Cribriform-morular variant of papillary thyroid carcinoma with poorly differentiated features: report of a case and review of the literature

Introduction Cribrifrom-morular variant of papillary thyroid carcinoma (CMVPTC) is an uncommon thyroid neoplasm that occurs predominantly in women and is sometime associated with familial adenomatous polyposis (FAP). Some of these tumors may undergo dedifferentiation to poorly differentiated thyroid carcinoma (PDTC). We describe a rare case of this carcinoma in a women without a history of FAP. Case presentation A 49-year-old woman with a history of breast carcinoma presented with a thyroid mass. A CMVPTC was diagnosed after excision. There was no history of FAP. Histological examination showed classical features of CMVPTC in most areas, but about 20% of the carcinoma showed features of a poorly differentiated carcinoma with a solid pattern of growth, increase mitotic activity and a high Ki-67 proliferative index (25%). Immunohistochemical stains were positive for nuclear and cytoplasmic beta catenin staining. These special studies supported the diagnosis. Conclusion CMVPTC with dedifferentiation to PDTC is a rare carcinoma with only 4 previous documented cases in the literature. This aggressive variant of thyroid carcinoma is more common in females, as is CMVPTC, and is often associated with an aggressive biological course. The cases usually express nuclear beta catenin and estrogen, progesterone and androgen receptors have been reported in some cases. Some cases may have somatic alterations of the APC gene and TERT promoter mutations. These carcinomas may metastasize to lung, bones and lymph nodes. Because of its aggressive behavior, patient with this diagnosis should be treated aggressively to control disease spread and mortality from the carcinoma.

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.