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Primary cutaneous gamma/delta T-cell lymphoma (PCγδTCL) is a rare form of cutaneous lymphoma characterized by abnormal clonal proliferation of mature, activated gamma-delta T cells expressing the γδ heterodimer of the T-cell receptor (TCR). As an entity, PCγδTCL has recently undergone diagnostic revision since its introduction in the 2008 WHO classification of cutaneous lymphomas and confirmedin 2016. Nonetheless, diagnosis remains difficult both clinically and histologically, given its broad range of clinical manifestations and immunohistochemical phenotypes. Herein, we present a rare case of CD8+ PCγδTCL with a discussion highlighting theheterogeneity within this entity.

Cutaneous leukocytoclastic vasculitis (LCV) is a disease thought to be related to the presence of immune complex deposition within small blood vessel walls. A 58-year-old female presented with purpuric papules on both legs, occurring concurrent with urinary symptoms. Histologically, an intraepidermal blister with luminal fragmented neutrophils was present. A dermal infiltrate was observed surrounding blood vessels; mild perivascular leukocytoclastic debris favored a diagnosis of LCV. Both direct immunofluorescence and immunohistochemistry staining also favored a diagnosis of LCV. Reactivity of the involved vessels was observed to multiple antibodies and complement, with overexpression of von Willebrand factor, CD15, and CD45. The ribosomal protein Phospho-S6 was also detected within the involved vessels, and on the blister roof and floor. The clinical triggering factor was a urinary infection that had progressed to urosepsis; the symptoms were effectively treated. We present an unusual case, where multiple immune reactions correlate with clinical and histologic changes characteristic of LCV. [ABSTRACT FROM AUTHOR]

Claudin-4 is a key component of tight junctions, which play an important role in the formation of the epidermal barrier by forming a circumferential network in the granular layer that serves as a gatekeeper of the paracellular pathway. The aim of this study is to illustrate claudin-4 immunohistochemical staining patterns of different blistering disorders. We collected 35 cases, including two Hailey–Hailey disease, one Darier disease, three Grover disease, one acantholytic acanthoma, two warty dyskeratoma, 11 pemphigus vulgaris (PV) including six mucosal PV, and two pemphigus foliaceus. For comparison, we included five cases of normal skin, five eczema, and three bullous pemphigoid cases. Claudin-4 demonstrated weak-to-moderate expression in keratinocytes located in the stratum granulosum, keratinocytes surrounding hair follicles, and adnexal glands. Further, claudin-4 exhibited moderate-to-strong membranous staining in disrupted keratinocytes surrounding and within the acantholytic and bullous areas in 16/22 of the acantholytic cases (not seen in the six cases of mucosal PV) and all three bullous pemphigoids. This finding suggests that claudin-4 is upregulated in these conditions, which may be a compensatory response to the disrupted barrier function. This finding could shed light on the molecular mechanisms underlying disrupted barrier function in blistering disorders, independent of the specific underlying disease mechanism. [ABSTRACT FROM AUTHOR]

The trichorhinophalangeal syndrome type 1 (TRPS1) immunohistochemical (IHC) stain has increased in use in recent years as a marker for breast carcinomas. The TRPS1 gene is involved in various tissues, including the growth and differentiation of hair follicles. This article seeks to evaluate the IHC expression of TRPS1 in cutaneous neoplasms with follicular differentiation, such as trichoblastoma (TB), trichoepithelioma (TE), and basal cell carcinoma (BCC). IHC studies were performed on 13 TBs, 15 TEs, and 15 BCCs with an antibody against TRPS1. The study found a variable staining expression of TRPS1 in the tumor nests of TB, TE, and BCC. BCCs were distinct in that none of the BCCs demonstrated intermediate or high positivity, while TBs and TEs showed intermediate-to-high positivity in 5/13 (38%) and 3/15 (20%) of cases, respectively. We observed a distinct staining pattern among the mesenchymal cells of TB and TE. We found that TRPS1 highlighted perifollicular mesenchymal cells adjacent to the nests of TB and TE tumor cells. This staining pattern was absent in BCCs, where only scattered stromal cells were positive for TRPS1. Papillary mesenchymal bodies were also highlighted by TRPS1 in TB and TE. TRPS1 stained various parts of the normal hair follicle, including the nuclei of cells in the germinal matrix, outer root sheaths, and hair papillae. TRPS1 may be a useful IHC marker for follicular differentiation. [ABSTRACT FROM AUTHOR]

Leukocytoclastic vasculitis is an inflammatory disease of small blood vessels; circulating immune complexes are part of the disease. A 57-year-old female presented with a sudden appearance of palpable purpura with petechial hemorrhages on the lower limbs after taking multiple medications. Skin biopsies were stained for H&E, direct immunofluorescence (DIF) and immunohistochemistry (IHC). The DIF revealed strong staining with multiple immunoglobulins and other markers in small dermal blood vessels, including those around skin appendices The IHC was positive for myeloperoxidase. CD15, myeloperoxidase and HLA-DPDQDR on the upper dermal blood vessels, as well as on inflammatory cells and debris around the vessels. These findings have not been previously documented and may indicate that circulating immune complexes activate the neutrophils. [ABSTRACT FROM AUTHOR]

Cutaneous T-cell lymphomas (CTCLs) are rare tumors with no established markers that can reliably distinguish between benign and malignant lesions. Preferentially Expressed Antigen in Melanoma (PRAME) is a cancer/testis antigen that is found in many solid and hematologic malignancies. PRAME overexpression typically portends a poor prognosis and lower chemotherapeutic response. To date, no studies have established a role for PRAME in CTCL. An analysis was performed on 47 cases definitively diagnosed as CTCL: 25 cases of mycosis fungoides, 2 of Sezary syndrome, 5 of CD30+ lymphoproliferative disorder, 7 of primary cutaneous anaplastic large T-cell lymphoma, 3 of primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder, 1 of subcutaneous panniculitis-like T-cell lymphoma, and 4 of angiocentric T-cell lymphoma. PRAME immunohistochemistry was completely negative in all cases. PRAME expression was not found in any CTCL subtypes, suggesting that the pathogenesis of CTCL is not mediated by PRAME. Further study is required to identify biomarkers that might aid in the diagnosis and prognostication of CTCLs. [ABSTRACT FROM AUTHOR]