Urticarial mycosis fungoides: A distinctive presentation with blood involvement and a peculiar immunophenotype.

Mycosis fungoides (MF) has been widely reported to mimick a considerable number of different dermatoses, including scarring alopecia, bullous dermatoses or cysts, and comedones. In atypical presentations, histopathology is essential for the diagnosis. We present two cases of MF with clinical urticarial lesions and a striking blood involvement that responded to mogamulizumab treatment. Histopathologically, both cases had classic MF features and shared a peculiar immunophenotype, with positivity for CD25 and FOXP3. Differential diagnoses included urticarial lymphomatoid drug reactions and other lymphomas, like T-cell prolymphocytic leukemia, atypical Sézary syndrome, or adult T-cell lymphocytic leukemia. A low suspicion threshold is necessary for the diagnosis of atypical presentations of MF.

Clinical, histopathologic, immunohistochemical, and electron microscopic findings in cutaneous monkeypox: A multicenter retrospective case series in Spain.

BACKGROUND: The worldwide outbreak of monkeypox has evidenced the usefulness of the dermatologic manifestations for its diagnosis. OBJECTIVE: To describe the histopathologic and immunohistochemical findings of monkeypox cutaneous lesions. METHODS: This is a retrospective histopathologic and immunohistochemical study of 20 patients with positive Monkeypox virus DNA polymerase chain reaction and immunohistochemical positivity for Vaccinia virus in cutaneous lesions. Four cases were also examined by electron microscopy. RESULTS: The most characteristic histopathologic findings consisted of full-thickness epidermal necrosis with hyperplasia and keratinocytic ballooning at the edges. In some cases, the outer root sheath of the hair follicle and the sebaceous gland epithelium were affected. Intraepithelial cytoplasmic inclusion bodies and scattered multinucleated keratinocytes were occasionally found. Immunohistochemically, strong positivity with anti-Vaccinia virus antibody was seen in the cytoplasm of ballooned keratinocytes. Electron microscopy study demonstrated numerous viral particles of monkeypox in affected keratinocytes. LIMITATIONS: Small sample size. Electron microscopic study was only performed in 4 cases. CONCLUSION: Epidermal necrosis and keratinocytic ballooning are the most constant histopathologic findings. Immunohistochemical positivity for Vaccinia virus was mostly detected in the cytoplasm of the ballooned keratinocytes. These findings support the usefulness of histopathologic and immunohistochemical studies of cutaneous lesions for diagnosis of monkeypox.

Median raphe cysts: A clinico-pathologic and immunohistochemical study of 52 cases.

BACKGROUND: Median raphe cysts (MRC) are epithelial-lined cystic lesions of the genital area that do not communicate with the urethra or the overlying epidermis. Immunohistochemically, MRC show positivity for cytokeratin (CK) 5-6, CK 7, carcinoembryonic antigen, p63 and uroplakin III (URO III). GATA3 and human milk fat globulin 1 (HMFG1) are immunohistochemical markers that have been not previously studied in MRC. METHODS: We conducted a study of 52 patients diagnosed with MRC in the Pathology Departments of eight hospitals between 1990 and 2016. The monoclonal antibodies used were CK5-6, CK7, CK20, URO III, p63, GATA3, and HMFG1. HMFG1 was studied in five cases of apocrine hidrocystomas and compared with five cases of MRC from our series. RESULTS: CK 5-6, CK7, and p63 expression showed strong positivity in the urothelial epithelium of 48 cases. CK20 was focally positive in areas of mucinous differentiation in three cases. GATA3 showed intense nuclear staining in 30 cases. HMFG1 was positive in three cases of MRC and in three cases of apocrine hidrocystoma. CONCLUSION: Positivity of GATA3 and CK7 in MRC supports the urothelial origin of these cysts. We found no differences in HMFG1 expression between MRC and apocrine hidrocystomas.

Foamy Cell Histiocytosis Is a Diagnostic Pitfall: A Case Report of Xanthomatosis Secondary to Sitosterolemia Mimicking Progressive Nodular Histiocytosis.

ABSTRACT: We report a noteworthy case of a 10-year-old girl who presented with papular and nodular lesions on the skin that were clinically and histologically mistaken for progressive nodular histiocytosis. During the clinical management of the patient, the high lipid levels raised the suspicion of lipid metabolism disease and helped us to make the correct diagnosis of sitosterolemia. In sitosterolemia, proper management such as restriction of plant sterol intake and administration of cholesterol absorption inhibitor can improve prognosis.

Histopathology of Dermatologic Complications of Tattoos.

ABSTRACT: Tattoos are characterized by the introduction of exogenous pigments into the dermis. Tattoos usually serve cosmetic purposes, although they may have other causes, such as traumatic pigment implants in accidents or medical-related tattoos in the context of radiotherapy. Dermatologic adverse reactions are relatively uncommon, and they include infections, immune-mediated reactions, cutaneous lesions secondary to the Koebner phenomenon, exacerbation of preexisting dermatosis, benign and malignant neoplasms, and a miscellaneous group of dermatologic conditions that may appear in a preexisting tattoo. The aim of this study is to review the types of histopathologic reactions that may appear in a preexisting permanent tattoo.

Localized Acral Sclerosing Langerhans Cell Histiocytosis: A New Form of Presentation of Cutaneous Langerhans Cell Histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare proliferative disorder, more frequent in children, characterized by an abnormal accumulation of Langerhans cells admixed with eosinophils, lymphocytes, neutrophils, and macrophages. The clinical presentation is variable and depends on whether a single or multiple organs are affected. Skin lesions are common in LCH (40% of cases) and represent a frequent form of presentation (in up to 80% of cases). Cutaneous manifestations of LCH are highly variable, frequently presenting as crusted papules or scaly seborrheic-like lesions localized in the scalp. We report the first case of a localized acral sclerosing LCH, a new form of LCH. This case highlights the broad and surprising form of presentation of LCH which may be overlooked and can significantly delay its diagnosis. The development of systemic disease may occur months to years after the initial skin presentation. Prompt diagnosis and treatment may prevent progression to systemic disease, as documented in some cases.

Perineural Invasion as a Clue to Malignant Behavior in a Dermatofibroma.

Dermatofibroma (DF) represents one of the most common mesenchymal proliferations of the skin. Their recurrence rate, even when incompletely excised, is very low, whereas the atypical, aneurysmal, and cellular variants have recurrence rates of up to 20% each. Extraordinary rare malignant lesions with metastases to lymph nodes and/or lung have been described. We report a 64-year-old woman with a long history (years) of a skin lesion on her right arm that became painful during the last months. Histologically, it consisted of a conventional cellular DF in which perineural invasion was present. Subsequently, the lesion showed a clinically aggressive course with recurrences, sarcomatous transformation, and pulmonary metastases. Given that no predictive morphological features have been identified to separate classical benign DF from rare metastasizing forms, perineural invasion in an otherwise conventional DF could be a histopathologic clue for an adverse prognosis and should provoke a closer clinical follow-up.

Combination of Congenital and Deep Penetrating Nevus by Acquisition of ß-Catenin Activation.

Deep penetrating nevus (DPN) is an intradermal, sometimes compound benign melanocytic lesion, which involves the reticular dermis, occasionally reaching the subcutis, which can raise concern for melanoma both clinically and histologically. Recently, it has been genetically defined by the combination of MAPK activating and ß-catenin activating mutations. We sought to investigate genetic alterations in 2 cases of combined nevi of congenital melanocytic and DPN. Case 1 was a 16-year-old woman with a pigmented lesion on the trunk since birth, which was completely excised. Histopathological examination revealed a combined congenital nevus with a DPN. Comparative genomic hybridization showed no major genetic alterations, except for gain of 6q11.1 and point mutation of B-RAF V600E. Case 2 was a 62-year-old woman with a congenital pigmented lesion on the back. The lesion was diagnosed as a combined nevus of congenital and DPN. Comparative genomic hybridization showed no genetic alterations, and the NRAS Q61K was detected in both components. DPN is in most cases part of a combined nevus. Our cases showed strong and uniform nuclear expression of ß-catenin and cyclin D1 in the DPN component suggesting the evolution of the congenital nevus to the DPN clone by acquiring ß-catenin activating mutation.

Proliferating Neurocristic Hamartoma Arising in a Giant Congenital Nevus: Comparative Genomic Hybridization Findings.

Neurocristic cutaneous hamartomas (NCHs) are rarely reported tumors with divergent differentiation derived from persistently active pluripotent cells from the neural crest. They result from aberrant development of the neuromesenchyme, and they can express fibrogenic, melanocytic, and/or neurosustentacular differentiation. Thus, congenital melanocytic nevus also represents a neurocristic dysplasia of the skin in which cells are melanogenic cells arrested in development located in the reticular dermis, and nodular proliferative neurocristic hamartoma may arise within a congenital melanocytic nevus. The real importance of NCHs is that, although few cases have been reported in the literature, some cases have shown development of melanoma. Moreover, the only previously reported case of a similar "proliferative neurocristic nodule" analyzed with comparative genomic hybridization showed an aberration pattern similar to melanoma. We present a rare case of NCH associated with a congenital nevus in a 7-year-old boy, with classical histological and immunohistochemical features suggesting a "proliferative neurocristic hamartoma". Comparative genomic hybridization assay showed that chromosomal aberrations were absent in the congenital nevus, whereas, interestingly, the proliferative neurocristic proliferation had an aberration pattern similar to proliferative nodules with gains or losses of entire chromosomes only, similar to typical proliferative nodules and supporting the benign behavior of this lesion.