Objective To study the clinicopathologic features of thyroid-like follicular renal cell carcinoma.Methods Clinical data were collected in 5 cases of thyroid-like follicular renal cell carcinoma.HE staining and immunohistochemistry were carried out in surgically-removed specimen to analyze the clinical and pathological features with review of the literatures.Results The patients aged 20-55 years, with one male and four females;the tumor occurred in the left kidney in three cases and right kidney in two cases.One case had a history of thyroid papillary carcinoma 3 years ago, and the patient had left flank pain, macroscopic haematuria for 2 weeks.The rest four cases had no consciousness of clinical symptoms and signs, without history of thyroid gland surgery; the physical examination found a mass in the kidney and normal thyroid glands.Three patients underwent radical nephrectomy, and the other two patients underwent tumor partial nephrectomy.The tumors were 2-4 cm in size.They showed a solitary nodular mass of well circumscribed with taupe and gray on cut surface.Microscopically,most of tumor cells arranged in thyroid follicular pattern in different sizes, with papillary configuration in a small portion,in four cases;the follicular structure was intermixed with the papillary each half in one case.A large amount of thyroid colloid was deposited within follicule-like structure or papillary axis, lined by simple columnar cells or cubic cells, with obvious atypia, ground-glass nuclei, nuclear groove and rare mitosis.Immunohistochemical staining showed tumor cells were positive for PAX8,and negative for thyroid transcription factor 1 (TTF1) and thyroglobulin ( Tg).One of five patients presented with lymph node metastases (4/4) of renal hilum the same time in the diagnosis.Five cases were followed up for 5 -84 months after operation, and no tumor progression was found.Conclusions Thyroid-like follicular renal cell carcinoma is primary renal epithelial malignant tumor.The diagnosis mainly depends on its characteristics of histological appearance,namely similar to the histological morphology of well-differentiated thyroid follicular carcinoma and papillary carcinoma, and the metastasis from the thyroid papillary or follicular carcinoma must be excluded.On the premise of clinical history, immunohistochemical markers TTF1 and Tg have certain value in the differential diagnosis.

Objective:To investigate the clinicpathological, immunohistochemical and molecular genetic features of malignant mixed mesodermal tumor (MMMT) in the female reproductive system.Methods:To analyze its histopathological characteristics, we performed a retrospective review of the MMMT cases diagnosed at PLA General Hospital, Beijing, China during 2005-2019 using its surgical and pathological databases. EnVision immunohistochemical staining was used to detect the expression of ER, PR, p16, p53 and MMR proteins.Results:Fifty cases were conformed to the diagnosis, including 29 cases originated in the uterus, 16 cases in ovary, 4 cases of synchronous occurrence in uterus and ovary, 1 case in cervix. The tumor was histologically composed of two components, namely carcinoma and sarcoma ones, with clear borderline or blend mutually. The proportion of cancer component in the whole tumor ranged from 5%-90%. The proportion of carcinoma was more than 50% in 76% of the cases, and less than 50% in 24% of cases, including 2 cases with<10% of carcinoma. In the cases of primary uterine MMMT, the main carcinoma type was high grade endometrioid carcinoma (55%, 16/29). In ovarian MMMT, the main carcinoma type was serous carcinoma (12/16), while that of cervical MMMT was squamous cell carcinoma. The others were clear cell carcinoma or the undifferentiated carcinoma. There was one carcinoma type in most cases, only 7 cases had two carcinoma types. Homologous sarcomas, including stromal sarcoma, leiomyosarcoma and high-grade spindle cell sarcomas, were more commonly found in uterine MMMT (72.4%, 21/29). While heterogenic sarcomas, including chondrosarcoma, osteosarcoma and rhabdomyosarcoma, were more commonly noted in ovarian MMMT (12/16) than MMMT of other sites. There were 10 cases that consisted of two types of sarcomas. The synchronous MMMT of uterus and ovary had similar morphology and the types of carcinoma and sarcoma. The tumor cells that spread or metastasized to lymph node, omentum, intestinal wall or skin were all carcinoma cells, and were morphologically consistent with the original tumors. Immunohistochemically, ER and PR were both negative (23/25 in uterine, 8/10 in ovarian tumors). p16 was strongly positive (11/11 in uterine tumors, and 6/6 in ovarian tumors), with similar expression patterns in the carcinoma and sarcoma components. p53 showed mutant-type staining (64%, 21/33) and expressed synchronously in carcinoma and sarcoma components. p53 mutation was found in 35% cases of endometrial carcinoma and 46.7% cases of non-endometrial carcinoma. p53 mutation was also found in only 31.8% cases of heterogenic sarcomas, but in 50% of non-heterogenic sarcomas. Twenty-eight cases (28/33, 85%) presented intact mismatch repair proteins, while 5 cases (5/33, 15%) presented deficient mismatch repair proteins.Conclusions:MMMT in female reproductive system is a rare high-grade biphasic tumor with complex and diverse morphology. The immunohistochemical features are characterized by negative ER/PR and strongly positive p16, mostly mutant p53 and proficient mismatch repair proteins. The patients with a high FIGO stage have worse prognosis.