Rate of non-invasive follicular thyroid neoplasms with papillary-like nuclear features depends on pathologist's criteria: a multicentre retrospective Southern European study with prolonged follow-up.

PURPOSE: To determine the rate of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in a multi-institutional series from the Iberian Peninsula and describing this NIFTP cohort. METHODS: Retrospective study of papillary thyroid carcinoma (PTC) or well-differentiated tumours of uncertain malignant potential (WDT-UMP) diagnosed between 2005 and 2015 and measuring ≥5 mm in adult patients from 17 hospitals. Pathological reports were reviewed to determine the cases that fulfil the original criteria of NIFTP and histology was reassessed. Rates were correlated with the number of PTC and its follicular variant (FVPTC) of each institution. Demographic data, histology, management, and follow-up of the reclassified NIFTP cohort were recorded. RESULTS: A total of 182 cases with NIFTP criteria were identified: 174/3372 PTC (rate: 5.2%; range: 0-12.1%) and 8/19 WDT-UMP (42.1%). NIFTP rate showed linear correlation with total PTC (p: 0.03) and FVPTC (p: 0.007) identified at each centre. Ultrasound findings were non-suspicious in 60.1%. Fine-needle cytology or core biopsy diagnoses were undetermined in 49.7%. Most patients were treated with total thyroidectomy. No case had nodal disease. Among patients with total thyroidectomy, 89.7% had an excellent response evaluated 1 year after surgery. There were no structural persistence or relapses. Five patients showed residual thyroglobulin after 90 months of mean follow-up. CONCLUSIONS: NIFTP rate is low but highly variable in neighbouring institutions of the Iberian Peninsula. This study suggests pathologist's interpretation of nuclear alterations as the main cause of these differences. Patients disclosed an excellent outcome, even without using the strictest criteria.

A comprehensive diagnosis of a desmoplastic small round cell tumor of unusual location based on fine-needle aspiration cytology: Report of a case arising in the parotid gland and review of the literature.

Desmoplastic small round cell tumor (DSRCT) is rare and a highly aggressive neoplasm that typically involves the soft tissues of the abdomen or pelvis in children or young adults, showing a male predilection. Although it can occurs over a wide age range, the peak incidence is in the third decade of life. DSRCT usually shows widespread abdominal serosal involvement, and overall patient survival is poor. On the other hand, extra-abdominal DSRCT is very rare. DSRCT in major salivary glands has been reported, but it is extremely rare. In the majority of reported series diagnosis is made by the histological analysis of FFPE tissues together with immunohistochemistry (IHC) and molecular analysis, particularly the demonstration of chromosomal translocation involving EWSR1. Very few cases have been diagnosed so far by Fine Needle Aspiration (FNA) cytology. Moreover ancillary studies have been performed in all reported cases in FFPE samples. There is still controversy and lack of consensus regarding the suitability of cytological samples especially smears for immunocytochemical (ICC) and fluorescence in situ hybridization (FISH), what makes its standardization difficult. We report a case of a primary DSRCT of parotid gland in a 17-year-old male diagnosed by FNA cytology. The cytomorphological diagnosis was coupled with ICC and FISH analysis performed on stained smears. We emphasize the feasibility and reliability of cytological smears for the application of immunocytochemical and molecular techniques.