Oral Undifferentiated Pleomorphic Sarcoma: A Novel Gene Fusion and a Comprehensive Literature Review.

Undifferentiated pleomorphic sarcoma (UPS) is a rare, high-grade soft-tissue sarcoma characterized by a patternless proliferation of bizarre pleomorphic tumor cells lacking identifiable lineage differentiation. Its occurrence in the oral cavity is exceptionally uncommon and poses significant diagnostic challenges due to its morphological overlap with a wide spectrum of other malignancies. : We report a novel case of oral UPS in a 54-year-old woman, characterized by an exceptionally large size and a rapidly progressive clinical course.

Atypical Spitz Tumor/Spitz Melanocytoma Revealing a VIM::NTRK3 Gene Fusion: Clinicopathological Correlation of a Unique Molecular Finding.

Spitz tumors are a heterogeneous group of melanocytic neoplasms ranging from benign Spitz nevi to malignant Spitz melanomas, with atypical Spitz tumors/Spitz melanocytoma occupying an intermediate position within this biological spectrum. A hallmark of all these lesions is the presence of specific genetic alterations, distinct from those seen in common nevi, that include, among others, receptor tyrosine kinase fusions. NTRK3 gene rearrangements are rare, with only a few fusion partners described in the existing literature (ETV6, MYO5A, MYH9, and SQSTM1).

Artificial Intelligence in the Histopathological Assessment of Non-Neoplastic Skin Disorders: A Narrative Review with Future Perspectives.

Artificial intelligence (AI) is rapidly transforming diagnostic approaches in different fields of medical sciences, demonstrating an emerging potential to revolutionize dermatopathology due to its capacity to process large amounts of data in the shortest possible time, both for diagnosis and research purposes. Different AI models have been applied to neoplastic skin diseases, especially melanoma. However, to date, very few studies have investigated the role of AI in dermatoses.

Perineuriomatous Nevus: A New Case Presentation With a Brief Review of the Literature.

Perineuriomatous nevus (PN) is a rare variant of neurotized spindle-cell melanocytic nevus, first described in 2011, characterized by the expression of perineurioma markers such as epithelial membrane antigen and CD34 in a distinctive fingerprint-like pattern. Although PN is uncommon and not fully understood in terms of pathogenesis, recent studies have explored its definition, etiology, diagnosis, and differential diagnosis, particularly distinguishing it from benign and malignant entities such as neurocristic hamartoma and desmoplastic melanoma. Accurate diagnosis requires thorough morphologic and immunohistochemical analysis.

The Rarity in the Rarity: A Rare Case of Bednar Tumor (Pigmented Dermatofibrosarcoma Protuberans) Localized on Acral Skin With Negative COL1A1-PDGFB Fusion on Fluorescence In Situ Hybridization.

Dermatofibrosarcoma protuberans (DFSP) is a rare, low-grade fibroblastic tumor that typically exhibits CD34 positivity and a storiform growth pattern. Although commonly found on the trunk and proximal extremities, DFSP can also present in less frequent locations, such as the head, neck, and acral sites. This report discusses a rare case of pigmented DFSP, also known as Bednar tumor, located on the back of the left hand in a 48-year-old woman.

Clear Cell Sarcoma (CCS) of the Soft Tissue: An Update Narrative Review with Emphasis on the Utility of PRAME in Differential Diagnosis.

Clear Cell Sarcoma (CCS) of soft tissue is a rare and highly malignant neoplasm primarily affecting young adults, often presenting in the deep soft tissues of the extremities. Despite morphological and immunophenotypic similarities to melanoma, CCS arises from connective tissues and is characterized by a distinct genetic hallmark: the EWSR1-ATF1 fusion resulting from t(12;22)(q13;q12) translocation. This genetic signature is absent in melanoma, making molecular diagnosis essential for accurate differentiation.

Gene Fusion-Driven Cutaneous Adnexal Neoplasms: An Updated Review Emphasizing Molecular Characteristics.

Gene rearrangements or fusions have emerged as critical oncogenic drivers in various cutaneous adnexal neoplasms. This review offers a comprehensive overview of both established and recently identified molecular alterations, with a specific focus on gene fusions. Key alterations discussed include YAP1 rearrangements, CRTC1::MAML2 fusions, BRD3 rearrangements, MYB::NFIB fusions, ETV6::NTRK3 fusions, and PLAG1 rearrangements, alongside rarer fusion transcripts, such as MEF2C::SS18 , FOXK1::GRHL1/2 , GPS2::GRHL , and RARA::NPEPPS .

Squamomelanocytic Tumor, An Entity Still Shrouded in Mystery: Case Report and Literature Review.

Cutaneous squamomelanocytic tumor (SMT) is a very rare cutaneous malignancy, composed of a dual phenotypic population of both malignant melanocytes and keratinocytes, intimately intermingled together. Herein, we report a new case of a SMT occurring in an 82-year-old man, located on the scalp. Histopathology revealed a mixed population consisting of squamous cell carcinoma and melanoma within the same lesion, also confirmed using immunohistochemical staining for high molecular-weight cytokeratins (HMWCKs) and Melan-A.

Hidradenocarcinoma of the Chest With Axillary Lymph Node Metastasis: Report of 2 Cases and Systematic Literature Review of a Breast Cancer Mimicker.

Hidradenocarcinoma (HAC) is a rare malignant neoplasm originating from eccrine sweat glands, often presenting diagnostic challenges because of its resemblance to other malignancies, particularly breast cancer when occurring in the chest region. This report describes 2 cases of HAC with axillary lymph node metastasis, both initially misinterpreted clinically. The first case involved a 63-year-old woman with a sternal mass, near the right breast, initially suspected to be a sebaceous cyst.

LMNA::NTRK1 and PRDX1::NTRK1 Atypical Spitz Tumor: A Report of Two Additional Cases With Histological, Immunohistochemical, and Molecular Insights.

Over the past decade, advancements in molecular biology have contributed to changes in the diagnostic classification of Spitz neoplasms, including Spitz nevi, atypical Spitz tumors, and Spitz melanomas. The recent World Health Organization classification of skin tumors identifies fusion kinases, including NTRK1, NTRK2, and NTRK3, as critical drivers of these lesions. New fusion genes have continued to expand the spectrum of known molecular alterations, particularly within the category of Spitz NTRK-rearranged lesions.

The Rarity in the Rarity: Presentation of Two Rare and Unusual Cases of Nodular Fasciitis and Proliferative Fasciitis.

Nodular fasciitis (NF) and proliferative fasciitis (PF) are benign, reactive mesenchymal neoplasms that can mimic malignancies due to their rapid growth and histological characteristics. NF typically affects the subcutaneous tissue, occasionally involving muscles and fascia, predominantly in young adults, and appears frequently in the upper extremities, trunk, and head/neck. PF, a pseudosarcomatous lesion, primarily occurs in the subcutaneous tissue of adults aged 40-70 years and is uncommon in younger populations.

Mast cell density in Merkel cell carcinoma and its correlation with prognostic features and MCPyV status: a pilot study.

Merkel cell carcinoma (MCC) is a rare, highly aggressive, primitive neuroendocrine carcinoma of the skin, the origin of which is not yet fully understood. Numerous independent prognostic factors have been investigated in an attempt to understand which are the most important parameters to indicate in the histological diagnostic report of MCC. Of these, mast cells have only been studied in one paper before this one.

Kinase Fusions in Spitz Melanocytic Tumors: The Past, the Present, and the Future.

In recent years, particular interest has developed in molecular biology applied to the field of dermatopathology, with a focus on nevi of the Spitz spectrum. From 2014 onwards, an increasing number of papers have been published to classify, stratify, and correctly frame molecular alterations, including kinase fusions. In this paper, we try to synthesize the knowledge gained in this area so far.

Poorly Differentiated Cutaneous Squamous Cell Carcinoma (cSCC) or Lymphoepithelioma-like Carcinoma of the Skin (LELCS) with Squamous Pearls: A Case Presentation with Emphasis on Histomorphological Features and Classification Debates.

Lymphoepithelioma-like carcinoma of the skin (LELCS) is a rare primary skin cancer, with an annual incidence of 1/100,000 and about 85 cases published in the literature. It is considered the cutaneous counterpart of undifferentiated nasopharyngeal carcinoma (UNC, Schmincke-Regaud tumor) but has no association with EBV. We present an interesting case with features of LELCS in a 93-year-old man, right frontal-orbital region, diagnosed histologically and with immunohistochemical features.

Blastic Plasmocytoid Dendritic Cell Neoplasm (BPDCN): Clinical Features and Histopathology with a Therapeutic Overview.

Blastic Plasmacytoid Dendritic Cell Neoplasms (BPDCNs) are a rare, highly aggressive hematological malignant neoplasm that primarily involve the skin, bone marrow, lymph nodes and even extra-nodal sites. The rarity and relative poor description of cases in the literature make it necessary to review and further studies that deeply investigate this entity not only in a histopathological but also molecular field. In August-September 2023, we searched MEDLINE, PubMed and Scopus for randomized controlled trials (RCTs), narrative and systematic reviews, meta-analyses, observational studies (either longitudinal or retrospective), and case series published in English in the last 25 years using the keywords BPDCN, PDCs, Blastic NK-cell lymphoma, agranular CD4+ NK leukemia/lymphoma, agranular CD4+ CD56+ hematodermic neoplasm/tumor.

Endocrine Mucin-Producing Sweat Gland Carcinoma: Case Presentation with a Comprehensive Review of the Literature.

(1) Background: Endocrine Mucin-Producing Sweat Gland Carcinoma (EMPSGC) is a rare, low-grade, neuroendocrine-differentiated, cutaneous adnexal tumor, officially recognized by the World Health Organization (WHO) Skin Tumors Classification in 2018 as a separate entity and homologue of endocrine ductal carcinoma in situ (eDCIS)/solid papillary carcinoma of the breast. Although it is more frequent in the female sex, between 60 and 70 years old, in the peri-orbital region, EMPSGC has also been described in the male sex, in subjects under 60 and over 80, and in extra-eyelid localizations (cheek, temple, scalp), but also in extra-facial localizations (chest and scrotum). (2) Methods: We present the clinical case of a 71-year-old woman with an undated lesion of the scalp, which presented as a nodule, skin-colored, and 2.

Artificial Intelligence Applied to a First Screening of Naevoid Melanoma: A New Use of Fast Random Forest Algorithm in Dermatopathology.

Malignant melanoma (MM) is the "great mime" of dermatopathology, and it can present such rare variants that even the most experienced pathologist might miss or misdiagnose them. Naevoid melanoma (NM), which accounts for about 1% of all MM cases, is a constant challenge, and when it is not diagnosed in a timely manner, it can even lead to death. In recent years, artificial intelligence has revolutionised much of what has been achieved in the biomedical field, and what once seemed distant is now almost incorporated into the diagnostic therapeutic flow chart.

Immunohistochemical Expression of Programmed Cell Death Ligand 1 (PD-L1) in Human Cutaneous Malignant Melanoma: A Narrative Review with Historical Perspectives.

Programmed death-ligand 1 (PD-L1) is the primary ligand of the receptor programmed death-1 (PD-1) which is constitutively expressed or activated in myeloid, lymphoid (T, B and NK), normal epithelial cells, and cancer. The PD-1/PD-L1 interaction is crucial for the physiological development of immunological tolerance but also in the development of the cancer. Among these, malignant melanoma represents a tumour in which the immunohistochemical expression of PD-L1 is important to guide future therapeutic choices based on the presence/absence of expression.

Giant Soft Tissue Leiomyosarcoma of the Left Lower Extremity: Case Presentation With a Review of the Literature.

Leiomyosarcoma (LMS) accounts for approximately 5-10% of soft tissue sarcomas, with an estimated incidence in the United States (US) of less than one case/200,000 persons, more frequent in women than men. Approximately two-thirds of LMSs are retroperitoneal, abdominal, and mediastinal. Localized, soft tissue LMSs represent a lower percentage, with the lower limbs and trunk being the most frequently involved sites.

Cutaneous Sarcoidosis-like Eruption Following Second Dose of Moderna mRNA-1273 Vaccine: Case or Relationship?

Various adverse reactions to SARS-CoV-2 vaccines have been described since the first months of the vaccination campaign. In addition to more frequent reactions, rare reactions, such as sarcoidosis-like, rashes have been reported. We present a case of a 23-year-old woman with a rash on the chin and peribuccal region, which developed approximately 3 weeks after the administration of the second dose of the Moderna mRNA-1273 vaccine.

T Cell Immunoglobulin and Mucin Domain 3 (TIM-3) in Cutaneous Melanoma: A Narrative Review.

T cell immunoglobulin and mucin domain 3 (TIM-3) is an inhibitory immunocheckpoint that belongs to the TIM gene family. Monney et al. first discovered it about 20 years ago and linked it to some autoimmune diseases; subsequent studies have revealed that some tumours, including melanoma, have the capacity to produce inhibitory ligands that bind to these receptor checkpoints on tumour-specific immune cells.

Is It Time to Supersede the Diagnostic Term "Melanoma In Situ with Regression?" A Narrative Review.

Traditionally, the term melanoma in situ (MIS) is used to designate a horizontal (radial) growth phase of malignant melanoma (MM) in which there is no histological evidence of any invasion (or microinvasion) of neoplastic melanocytic cells into the superficial or papillary dermis. In daily dermatopathological practice, we are faced with misleading definitions, such as "melanoma in situ with regression," which risk affecting homogeneity for comparison purposes of pathological reports of malignant melanoma. The authors conducted a literature review using PubMed and Web of Science (WoS) as the main databases and using the following keywords: "Malignant Melanoma in situ" or "Melanoma in situ" and "regression" and/or "radial growth phase regression.