Mahmoud A. Khalifa

Angiomatoid fibrous histiocytoma (AFH) is a rare low-grade soft tissue neoplasm which typically occurs in the deep dermis or subcutis of extremities in children and young adults. We present a case of an 8-year-old boy who presented with progressive exertional dyspnea and fatigue, and was found to have a 4 cm right atrial mass. Surgical resection was performed and histology showed neoplastic cells with pseudoangiomatous spaces and mixed lymphocyte predominant chronic inflammation. Fluorescence in situ hybridization (FISH) demonstrated EWSR1 gene rearrangement and subsequent Next Generation Sequencing (NGS) identified a EWSR1::ATF1 fusion consistent with AFH. To our knowledge, this is a previously undescribed location for AFH and highlights the importance of keeping it under diagnostic consideration even in highly unusual sites.

Claudin-18 isoform 2 (CLDN18.2) is a tight junction protein that may become exposed on the tumor cell surface with loss of epithelial polarity, enabling therapeutic targeting. Although CLDN18.2-directed therapies have demonstrated efficacy in gastric and gastroesophageal adenocarcinoma, its expression in lower rectal adenocarcinomas remains poorly defined.Following institutional review board approval (STUDY00025960), we retrospectively evaluated primary rectal adenocarcinomas arising within 2 cm of the dentate line. CLDN18.2 immunohistochemistry was performed, with positivity defined as any tumor cell staining. Clinicopathologic features and outcomes were compared.Among 37 cases, 6 (16.2%) were CLDN18.2-positive. Most clinicopathologic variables were similar between groups. However, CLDN18.2-positive tumors were located significantly closer to the dentate line than CLDN18.2-negative tumors (mean 0.12 cm vs 0.59 cm; p=0.01). CLDN18.2-positive cases also showed higher observed recurrence (83.3% vs 29.0%; p=0.02) and shorter recurrence-free survival on univariate analysis, without a significant difference in overall survival.CLDN18.2 expression is present in a subset of lower rectal adenocarcinomas, particularly in tumors arising near the anorectal junction. These findings suggest possible anatomic and biologic heterogeneity in this setting. While an association with recurrence was observed, this should be interpreted cautiously given the small cohort size. Nevertheless, the identification of CLDN18.2 expression in this subset raises the possibility of biologic relevance with potential implications for future therapeutic stratification.

Endometriosis is defined by the presence of endometrial glands and stroma outside the uterine cavity. Although it typically presents within the pelvis, extragenital manifestations are well documented with gastrointestinal (GI) involvement being the most frequently affected organ system. We performed a retrospective study of histologically confirmed cases of endometriosis diagnosed at a single healthcare system between 2017 and 2024 to characterize the clinicopathologic features, anatomic distribution, and institutional frequency of GI tract involvement. A total of 1,964 cases of endometriosis were identified, of which 150 (7.7%) demonstrated GI tract involvement, which comprised our main cohort. The majority of patients had no documented prior history of endometriosis (97%). CT/MRI was the most common modality used for diagnosis with 51%. Non-specific abdominal or pelvic pain (53%) followed by uterine bleeding (23%) were the most common presenting symptoms. GI-specific involvement was found in only 17% of cases. Appendix was the most frequently involved site (77 cases) followed by rectum (45 cases), and sigmoid colon (40 cases). Involvement of a single isolated organ was seen in 56% of cases, with multi-site disease found in 44% of patients, and concurrent gynecological organ involvement found in 39% of cases. In 88% of cases, regular hematoxylin and eosin was used to render the diagnosis without the use of immunonohistochemistry (IHC). The heterogeneity in both clinical presentation and pathologic findings for gastrointestinal endometriosis highlights the diagnostic complexity, and emphasizes the need for increased awareness to avoid histologic misinterpretation and facilitate timely recognition and management of patients.

Background: Goblet cell adenocarcinoma (GCA) is a rare appendiceal neoplasm that may exhibit minimal cytologic atypia, rendering diagnosis highly dependent on architectural features. During routine practice, we observed a reproducible resection margin alteration that closely mimicked low-grade GCA.Methods: We retrospectively reviewed 33 consecutive appendectomy specimens (April 2024–August 2025) to characterize this finding and assess associated clinicopathologic variables.Results: A goblet cell–like resection margin artifact was identified in 12 cases (36%). The altered areas consisted of optically clear vacuolated profiles arranged in linear arrays or small clusters within the appendiceal wall, typically adjacent to thermal injury. Immunohistochemical studies in an index case were negative for epithelial and neuroendocrine markers, supporting a non-neoplastic process. The finding was strongly associated with endoloop ligation with energy-assisted transection (12/12, 100%), whereas stapler-only transection was observed exclusively in non-artifact cases (p = 0.004). Thermal injury (p < 0.001), mucin depletion (p = 0.009), marked wall edema (p < 0.001), and receipt of an open proximal margin (p = 0.025) were also significantly associated. Follow-up demonstrated no adverse clinical outcomes.Conclusions: This study describes a reproducible, procedure-related resection margin artifact that can closely mimic GCA. Recognition of this morphologic pattern and correlation with operative technique are essential to avoid overdiagnosis.

A: Comparison of serum estradiol levels vs BMI at baseline (pre-treatment) (p = 0.001). B: Serum estradiol vs BMI at surgery (post-treatment) (p = 0.0004) C: Change in serum estradiol vs BMI (p = 0.86)

Change in Ki-67 compared to change in steroid receptors

Comparison of clinicopathologic factors between participants who responded to exemestane (Ki-67 decrease) and did not respond to exemestane (Ki-67 increase)

Change in Ki-67 vs baseline steroid receptors

Changes in histologic diagnosis between baseline (pre-treatment) and surgery (post-treatment)

Comparison of change in Ki-67 with baseline (pre-treatment) serum estradiol level, p = 0.11