Journal of Cutaneous Pathology最新文献

Primary cutaneous apocrine carcinoma (PCAC) is an exceptionally rare cutaneous malignancy originating from apocrine glands, occurring most commonly in the axilla and anogenital regions. It typically follows a slow-growing clinical course, although aggressive behavior has been documented in select cases. While local recurrence and regional metastasis are not uncommon in PCAC, instances of distant metastases are rare, with only a handful of cases reported, including involvement of the liver, bone, and lung. We present a unique case of PCAC with pagetoid features arising in the groin and metastasizing to the esophagus, a highly unusual presentation not well described in the existing literature. PCAC manifesting as extramammary Paget's disease (EMPD), characterized by single malignant epithelial cells scattered throughout the epidermis, represents a rare and diagnostically challenging variant. Its ability to mimic metastatic carcinomas from various organs necessitates thorough clinical and pathological correlation for accurate diagnosis. This case report aims to illuminate the potentially aggressive behavior of PCAC and emphasizes the need for long-term surveillance and awareness of its less typical presentations.

Eccrine spiradenomas are benign sweat gland neoplasms that rarely undergo malignant transformation. Carcinosarcoma arising from an eccrine spiradenoma is exceptionally rare. A 41-year-old male presented with a rapidly growing neck/shoulder mass, progressive numbness, spasticity, and weakness. Further workup additionally revealed an epidural mass with spinal cord compression. Both masses were excised and predominantly showed morphologic features of high-grade osteosarcoma, with overtly malignant spindled cells producing lace-like osteoid. However, a single section from the upper back mass contained a roughly 2 mm focus of conventional eccrine spiradenoma, with an adjacent small focus having features of a poorly differentiated non-small cell carcinoma. The final diagnosis was that of a high-grade carcinosarcoma with heterologous osteosarcomatous differentiation, arising from a pre-existing eccrine spiradenoma, with metastasis to the T4-5 epidural region. The patient experienced rapid regrowth of the spinal mass and underwent radiotherapy but had unresectable metastatic disease at 2 months follow-up. We describe what is to our knowledge only the 21st example of carcinosarcoma arising from eccrine spiradenoma, mimicking metastatic osteosarcoma. Awareness of this very rare entity, careful sampling, close microscopic examination, and, in selected cases, ancillary immunohistochemistry are the keys to making this challenging diagnosis.

FUS::TFCP2-rearranged rhabdomyosarcoma is a recently identified malignant neoplasm characterized by immunohistochemical evidence of the co-expression of rhabdomyoblastic markers and ALK. Herein, we report a case of cutaneous spindle cell/sclerosing rhabdomyosarcoma with FUS::TFCP2 fusion that was initially interpreted as an ALK-rearranged mesenchymal neoplasm in a 43-year-old male due to negative desmin expression, a rhabdomyoblastic marker. RNA sequencing was performed to detect ALK fusion counterparts; however, no ALK counterpart fusion was observed, and FUS::TFCP2 fusion was detected. Myogenin was negative, but MyoD1 was positive. Detection of FUS signals using FISH led to the diagnosis of FUS::TFCP2-rearranged rhabdomyosarcoma. In cases of ALK positivity and spindle cell or epithelioid cell morphology, FUS::TFCP2-rearranged rhabdomyosarcoma should be considered in the differential diagnosis using staining for rhabdomyoblastic markers other than desmin.

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.