Abstract:Primary cutaneous anaplastic large cell lymphoma (pcALCL) is an indolent CD30+ T-cell lymphoma, typically of T-cell receptor (TCR)-αβ origin...

earranged in non-Spitz melanomas (ie, bona fide melanomas without Spitz-nevus-like cytomorphology), with a reported frequency of less than 1%. As a result, the clinicopathologic features and prognosti...

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Melanoma arising in blue nevus (MBN) is a rare melanoma subtype with distinct molecular characteristics and biological behaviors compared to other cutaneous melanomas. However, limited data exists on ...

B-Raf Proto-Oncogene ( BRAF ) fusions are rare in melanomas. We present a case of cutaneous melanoma with a Ring Finger Protein 11 ( RNF11 ) ::BRAF fusion in a 63-year-old man with a history of stage IB melanoma on the right upper back (pT2apN0cM0; nonulcerated with a Breslow thickness of 1.2 mm). D …

Detection of Merkel cell carcinoma (MCC) micrometastases in sentinel lymph nodes (SLNs) often necessitates immunohistochemical studies like pancytokeratin (panCK) or CK20. However, panCK can label non-epithelial cells, particularly dendritic reticulum cells, complicating interpretation, while CK20 i …

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare primary cutaneous T-cell lymphoma with adipotropism characterized by infiltration of CD8 + T cells exhibiting a cytotoxic and αβ phenotype. Although SPTCL is typically indolent, distinguishing it from more aggressive cutaneous lymphoma …

Spitz tumors are a heterogeneous group of melanocytic neoplasms ranging from benign Spitz nevi to malignant Spitz melanomas, with atypical Spitz tumors/Spitz melanocytoma occupying an intermediate position within this biological spectrum. A hallmark of all these lesions is the presence of specific g …

Merkel cell carcinomas (MCCs) exhibit diverse molecular profiles, often categorized by their association with Merkel cell polyoma virus (MCPyV). MCPyV-associated MCCs typically display a low tumor mutational burden (TMB), lacking both somatic mutations and ultraviolet signature. By contrast, MCPyV-n …

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Anaplastic lymphoma kinase (ALK)-positive histiocytosis was described in 2008 as a rare histiocytic proliferation in early infancy, accompanied by hepatosplenomegaly and hematological abnormalities.1 ...

Diffuse cutaneous ALK-immunoreactive histiocytosis with MEF2C::FLT3 fusion

Over the past 4 years, trichorhinophalangeal syndrome type 1 (TRPS1) has rapidly gained attention among practicing pathologists, with numerous studies emerging that both support and question its diagnostic utility. Initially regarded as a highly specific marker for tumors of mammary origin, TRPS1 is …

Extramammary Paget disease (EMPD) predominantly manifests de novo as primary EMPD, with less than 30 % of cases associated with underlying internal malignancy (secondary EMPD). Differentiating primary from secondary EMPDs based solely on histopathology poses challenges, often necessitating supplemen …

TRPS1 may be useful to distinguish MPDs/EMPDs from MISs, but its utility is limited in distinguishing them from other pagetoid intraepidermal neoplasms such as SCCISs.