cancer and also have an elevated risk for other cancers including thyroid cancer (1%-2% compared to 1% in general population). According to ACG guidelines of 2015, annual thyroid screening by ultrasound should be recommended to individuals affected with FAP. Additionally, thyroid cancer found in unscreened patients with FAP was more advanced as compared to patients screened for cancer requiring less aggressive approaches. On ultrasonography, most nodules had benign-looking features (well-defined, hypoechoic, oval to round shapes without calcification), but some nodules had capsular invasion and larger height: width shape. In preoperative FNA, they were diagnosed as CMV-PTC/PTC but could also present as follicular neoplasm or PTC-follicular variant. Compared to conventional PTC, CMV-PTC had a lower frequency of lymph node metastases at presentation (12%) and distant metastases (3%) as well as lower recurrence rates (8.5%) and patient mortality rates (2%). Physical exam and clinical history is not sufficient to screen for cancer. In patients with APC gene mutations and FAP, there should be high suspicion for diagnosing thyroid cancer as the nodules are usually benign looking and small in size. As noted in the case, nodules were found incidentally, and tumor size was small with benign looking nodules. Additionally, screening should be focused more on young females below the age of 35 because of the high prevalence of cancer.