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Multifocal fibrosing thyroiditis (MFT) is an enigmatic entity, characterized by multiple fibrotic scar-like lesions with a paucicellular fibrotic center surrounded by a cellular peripheral area with reactive-appearing follicular cell atypia and variable chronic inflammation. Although poorly recognized and likely underreported in surgical pathology, the entity is considered rare with only 65 cases to date–including the current one reported to expand on the preoperative findings of this under-recognized entity. The average age of the patients is 46.8 years (range 15–71 years), 94% are female, with female to male ratio of 15:1. Individual MFT lesions typically have a superficial location. The average number of fibrotic lesions is 15.4 (range 2–51 per MFT case). Their average size is 3.1 mm (range 0.4–15.1). MFT is a disorder of diseased thyroids, typically found postoperatively in glands removed for other reasons, such as chronic lymphocytic/Hashimoto thyroiditis (32.3%), follicular nodular disease (nodular hyperplasia) (30.1%), hyperthyroidism/diffuse hyperplasia (Graves disease) (9.2%). Intriguing is the association with papillary thyroid carcinoma–present in 38.5% of MFT cases, and particularly with sub-centimetric and multifocal papillary thyroid carcinoma, with which MFT can be confused. Cases where MFT is the only thyroid pathology (7.7%) can be preoperatively mistaken for papillary thyroid carcinoma, due to worrisome ultrasound (US) and cytologic features, both of which are here documented for the first time as a component of this article. Wider recognition of MFT and of its cytologic and ultrasound features at preoperative evaluation may reduce unnecessary thyroidectomies.

Background: The diagnosis of nodal nevi (NN) is challenging as they mimic melanoma metastases (MM), with a detection rate mostly ranging between 1% and 11% in sentinel lymph node biopsy (SLNB). Herein, we assessed the incidence of NN and the association with the clinical-pathological features of primary melanoma, adopting the updated European Organisation for Research and Treatment of Cancer (EORTC) protocol for SLNB. Methods: All cases of paired melanoma and SLNB were retrospectively evaluated (April 2019-May 2020). Appropriate statistical tests were adopted, with significant variables included in the logistic regression model. Results: 81 patients and a total of 186 lymph nodes (LNs) were included. Eleven patients had only NN and 4 had both NN and MM (18.5%); 29 LNs (15.6%) showed at least one NN and 12 (6.5%) showed more than one NN (a total amount of 43 NN was detected). All NN and none MM stained for p16. NN were associated with age < 60 years (p: 0.042), no ulceration (p: 0.025) and nevus-associated melanoma (NAM) (p: 0.018), with this latter being the only predictor at the logistic regression model (p: 0.022). Conclusions: The updated EORTC protocol shows a high number of NN and highlights a strong association with NAM.

Introduction: Serrated lesions are a heterogeneous group of lesions routinely evaluated with different morphologic subtypes, and colorectal carcinogenesis has been related to the understanding of the serrated pathway in these lesions. In this setting, BRAF V600E mutation has been demonstrated as a marker for the serrated carcinogenic evolution, while the mismatch repair protein (MMR) was recognized in a small subset of hyperplastic polyps. Design: This study aimed to evaluate the interobserver agreement among 6 pathologists in the morphological diagnosis of the serrated lesion according to WHO Classification; furthermore, the additional MMR (MLH1, PMS2, MSH2, MSH6) and BRAF V600E (VE1) mutation status were studied by immunohistochemistry and NGS analysis. Results: We evaluated 52 serrated lesions of the colon retrieved from our pathology archives in 2019. The cohort included 48 patients: 21 males and 27 females, with a mean age of 67 years (range 50-89), of which 77.1% were identified according to regional screening protocol. All hematoxylin and eosin slides were independently reviewed by each pathologist, who classified all samples according to the WHO Classification of Digestive System Tumor (Fleiss Kappa: 0.75). The immunohistochemical expression of MMR and BRAF was evaluated in 42 samples. Loss of MLH1 and PMS2 was recorded in one serrated sessile lesion (LSS) with dysplasia, but NGS analysis resulted negative. In contrast, BRAF V600E IHC resulted positive in 22 samples (52.4%), specifically in 5 hyperplastic polyps (71.4%), 10 LSS (66.6%), 5 LSS with dysplasia (45.5%) and 2 adenomatous polyps (100%), 1 TSA negative. All BRAF V600E IHC positive cases were confirmed by NGS analysis. Conclusion: To conclude, the interobserver agreement for morphological classification of serrated lesions resulted substantial; however, behind the morphological appearance, BRAF V600E resulted in predominant mutation in LSS and hyperplastic polyps, these observations confirmed the possibility to improve the classification with IHC BRAF V600E; especially for hyperplastic polyps, it may be crucial to identify precancerous lesions and different clinical management. Citation Format: Francesca Ambrosi, Costantino Ricci, Federico Chiarucci, Stefano Chilotti, Doriana Donatella Di Nanni, Angelo Gianluca Corradini, Maria Antonietta Cumiento, Dario De Biase, Michelangelo Fiorentino. What9s more in serrated lesions: interobserver agreement and molecular features [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2603.

Spinal intradural hemorrhage is a rare event; the most common causes of spinal bleeding are traumas, medical therapy with anticoagulants and thrombolytics, vascular malformations, and congenital defects of coagulation. Rarely, spinal cord tumors may cause hemorrhage. Herein, we report the case of a patient with acute and quickly worsening lumbar pain: the neurological examination revealed a flaccid paraplegia caused by an intradural lesion extending on the right side of the spinal cord from T1 to L2 vertebral level. Pathological examination revealed an hemorrhagic schwannoma. Acute spinal subdural hemorrhage caused by spinal schwannomas is a very rare occurrence (29 cases only have been previously reported). Review of the literature with clinico-diagnostic features is presented, surgical treatment is explained, and pathological findings with possible etiopathogenesis of hemorrhage are described.

Ovarian carcinomas represent a heterogeneous group of neoplasms consisting of separate entities with distinct risk factors, precursor lesions, pathogenesis, patterns of spread, molecular profiles, clinical course, response to chemotherapy, and outcomes. The histologic subtype and the related molecular features are essential for individualized clinical decision-making. The fifth edition of the World Health Organization classification of tumors of the female genital tract divides ovarian carcinomas into at least five main and distinct types of ovarian carcinomas: high-grade serous carcinoma, low-grade serous carcinoma, endometrioid carcinoma, clear cell carcinoma, and mucinous carcinoma. Molecular pathology has improved the knowledge of genomic landscape of ovarian carcinomas identifying peculiar alterations for every histologic subtype. It is well-known that high-grade and low-grade serous carcinomas are separate entities with entirely different morphologic and molecular characteristics. TP53 and BRCA mutations are typical of high-grade serous carcinoma, whereas BRAF and KRAS mutations frequently occur in low-grade serous carcinoma. Endometrioid and clear cell carcinomas are frequently associated with endometriosis. Endometrioid tumors are characterized by β-catenin alterations, microsatellite instability, and PTEN and POLE mutations, while ARID1A mutations occur in both endometrioid and clear cell carcinomas. Mucinous carcinomas are uncommon tumors associated with copy-number loss of CDKN2A and KRAS alterations and metastasis from other sites should always be considered in the differential diagnosis.

The presence of melanin pigment and melanocytic markers expression have been rarely reported in salivary gland tumors. Herein, two cases of carcinoma arising in pleomorphic adenoma of the parotid gland and showing diffuse expression of myoepithelial and melanocytic markers are described. The clinical-pathological clues useful in the differential diagnosis with melanoma are discussed. In addition, a review of the pertinent literature is also proposed, discussing the pathologic mechanisms potentially involved in this phenomenon. Supplementary Information The online version of this article (10.1007/s12105-021-01299-4) contains supplementary material, which is available to authorized users.