Neoplasms of sweat glands and the breast may be morphologically and immunophenotypically similar. A recent study showed that TRPS1 staining is a highly sensitive and specific marker for breast carcinoma. In this study, we analyzed TRPS1 expression in a spectrum of cutaneous sweat gland tumors. We stained five microcystic adnexal carcinomas (MACs), three eccrine adenocarcinomas, two syringoid eccrine carcinomas, four hidradenocarcinomas, six porocarcinomas, one eccrine carcinoma-NOS, 11 hidradenomas, nine poromas, seven cylindromas, three spiradenomas, and 10 syringomas with TRPS1 antibodies. All of the MACs and syringomas were negative. Every cylindroma and two of the three spiradenomas demonstrated intense staining in cells lining the ductular spaces, with negative to relatively weak expression in surrounding cells. Of the 16 remaining malignant entities, 13 were intermediate to high positive, one was low positive, and two were negative. From the 20 hidradenomas and poromas, intermediate to high positivity was revealed in 14 cases, low positivity in three cases, and negative staining in three cases. Our study demonstrates a very high (86%) expression of TRPS1 in malignant and benign adnexal tumors that are mainly composed of islands or nodules with polygonal cells, e.g., hidradenomas. On the other hand, tumors with small ducts or strands of cells, such as MACs, appear to be completely negative. This differential staining among types of sweat gland tumors may represent either differential cells of origin or divergent differentiation and has the potential to be used as a diagnostic tool in the future.
Digital papillary adenocarcinoma (DPA) is a rare neoplasm that can exhibit local recurrence and distant metastasis. We present a series of eight cases of DPA showing two distinct clinical presentations, morphologies, immunophenotypes, and molecular features.Four cases were characterized by painless, slow-growing nodules located on the digits.The lesions were small, well-defined, and confined in the dermis. Histopathologically, these tumors were composed of glandular structures lined by cuboidal epithelium with luminal papillary infoldings. Only rare mitotic figures and minimal squamoid differentiation were present, and cellular necrosis was absent. All four cases were positive for the BRAF V600E immunohistochemistry but negative for p16, low-risk and high-risk HPV in situ hybridization (ISH). In contrast, the remaining four cases were characterized by painful, rapidly growing masses on the digits. These four lesions were located in the deep dermis and consisted of a solid, tightly packed papillary architecture lined by atypical epithelioid cells with inconspicuous nucleoli. Cellular necrosis, numerous mitotic figures, and prominent squamoid differentiation were seen. All cases were negative for the BRAF V600E IHC. However, they showed strong, patchy to diffuse reactivity for p16 and were positive for low-risk HPV ISH and negative for high-risk HPV ISH. Our findings suggest that the current classification of DPA encompasses tumors that show two discrete pathogenic pathways -BRAF mutation or low-risk HPV infection. DPAs with low-risk HPV infection exhibit aggressive clinical features, high-grade morphology, marked squamoid differentiation, and wild-type BRAF. DPAs with BRAF V600E have less aggressive clinical features, low-grade morphologic findings, mild to absent squamoid differentiation, and negative HPV infection.
Cutaneous eruptions associated with hemophagocytic lymphohistiocytosis (HLH) have been reported in 6%-63% of patients. Clinical findings of these skin lesions vary widely and include maculopapular rashes, ulcers, and violaceous nodules. Corresponding histologic findings are also variable and are considered nonspecific. We report the case of a 4-year-old boy who initially developed a widespread popular-pustular rash 2 weeks after his 12month measles, mumps, and rubella vaccinations. These resolved with scarring then recurred following his 24-month vaccinations. Multiple skin biopsies were negative for infectious organisms and showed a granulomatous infiltrate with perforation and necrobiosis. The differential diagnosis included perforating granuloma annulare, infection, or rheumatoid nodules. At the age of 4, he developed fever, hepatosplenomegaly, pancytopenia and other laboratory abnormalities, requiring hospitalization. A number of studies were performed including biopsies of bone marrow and liver. Molecular testing revealed 2 mutations in UNC13D known to be associated with familial HLH. His prior cutaneous lesions were likely caused by immune dysregulation exacerbated by immunizations because of underlying familial HLH. This case illustrates the importance of recognizing an unusual cutaneous manifestation of a rare disease to arrive at an earlier diagnosis in a pediatric patient. Although cutaneous eruptions usually develop concurrently with other systemic symptoms of HLH, preceding unusual skin lesions may be the first indication of this rare disease.
Melanocytic nevi existing in lymph nodes create a diagnostic challenge by mimicking metastases. PReferentially expressed Antigen in MElanoma (PRAME) immunohistochemical (IHC) stain can differentiate one from another. FLI‐1 IHC expression has been shown in malignant melanoma with variable sensitivity while melanocytic nevi were reported to be negative. We hypothesized that FLI‐1/Melan‐A dual IHC staining may be used in the distinction of metastatic melanoma from nodal nevi and can be an alternative and/or complementary to PRAME. In this study, we examined 13 lymph nodes with metastatic melanoma and 13 lymph nodes with benign deposits. We stained all of the lymph nodes with FLI‐1, FLI‐1/Melan‐A dual, and PRAME IHC stains. In addition, we stained paired skin samples of the metastatic lymph nodes with FLI‐1 and PRAME. In primary cutaneous melanomas, 11 of 13 were positive for FLI‐1 and PRAME expression (85%). Malignant cells in 12 and 13 lymph nodes showed positive expression of PRAME and FLI‐1, respectively. Only one case with a nevic cell deposit was weakly positive for FLI‐1 and the remaining benign cases were negative for both FLI‐1 and PRAME. Our results show that FLI‐1/Melan‐A dual stain is as sensitive and specific as PRAME in distinguishing lymph nodes with metastatic melanoma from nodal nevi. Further studies with larger case numbers are needed to support our significant results.
Plasmacytoid dendritic cells (pDCs) constitute a subset of dendritic cells known to be the “professional” interferon type I (IFN-I) producers. pDCs play an important role in antiviral immunity, as well as linking innate and adaptive immunity. Under normal conditions pDCs are not present in skin. They are shown to be a part of the inflammatory infiltrate in different skin conditions including erythema multiforme (EM). This condition is considered to be a cell-mediated immune reaction to a wide variety of agents, most commonly herpes simplex virus. Nevertheless, the pathophysiology of EM still remains unclear. In this study, we grouped 32 biopsies from 30 patients diagnosed with EM, based on their etiology and analyzed the density and distribution of CD123 positive pDCs. In all cases we observed a greatly increased number of pDCs in the dermal inflammatory infiltrate. Virally-induced EM (by herpes simplex virus (HSV) and other viruses) was more likely to have a significantly higher number of pDCs compared to non-virally associated EM. Hence, we think that pDCs play a key role in the pathogenesis of EM independent of etiology and may play an increased role in virally-associated cases. Further studies on pDCs would clarify their importance in EM and improve our understanding of the pathophysiology of this disease.
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