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Head and neck carcinomas with basaloid features can be diagnostically challenging. A common diagnostic issue is the distinction between a basaloid squamous cell carcinoma (bSCC) and a basal cell carcinoma (BCC) of cutaneous origin. This is particularly true in small biopsy specimens where classic architectural and histologic features may be difficult to appreciate. A specific diagnosis is essential because of significant differences in clinical outcome and therapeutic management. Ten resection cases of bSCC and BCC of the head and neck were selected based on primary location and the classic morphologic features that characterize these 2 entities. The following immunohistochemical markers were evaluated: epithelial membrane antigen (EMA), Ber-EP4, CD44, Bcl2, androgen receptor, SOX2, and p16. The strongest statistically significant differences in staining patterns were for EMA, p16, and SOX2. EMA was positive in all bSCCs and negative in all BCCs. SOX2 was positive in all bSCCs and in only 3 out of 10 BCCs. Staining was weak and peripheral in the SOX2-positive BCCs. p16 was positive in 8 out of 10 bSCCs and negative in all BCCs. We conclude that bSCC and BCC of the head and neck can be readily distinguished by a limited panel consisting primarily of EMA, and supported by SOX2 and p16.

Background Skin reactions to the sting of the imported fire ant have characteristic clinicopathological features. Methods One case of experimental envenomation was prospectively followed during 48 hours, with biopsies. In addition, six cases from our laboratory were retrospectively evaluated histopathologically for the following features: spongiosis, exocytosis (and type of cells), pustule formation, erosion/ulceration, epidermal necrosis, scale/crust, papillary dermal edema, inflammatory dermal infiltrate (cell type, density, depth, distribution, shape), red blood cell extravasation, vasculopathy, vasculitis. Results The typical lesion follows a very distinctive clinical and histopathologic evolution over 48 hours, with the formation of a subepidermal pustule overlying a wedge shaped area of dermal collagen basophilic degeneration with scattered neutrophils. In the six cases retrieved from our files, the main features were a superficial and deep dermal, perivascular, periadnexal and interstitial infiltrate consisting of neutrophils, with basophilic degeneration of the collagen. A subepidermal pustule was noted in half of the cases. Conclusions In biopsies taken in a clinical setting, even in the absence of the characteristic subepidermal pustule, the diagnosis of imported fire ant sting can be suspected if there is a superficial and deep perivascular, periadnexal and interstitial infiltrate composed of neutrophils, with some basophilic denaturation of collagen.

First described in 1992, onychomatricoma is a rare, benign, fibroepithelial tumor of the nail matrix with few reported cases in the literature. The tumor predominately affects the fingers of Caucasian women during the 5th decade of life and is typically slow growing and painless. The authors present a unique clinical presentation of a giant onychomatricoma in a darker-skinned 60-year-old South Asian individual who presented with a large dome-shaped nail that was smooth, shiny, and green.

Lichen myxedematosus is a chronic cutaneous mucinosis that can present on a spectrum from localized cutaneous lesions to systemic disease of scleromyxedema. The clinical presentation of localized cutaneous lichen myxedematosus is waxy lichenoid papules, nodules, and/or plaques that have histopathologic findings of mucin deposition and a variable degree of fibroblast proliferation. There is an absence of serum paraproteins, and there are no other systemic causes of cutaneous mucinosis such as thyroid disease. The pathogenesis of lichen myxedematosus is unknown. We report 3 cases of localized cutaneous lichen myxedematosus with a light chain-restricted plasmacytic component by in situ hybridization. Our findings deliver an insight for disease pathogenesis and highlight for the first time, the significance of plasma cells in lesions of localized cutaneous lichen myxedematosus. We suggest that plasma cell light chain restriction could represent a clue to distinguish localized cutaneous disease from systemic disease.

Chromoblastomycosis (CBM) is a slowly progressive cutaneous and subcutaneous mycosis mostly seen in tropical and subtropical areas and Fonsecaea pedrosoi is the most common cause. The authors describe the case of a diabetic Haitian woman, presenting with a chronic verrucous plaque without any history of trauma. Her histopathologic results showed epidermal hyperplasia and sclerotic bodies, which are diagnostic for CBM. Her therapy began with itraconazole 200 mg tablets twice a day. The unique feature of this patient is the coincidence of diabetes and CBM. However, to the best of our knowledge, this is the first documented case of human CBM in Miami, FL, which develops the awareness regarding this diagnosis among doctors in this area. There should be a close communication between dermatologists and pathologists to make an early diagnosis of CBM and also adequate therapy, which both are fundamental to improve patient's quality of life.

Sweet syndrome (SS) is an acute febrile neutrophilic dermatosis that can be associated with malignancy and medications. A 60-year-old man presented with erythematous, edematous, and ulcerated plaques in the extensor surface of the upper extremities, after a ketoconazole course due to pityrosporum folliculitis. Skin biopsy showed a dense dermal neutrophilic infiltrate, associated with marked papillary dermal edema. Blood count showed leukocytosis and neutrophilia. Skin lesions resolved spontaneously with discoloration after 2 weeks of discontinuation of ketoconazole. Although most cases of drug-induced SS are associated with granulocyte colony-stimulating factor, other medications need to be considered. This is the first reported case of ketoconazole-induced SS despite its widespread use.

Skin reactions to the sting of the imported fire ant have characteristic clinicopathological features.One case of experimental envenomation was prospectively followed during 48 hours, with biopsies. In addition, 6 cases from our laboratory were retrospectively evaluated histopathologically for the following features: spongiosis, exocytosis (and type of cells), pustule formation, erosion/ulceration, epidermal necrosis, scale/crust, papillary dermal edema, inflammatory dermal infiltrate (cell type, density, depth, distribution, shape), red blood cell extravasation, vasculopathy and vasculitis.The typical lesion follows a very distinctive clinical and histopathologic evolution over 48 hours, with the formation of a subepidermal pustule overlying a wedge-shaped area of dermal collagen basophilic degeneration with scattered neutrophils. In the 6 cases retrieved from our files, the main features were a superficial and deep dermal, perivascular, periadnexal and interstitial infiltrate consisting of neutrophils, with basophilic degeneration of the collagen. A subepidermal pustule was noted in half of the cases.In biopsies taken in a clinical setting, even in the absence of the characteristic subepidermal pustule, the diagnosis of imported fire ant sting can be suspected if there is a superficial and deep perivascular, periadnexal and interstitial infiltrate composed of neutrophils, with some basophilic denaturation of collagen.

Methotrexate toxicity in mucocutaneous areas is usually not associated with tissue eosinophilia. We describe a case of acute methotrexate-induced mucocutaneous erosions with interface dermatitis and eosinophils. A 76-year-old African-American woman with a history of bullous pemphigoid on methotrexate therapy presented with lower extremity cellulitis, developing oral and cutaneous erosions during hospitalization after daily dosage of methotrexate. Shallow circular cutaneous erosions were found on chest, abdomen and limbs. Laboratory results showed pancytopaenia and elevated liver function tests. Skin biopsy revealed irregular acanthotic epidermis with interface dermatitis, individual dyskeratotic cells and superficial perivascular lymphocytic infiltrate with numerous eosinophils. Methotrexate was stopped and leucovorin was administered, leading to improvement. The histopathological changes in acute mucocutaneous toxicity range from pauci-inflammatory erosions with dyskeratotic keratinocytes to interface dermatitis and infrequently seen eosinophils. This case exemplifies that interface dermatitis with a marked eosinophilic infiltrate can be found in the setting of acute mucocutaneous methotrexate toxicity.

Psoriasis is a chronic, inflammatory autoimmune disease that affects about 3% of the general population in the United States with 17% suffering from moderate to severe psoriasis. The disease process is believed to be mediated by tumor necrosis factor (TNF)-α and cytokines secreted by specialized T-cell populations including Interleukin (IL)-17, IL-22, and Interferon (IFN) γ. IL-17 plays an important role in psoriasis. In this study we evaluated the expression of IL-17A in variants of psoriasis including plaque, palmoplantar, scalp, pustular, and guttate subtypes via immunohistochemistry (IHC).A search of the University of Miami Dermatopathology database was performed to identify all available patient specimens within the various subtypes of psoriasis. IL-17A IHC staining was performed using 4 μm paraffin skin sections. 1:25 dilution of IL-17A antibody was used. Stained slides were analyzed using a semi-quantitative scoring method ranging from negative to three plus.Palmoplantar and pustular psoriasis cases showed consistently strong IL-17A staining. Plaque psoriasis cases showed intermittent to strong IL-17A staining. The results in the scalp and guttate psoriasis cases showed variable results.The results of our study suggests the significant role of the cytokine IL-17A in the development of palmoplantar and pustular psoriasis. However, scalp and guttate subtypes showed variable expression from negative to strongly positive, which demonstrates a case by case basis expression of IL-17A. Therefore, exploring the IHC characterization of subtypes of psoriasis will help dermatologists better understand the pathogenesis of each subtype and help clinicians optimize treatments.

Matrical carcinoma (pilomatrix carcinoma) is a rare follicular low-grade malignancy with matrical differentiation. A pigmented variant with admixed dendritic melanocytes is exceedingly rare with only 7 cases reported in the literature. The diagnosis of malignancy can be difficult to establish. The authors report a case of a 79-year-old woman with a matrical carcinoma who presented with an ulcerated nodule on the posterior right leg, measuring 2.2 cm in greatest dimension. The excisional biopsy showed irregularly shaped dermal and subcutaneous nodules ranging in size from 0.1 to 0.5 cm. The nodules were composed of aggregates of large atypical basaloid cells, with multiple, sometimes atypical, mitoses, admixed with ghost cells, and central necrosis en masse. In addition, the neoplasm was characterized by focal marked melanocytic proliferation and multiple whorls of pink eosinophilic material reminiscent of keratin pearls (squamoid whorls). The basaloid cells were positive for beta-catenin both in the nuclei and the cytoplasm and negative for BerEp4. S100, Melan-A, and HMB45 highlighted the melanocytic dendritic cells. Pan-cytokeratin was negative in the ghost cells and focally positive in the squamoid whorls. Squamoid whorls seem to be a significant feature of matrical carcinoma.

Extramammary Paget disease of the vulva accounts for 1%–2% of the neoplasms of the anogenital area. Very rarely, extramammary Paget disease of the vulva has been associated with an underlying mammary-like carcinoma, usually ductal, extremely rarely mixed ductal and lobular. We report the case of a 60-year-old female with a recurrent extramammary Paget disease of the vulva. Pathological examination of the wide excision of the vulva revealed an extramammary Paget disease with an underlying invasive carcinoma composed of medium size cells organized in single files, a morphology similar to that of an invasive lobular breast carcinoma. Immunohistochemical staining showed a comparable profile in the Paget cells and in the invasive tumoral cells: CEA and CK7 positivity; GCDFP-15, ER focal positivity. E-cadherin and HER2 were diffusely positive. S100 and CK20 were negative. HER2-CISH was amplified. The diagnosis of extramammary Paget disease of the vulva with an underlying mammary-like lobular carcinoma was made. Despite the characteristic lobular features, the immunohistochemical profile differs from the typical profile of a lobular carcinoma of the breast. The implications in term of prognostic and therapeutic significance need to be further studied.

• Background.— Toxic epidermal necrolysis is a potentially severe mucocutaneous affliction whose cause is usually drug related. To further characterize the nature of the dermal mononuclear infiltrate as well as the epidermal alterations observed by standard microscopy, we studied five cases of toxic epidermal necrolysis using labeled monoclonal antibodies. Results.— On clinically involved areas of skin, the following occurs: (1) the dermal infiltrate is composed mainly of activated T lymphocytes, with a predominant helper phenotype; (2) the number of Langerhans cells is decreased; and (3) keratinocytes express HLA-DR molecules, normally absent on their surface. Conclusions.— These findings, although not specific, are consistent with an immune cellular reaction, but they could also be linked to an inflammatory reaction initiated by epidermal damages whatever its primary mechanism. ( Arch Dermatol. 1992;128:50-53)

Acute graft-versus-host reaction after allogeneic bone marrow transplantation has been reported to induce toxic epidermal necrolysis. To assess the respective role of acute graft-versus-host disease and of drug reaction in this setting, we retrospectively reviewed nine cases of toxic epidermal necrolysis that occurred in a series of 152 allogeneic bone marrow recipients. In five cases visceral involvement was suggestive of acute graft-versus-host disease without any drug more than "doubtfully" suspected. In four cases extracutaneous symptoms were absent or mild and suspect drugs (mainly sulfonamides) had been administered with a timing suggestive of "possible" causality. All nine patients died, mainly from infection possibly aggravated by high doses of corticosteroids. We conclude that toxic epidermal necrolysis may be more frequent than generally thought after bone marrow transplantation and has a poor prognosis. It seems to be related to a drug reaction to sulfonamides as often as to acute graft-versus-host disease.

In Reply.— We thank Dr Koff for pointing to some differences between the results of several recent studies on the immunopathology of toxic epidermal necrolysis (TEN). As did other investigators, we observed the abnormal expression of HLA-DR by keratinocytes, a dermal infiltrate composed of T lymphocytes, mainly CD4 + , and the absence of cells with a phenotype of natural killer cells. 1 The main difference concerns the nature of the epidermal infiltrate. We observed a similar number of CD4 + and CD8 + mononuclear cells within the epidermis, while other investigators reported that all or most of the cells in the epidermis were CD8 + . 2,3 We suggest that these divergent findings resulted less from different case definition than from the different timing of the biopsies. We obtained biopsy specimens from "early" erythematous lesions, distinct from the areas of epidermal sloughing. Our pathologic samples exhibited little or no morphologic alteration of epidermal cells, in contrast

• Blister formation in skin graft donor or recipient sites is uncommon. We describe a 49-year-old female patient with bullae in sites of grafts used in the treatment of toxic epidermal necrolysis. Generalized loss of skin developed 3 weeks after she had ingested phenobarbital. Sixty days after the beginning of the toxic epidermal necrolysis, the reepidermization was only 80% and skin grafts were placed on lower-extremity and abdominal wounds using the first healed sites as donor sites. Several bullae and erosions were noted on grafted areas 3 weeks later. Skin biopsy specimens revealed separation at the dermoepidermal junction, and no autoantibodies were detected by direct and indirect immunofluorescence. Electron microscopy demonstrated that the blister was formed through the basal keratinocytes and that the dermoepidermal junction, including hemidesmosomes and anchoring fibrils, was normal. Immunofluorescence mapping was performed using polyclonal antibodies from the serum of patients with bullous pemphigoid and epidermolysis bullosa acquisita and monoclonal antibodies against GB3 antigen and collagen type VII. All but the bullous pemphigoid serum gave positive results; only faint and focal staining of the dermoepidermal junction was observed with bullous pemphigoid serum. These findings are the same as those encountered in hereditary epidermolysis bullosa simplex. A biopsy performed 1 year later in the same site as the first one revealed that bullous pemphigoid antigen was normally expressed. Keratinocytes autografted in the treatment of toxic epidermal necrolysis may become transiently, functionally abnormal because of the alteration of recipient sites. ( Arch Dermatol. 1991;127:1369-1374)

Leprosy (Hansen's disease) is a chronic contagious granulomatous disease principally affecting the skin and peripheral nervous system, caused by Mycobacterium leprae. In this report, we present a case of autochthonous leprosy in a man from Florida as the first human case reported from this region. Authors believe dermatologists need to be aware of the possibility of autochthonous transmission of leprosy in the Eastern-Southern United States, and should consider leprosy in any patient with atypical skin lesions, even when a history of contact with armadillo is missing.