American Journal of Dermatopathology最新文献

Abstract: Solar elastotic bands (Raimer's bands) represent a rare clinical variant of severe solar elastosis that often affects forearms. Solar elastotic bands and keratoelastoidosis marginalis are associated with extensive chronic sun exposure (actinic damage). Repetitive trauma is also suspected of playing a causative role. We present a case of solar elastotic band of the forearm in which cytokeratin AE1/AE3 stains reveal positive staining in the dermis. This finding supports the hypothesis that trauma plays a role. We explore and review the histologic and clinical findings of several forms of solar elastosis, suggesting that these entities share many features in common.

Abstract: Synovial sarcoma is a malignant soft tissue neoplasm that can closely mimic carcinoma by histology and immunohistochemistry, making accurate diagnosis challenging in small or superficial biopsies. In this study, we report a rare case of a superficial biphasic synovial sarcoma with striking neuroendocrine differentiation, a biopsy of which was initially interpreted as a poorly differentiated carcinoma due to diffuse cytokeratin and neuroendocrine marker expression. Resection subsequently revealed a biphasic morphology, and molecular testing confirmed the presence of an SS18::SSX fusion, confirming the diagnosis of synovial sarcoma. This case highlights a potential diagnostic pitfall in dermatopathology and stresses the importance of confirmatory molecular testing in cases where both sarcoma and carcinoma are included in the differential diagnosis.

Abstract: Primary Cutaneous Ewing Sarcoma (PCES) is exceptionally rare and represent a notorious diagnostic mimicker of Merkel cell carcinoma (MCC), particularly when it aberrantly expresses neuroendocrine markers. This pitfall can lead to significant diagnostic error and inappropriate management. A 73-year-old woman presented with a progressive, FDG-avid nodule on the left upper arm. An initial punch biopsy revealed a malignant small round cell tumor with a classic neuroendocrine immunophenotype, including dot-like positivity for CK20 and Neurofilament, which did not allow distinction between PCES and MCC. Subsequently, wide local excision was performed. Histological and extensive immunohistochemical analyses were conducted on the excision specimen, and fluorescence in situ hybridization (FISH) was employed for molecular confirmation. Examination of the resectate showed a multinodular dermal tumor composed of uniform round cells. Immunohistochemistry revealed diffuse positivity for CD99 and NKX2.2, whereas S100 and SOX10 were negative. Crucially, FISH analysis confirmed an EWSR1::FLI1 gene fusion. The sentinel lymph node was negative for metastasis. This case exemplifies a profound diagnostic pitfall in which PCES closely mimicked the immunoprofile of MCC. It underscores that dot-like CK20 and Neurofilament staining are not entirely pathognomonic for MCC diagnosis. In the differential diagnosis of cutaneous round cell tumors, which includes metastases, melanoma, and several sarcoma types, the present case reveals the diagnostic challenges of cutaneous sarcomas and highlights the necessity of a multimodal approach for accurate diagnosis.

Abstract: Periungual Bowen disease is an uncommon form of squamous cell carcinoma in situ that may mimic benign pigmented lesions, such as melanocytic nevi. We report a case of a 36-year-old man who presented with an irregularly shaped brown macule on the periungual area of the right third finger, with a history of gradual enlargement over 8 years. The patient reported occasional periungual trauma because of nail picking but had no significant medical history. A punch biopsy was performed, and histopathological examination confirmed the diagnosis of Bowen disease. The lesion was completely excised, and no recurrence was observed during follow-up. This case highlights the importance of clinical suspicion and histological evaluation for chronic pigmented periungual lesions that may resemble benign conditions.

Abstract: Fibroepithelioma of Pinkus (FEP) is an uncommon histologic variant of basal cell carcinoma that classically arises on the trunk and proximal extremities. We present the case of a 59-year-old Hispanic man with a 15-year history of a slowly enlarging, intermittently painful nodule on the left plantar foot. Clinical examination revealed a pearly, telangiectatic, hyperkeratotic nodule, and biopsy demonstrated anastomosing cords of basaloid cells within a fibromyxoid stroma, consistent with FEP. This case highlights an atypical acral presentation of FEP and contributes to the limited literature documenting its occurrence on the plantar foot. Recognition of this rare variant in unusual anatomic locations is important, because persistent acral lesions may seem clinically benign yet require timely biopsy to ensure accurate diagnosis and appropriate surgical management.

Abstract: Cutaneous adnexal tumors are a heterogeneous group of neoplasms with diverse histopathologic features. Clear cell hidradenoma (CCH) and cutaneous mixed tumors are benign adnexal neoplasms that may share overlapping morphologic characteristics, making diagnosis challenging, particularly at uncommon acral sites. We report the case of a 60-year-old man who presented with a long-standing nodule on the hand. Histopathologic evaluation suggested a possible diagnosis of clear cell hidradenoma. There were also myxoid areas and a focal chondroid area as well, which are features seen in cutaneous mixed tumors. To further clarify the diagnosis, next-generation sequencing identified an in-frame TRPS1-PLAG1 gene fusion, confirming a diagnosis of cutaneous mixed tumor with phenotypic features of clear cell hidradenoma. This case highlights the diagnostic complexity of acral adnexal tumors with overlapping morphologic features. Molecular testing, such as next-generation sequencing, can be an essential adjunct in distinguishing between morphologically similar adnexal neoplasms, thereby guiding accurate diagnosis and management.

Abstract: Sweat gland (SG) neoplasms encompass a wide variety of benign or malignant adnexal skin tumors differentiating into the various segments of SG. Their diagnosis and classification are often difficult, and have relied mainly on histologic and immunohistochemical criteria. Several genomic alterations have been more recently discovered in SG tumors, and have been used as additional diagnostic criteria. Among them, fusions of the MYBL1 or the MYB gene (namely MYB::NFIB or MYBL1::NFIB) have been detected in a significant proportion of cutaneous and extracutaneous (breast and salivary gland) adenoid cystic carcinomas (AdCC), and have been regarded specific of this tumor type. We report here an exceedingly rare case of a benign neoplasm diagnosed as benign tubular SG adenoma that was unexpectedly found to harbor a MYBL1::NFIB fusion gene. This case expands the spectrum of SG tumors driven by fusions of MYBL1, and challenges the specificity of MYBL1 fusions for cutaneous AdCC.