Pleomorphic (giant cell) carcinoma revisited: A historical perspective and conceptual reappraisal

[Undifferentiated and dedifferentiated renal cell carcinomas : Morphomolecular aspects and differential diagnosis in light of recent developments]

Histological subtyping of diverse renal cell carcinomas (RCCs) has seen significant changes during the last two decades. This resulted in the introduction of several new phenotypically and genetically defined entities, many which are also listed in the current WHO classification. Some of these well-defined entities may, under certain circumstances, undergo a process of dedifferentiation resulting in loss of their phenotypic and immunohistochemical features, hence adopting a non-descript anaplastic morphology. Accordingly, the original entity-defining tumor clone might be either totally overgrown and lost or just be missed by sampling the tumor. This final common pathway of dedifferentiation results in several oncological disadvantages and prevents a histology-tailored approach to systemic therapy. In addition, the possibility of inherited cancer as in the case of SDH- and FH-deficient RCC would be easily overlooked if the exact subtyping is not possible. This overview article illuminates the main RCC subtypes that may undergo dedifferentiation and their differential diagnostic approach.

Elusive and Aggressive: Unraveling SMARCB1/INI1-Deficient Undifferentiated Carcinoma With Rhabdoid Features Arising From the Colon: A Case Report and Comprehensive Literature Review

Undifferentiated carcinomas are highly aggressive tumors with a dismal prognosis. A subset of these tumors has been associated with inactivation or mutations of the Switch/Sucrose Nonfermenting (SWI/SNF) remodeling complex. Our understanding of the relationship between the clinicopathological features and molecular profiling of SWI/SNF-deficient undifferentiated carcinoma is still evolving due to its rarity. We herein present a rare tumor of undifferentiated carcinoma with SMARCB1/INI1 deficiency arising from the colon. The histology revealed a tumor composed of sheets of discohesive, high-grade epithelioid cells with rhabdoid morphology along with anaplastic giant cells. Additionally, there was a significant infiltration of inflammatory cells in the background. Immunohistochemical (IHC) analysis supported the diagnosis of carcinoma with loss of INI1 expression, the tumor was mismatch repair protein proficient. Molecular analysis demonstrated an oncogenic KRAS mutation (p.G12D), whereas it was wild-type BRAF, and wild-type NRAS. The diagnosis of SWI/SNF-deficient undifferentiated carcinoma can be challenging. Correlation with clinical findings, in conjunction with IHC work-up and molecular analysis, is of utmost importance to arrive at the appropriate diagnosis and exclude potential mimics.

Pleomorphic Giant Cell Carcinoma and Periurethral Abscess: A Case Report

Prostate cancer (PCa) is the most common solid malignancy in men in the UK. Pleomorphic giant cell carcinoma (PGCC) is a rare, aggressive variant of prostate adenocarcinoma. PGCC is associated with a poor prognosis and high Gleason-grade characteristics, often occurring in patients with a history of PCa treatment. This case report details the presentation of a 78-year-old male with a background of PCa, previously treated with radiotherapy and androgen deprivation therapy, who was initially diagnosed with a periurethral abscess. Despite initial treatment, the patient experienced recurrent symptoms, leading to further investigations and surgical intervention. Histopathological analysis of tissue samples revealed PGCC, highlighting the importance of considering this malignancy in cases of recurrent abscesses in patients with a history of PCa. This case underscores the necessity of early suspicion, prompt investigation, and multidisciplinary management in complex cases involving PGCC, emphasizing the need for heightened awareness of this rare pathology in clinical practice.

Beyond the WHO 2020 Classification of Female Genital Tumors: Types of Endometrial Cancer: A Pathological and Molecular Focus on Challenging Rare Variants

Endometrial carcinoma is a heterogeneous group of malignancies characterized by distinct histopathological features and genetic underpinnings. The 2020 WHO classification has provided a comprehensive framework for the categorization of endometrial carcinoma. However, it has not fully addressed the spectrum of uncommon entities that are currently not recognized by the 2020 WHO and have only been described in the form of small case series and case reports. These neoplasms represent a real diagnostic challenge for pathologists; furthermore, their therapeutic management still remains controversial and information regarding tumor prognosis is very limited. This review aims to elucidate these lesser-known variants of endometrial carcinoma. We discuss the challenges of identifying these rare subtypes and the molecular alterations associated with them. Furthermore, we propose the need for expanded classification systems that include these variants to enhance clinical outcomes and research efforts. We believe that a better histological typing characterization of these entities may lead to more reproducible and accurate diagnoses and more personalized treatments. By raising awareness of these rare entities, we also hope to encourage further investigation and integration into clinical practice to improve patient care in endometrial carcinoma.

Unusual or Uncommon Histology of Gastric Cancer

This review comprehensively examines the diverse spectrum of gastric cancers, focusing on unusual or uncommon histology that presents significant diagnostic and therapeutic challenges. While the predominant form, tubular adenocarcinoma, is well-characterized, this review focuses on lesser-known variants, including papillary adenocarcinoma, micropapillary carcinoma, adenosquamous carcinoma, squamous cell carcinoma (SCC), hepatoid adenocarcinoma, gastric choriocarcinoma, gastric carcinoma with lymphoid stroma, carcinosarcoma, gastroblastoma, parietal cell carcinoma, oncocytic adenocarcinoma, Paneth cell carcinoma, gastric adenocarcinoma of the fundic gland type, undifferentiated carcinoma, and extremely well-differentiated adenocarcinoma. Although these diseases have different nomenclatures characterized by distinct histopathological features, these phenotypes often overlap, making it difficult to draw clear boundaries. Furthermore, the number of cases was limited, and the unique histopathological nature and potential pathogenic mechanisms were not well defined. This review highlights the importance of understanding these rare variants for accurate diagnosis, effective treatment planning, and improving patient outcomes. This review emphasizes the need for ongoing research and case studies to enhance our knowledge of these uncommon forms of gastric cancer, which will ultimately contribute to more effective treatments and better prognostic assessments. This review aimed to broaden the pathological narrative by acknowledging and addressing the intricacies of all cancer types, regardless of their rarity, to advance patient care and improve prognosis.

Clinicopathological features and differential diagnosis of gastric pleomorphic giant cell carcinoma

The aim of this study was to investigate the clinicopathological features and differential diagnosis of gastric pleomorphic giant cell carcinoma. Histopathology, immunohistochemistry, and human epidermal growth factor receptor 2 (HER2) gene testing were conducted for seven cases of gastric pleomorphic giant cell carcinoma. In histomorphological terms, all seven cases involved pleomorphic giant cell carcinoma, accounting for more than 10% of the entire tumor, with pleomorphic spindle cells and giant cells mixed with various histomorphological structures of adenocarcinoma with high, intermediate, and low differentiation. There was large heterogeneity in the HER2 protein expression and HER2 gene amplification in the gastric pleomorphic giant cell carcinoma, and both levels of HER2 were focal in three cases, accounting for 42.9% (3/7). The mismatch repair gene proteins MLH1, MSH2, PMS2, and MSH6 were positive. Routine immunohistochemical markers, i.e., pan-cytokeratin, epithelial membrane antigen, villin, caudal-type homeobox 2, E-cadherin, and p53, were positive in the gastric pleomorphic giant cell carcinoma, while vimentin, calponin, smooth muscle actin, nestin, S-100, cluster of differentiation (CD) 99, desmin, and CD34 were focally expressed in both the spindle and the giant cells, with Ki-67-positive cells accounting for 70-80%. Gastric pleomorphic giant cell carcinoma presents multiple histomorphological features and is easily confused with various tumors. Clarifying the histopathological features of this type of tumor is important for differential diagnosis and precise treatment.

Endometrial giant cell carcinoma: new insights from a morphological, immunohistochemical, and molecular analysis of three cases

Herein, we present a morphological, immunohistochemical, and molecular analysis of three cases of endometrial giant cell carcinoma (EGCC) with a literature review. Patient age was 55 to 76 years. The tumors were limited to the uterus and showed dyshesive, bizarre giant cells with numerous atypical mitoses. Minor components were low-grade endometrioid, spindled/myxoid (case nos. 1 and 2), serous (case no. 3), and undifferentiated (all cases). The giant cells were e-cadherin-, cytokeratins/EMA + (focal/multifocal), hormone receptors + (focal/multifocal), vimentin + , p16 + (diffuse), CD68-, α-FP-, β-HCG-, muscle markers-, CD10-, and ERG-. Case no. 3 was p53-abnormal. All cases were mismatch repair-proficient and microsatellite-stable. No POLE mutations were detected. Based on our and previous reports, EGCC is often accompanied by a conventional carcinomatous component (mostly endometrioid) and shows partial loss epithelial markers and negativity for specific differentiation markers. EGCC shows evident similarities to both undifferentiated/dedifferentiated carcinoma and carcinosarcoma and should be managed similarly. Unlike the latter two, EGCC might preferentially derive from "no-specific-molecular-profile" carcinomas.