Journal of Cutaneous Pathology最新文献

Cutaneous large cell neuroendocrine carcinoma (LCNEC) is a rare and poorly understood malignancy. Here we describe the clinicopathological characteristics of six cutaneous LCNEC case. A retrospective chart and slide review of PCLCNEC cases at a large commercial dermatopathology practice from January 2017 to May 2025 was performed. Patient characteristics, histopathologic features, and immunohistochemical profiles, including Merkel cell polyoma virus large T antigen/MCPyV antigenicity, were summarized. Demographically, PCLCNEC occurred in elderly white patients, presenting as a rapidly progressing nodule in sun-exposed skin. Histologically, the tumors were characterized by predominantly infiltrative growth patterns with varying levels of neuroendocrine architectural and cytologic features, including rosette and trabeculae formation, organoid nesting, and peripheral palisading. All were positive for CK7 and neuroendocrine markers and negative for MCPyV, CK20, and TTF1 expression by immunohistochemistry. Metastasis was identified in one patient, while the remaining five patients had no evidence of disease following wide local excision with a median follow-up period of 25 months. This series contributes valuable insights into the characterization and diagnosis of primary cutaneous LCNEC. In conjunction with previously reported data, we suggest that the morphology and immunophenotype support further inquiry into its potential distinction as a unique cutaneous entity.

Hidradenoma can exhibit several cell types, including clear cells, polyhedral eosinophilic cells, squamoid cells, mucinous cells, oxyphilic (oncocytic) cells, and transitional (intermediate) cells. However, sebocytes have not yet been described in hidradenoma. Here, we present a case of CRTC1::MAML2-positive hidradenoma with sebaceous differentiation. In addition, this tumor had two cell-type layers that were morphologically similar to apocrine glandular cells and myoepithelial cells throughout the lesion. A 66-year-old male presented with a 20 mm nodule on his upper lip with a 3-year history. Histopathological examination revealed a multinodular tumor adherent to the overlying epidermis. No surrounding salivary glands were seen. The tumor consisted of eosinophilic ductoglandular cells surrounded by basaloid cells at the outer periphery. Numerous sebocytes were scattered throughout the tumor. Severe nuclear atypia or mitotic figures were not observed. Immunohistochemical examination showed no expression of α-smooth muscle actin, calponin, and S100 protein in the tumor cells. Adipophilin highlighted scattered sebocytic tumor cells. Immunoexpression of MLH1, PMS2, MSH2, and MSH6 was preserved. MAML2 break-apart fluorescence in situ hybridization revealed frequent split signals. Sanger sequencing revealed a CRTC1(e1)::MAML2(e2) fusion. Based on this report, hidradenoma should be included in the differential diagnosis of cutaneous adnexal tumors with sebaceous differentiation other than sebaceous adnexal tumors. In addition, sebocytes should be added to the list of tumor cell types in hidradenoma.

The global demand for aesthetic procedures has been steadily increasing, driving the development of new techniques and materials to meet this need. However, these procedures are not without risks, including the formation of subcutaneous nodules following injectable treatments. Histopathology plays a crucial role in identifying skin fillers based on their distinct morphological characteristics. In this article, we present two cases of subcutaneous nodules associated with the application of Elleva poly-l-lactic acid, providing a detailed histopathological analysis.

We report a rare case of plasmablastic lymphoma (PBL) in an HIV-positive patient with nodal and gastric involvement, who also showed intravascular PBL cells within a longstanding Kaposi sarcoma (KS) skin lesion.

Acanthamoeba is a free-living ameba, known to most commonly cause amebic keratitis in contact lens users and granulomatous amebic encephalitis in immunocompromised patients. Cutaneous Acanthamoebiasis as a single-organ manifestation is less common. We report two cases seen in our department. Case one is a 23-year-old hospitalized patient with systemic lupus erythematosus and pancytopenia who acutely developed nodules on the extremities. Biopsy showed lymphohistiocytic inflammation and focal coagulative necrosis in the subcutaneous fat. Acanthamoeba trophozoites and cysts were apparent in H&E-stained sections and highlighted by PAS and GMS stains. PCR studies were positive for Acanthamoeba species. Case two is an 81-year-old with diffuse large B-cell lymphoma on idelalisib, who presented with a three-week history of ulcerating nodules on the extremities. Biopsy from the left arm exhibited a mixed deep dermal infiltrate with neutrophils and histiocytes while biopsy from the right arm exhibited granulomatous inflammation. Acanthamoeba trophozoites and cysts were apparent in H&E and PAS-stained sections, confirmed to be Acanthamoeba by PCR. Cutaneous Acanthamoebiasis should be considered in biopsies of cutaneous nodules from immunocompromised patients. The histopathologic inflammatory changes are variable and non-specific, while the organisms are easily overlooked due to their resemblance to histiocytes. Familiarity with these features is essential for accurate, timely diagnosis.