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Background Panniculitis occurring in dermatomyositis is uncommon, with only a few cases described in the literature, most of them as case reports. Objective This report describes the clinicopathological and immunohistochemical findings in a series of 18 patients with panniculitis associated with dermatomyositis. Methods In each patient, we collected the clinical data of the cutaneous lesions as well as the characteristic clinical and laboratory findings. A series of histopathologic findings was recorded in the biopsy of each patient. A panel of antibodies was used in some cases to investigate the immunophenotype of the infiltrate. Data of treatment and follow-up were also collected. Results Of the 18 patients, 13 were female and 5 were male, ranging in age from 13 to 74 years (median, 46.4 years). In addition to panniculitis, all patients presented pathognomonic cutaneous findings of DM and reported proximal muscle weakness prior to the diagnosis of panniculitis. Muscle biopsy was performed in 17 patients and MRI in one, all with the diagnosis of inflammatory myopathy. None of the patients presented any associated neoplasia. Panniculitis lesions were located in the upper or lower limbs. Histopathology showed a mostly lobular panniculitis with lymphocytes as the main component of the infiltrate. Most cases showed also numerous plasma cells and lymphocytes surrounding necrotic adipocytes (rimming) were frequently seen. Lymphocytic vasculitis and abundant mucin interstitially deposited between collagen bundles of the dermis were also frequent findings. Late-stage lesions showed hyaline necrosis of the fat lobule and calcification. Immunohistochemistry demonstrated that most lymphocytes of the infiltrate were T-helper lymphocytes, with some B lymphocytes in the lymphoid aggregates and small clusters of CD-123-positive plasmacytoid dendritic cells in the involved fat lobule. Conclusion Panniculitis in dermatomyositis is rare. Histopathologic findings of panniculitis dermatomyositis are identical to those of lupus panniculitis. Therefore, the final diagnosis requires clinic-pathologic correlation. [ABSTRACT FROM AUTHOR]

Abstract: Microcystic adnexal carcinoma (MAC) is a low-grade malignant neoplasm of slow growth and low metastatic potential, but locally aggressive. Architecturally, MAC is usually a poorly circumscribed neoplasm that tends to extend deeply into the dermis and subcutaneous tissue. We present here a lesion in which the histopathologic study showed a well-demarcated nodular lesion involving the mid dermis and composed of small cystic keratinous structures, solid aggregates of pale squamous cells without cytologic atypia and ductal structures. Although these neoplastic components resembled those of MAC, the sharp delimitation of the lesion as well as the absence of deep extension and perineural involvement supported the benign nature of this lesion. We have named this neoplasm microcystic adnexal adenoma, as the benign counterpart of MAC., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Despite new horizons opened by recent advances in molecular pathology, histological evaluation still remains the diagnostic gold standard regarding cutaneous melanocytic neoplasms. Several histological variants of melanoma have been described, and their knowledge is crucial for accurate diagnosis and classification of cases with unusual clinico-pathological features. Uncommon histological variants of melanoma have been described based on a broad constellation of features, including architectural pattern, stromal alterations, cytological attributes, and other morphological properties. This review is aimed at providing an extensive discussion of unusual but distinctive histopathological variants of melanoma.

Despite new horizons opened by recent advances in molecular pathology, histological evaluation still remains the diagnostic gold standard regarding cutaneous melanocytic neoplasms. Several histological variants of melanoma have been described, and their knowledge is crucial for accurate diagnosis and classification of cases with unusual clinicopathological features. Uncommon histological variants of melanoma have been described based on a broad constellation of features, including architectural pattern, stromal alterations, cytological attributes, and other morphological properties. This review is aimed at providing an extensive discussion of unusual but distinctive histopathological variants of melanoma.

Even though malignant melanoma accounts for 4 % of all skin cancers, it is the type responsible for most deaths. The pathogenesis of melanoma is currently not well understood, although an interaction of environmental and genetic factors doubtlessly plays a role. Molecular biology in medicine has progressed increasingly rapidly in recent years. In dermatology, application of molecular biology techniques to the study of malignant melanoma has led to important advances in our knowledge of the main molecular pathways implicated in its development. These findings not only can improve our knowledge of the pathogenesis of the disease but may also have practical implications. Thus, molecular characterization of malignant melanoma may be of great help in differentiating between benign and malignant melanocytic lesions when histopathological features prove insufficient as is the case, for example, in Spitz nevus and spitzoid melanoma. In addition, knowledge of the abnormal molecular pathways in different malignant melanoma lesions can point to new therapeutic targets for treating patients with melanomas with distant metastases, in whom current chemotherapy has failed to extend life expectancy. At present, lack of availability is the main barrier to use of these techniques in dermatology--they are often limited to research, so not generally available in most hospitals. This problem will, however, be overcome when the molecular patterns become standardized, allowing a prognostic and therapeutic characterization of this important disease.

Animal type melanoma is a rare histopathologic variant of melanoma characterized by sheets and nodules of heavily pigmented epithelioid melanocytes that involve the entire thickness of the dermis. This human neoplasm mimics melanocytic neoplasms seen in gray horses and laboratory animals; thus, is termed animal type melanoma. It is quite rare and, with only a few reported cases, its biological behavior is not well understood. We report an example of animal type melanoma on the back of a 27-year-old man. The lesion showed areas of melanoma in situ, which ruled out the possibility of metastatic melanoma. Features of regression were also seen at dermo-epidermal junction and papillary dermis. In some areas, neoplastic melanocytes exhibited a balloon-cell appearance; in others the neoplasm was composed of sheets and fascicles of heavily pigmented epithelioid melanocytes that permeated the entire dermis and extended into the dermal-subcutaneous interface, mimicking a cellular blue nevus. Epithelioid melanocytes in deeper areas showed abundant, heavily pigmented cytoplasm and pleomorphic nuclei with prominent eosinophilic nucleoli and some mitotic figures. The neoplastic cells did not show evidence of maturation in deeper areas of the lesion. In some sections, a nodule of heavily pigmented epithelioid melanocytes was seen far from the main bulk of the lesion, at the dermal-subcutaneous interface, raising the possibility of a satellite lesion. A lymphoscintigraphy showed a sentinel lymph node in the right axilla and a subsequent axillary lymphadenectomy demonstrated that the architecture of the sentinel lymph node was effaced by metastatic melanoma. The patient received adjuvant chemotherapy with inteferon alfa-2b and four months after this treatment the patient is alive and well, without evidence of recurrences or additional metastases.

Pseudosclerodermatous panniculitis is an unusual variant of panniculitis that results as a complication of megavoltage radiotherapy. Four women developed this unusual entity on the anterior chest and abdominal skin after receiving megavoltage therapy for either breast carcinoma or painful bone metastases from breast carcinoma. Histopathologically, the epidermis and dermis of the involved area showed little or no evidence of radiodermatitis. The main findings were confined to the subcutaneous tissue and consisted of thickened, sclerotic septa composed of both thick and thin collagen bundles, and a lobular panniculitis characterized by lipophagic granulomas and scattered lymphocytes and plasma cells. Additionally, one of the cases showed markedly dilated vascular spaces with the appearance of lymphatics in the upper part of the dermis. Pseudosclerodermatous panniculitis after irradiation is an unusual cutaneous complication of megavoltage radiotherapy that should be distinguished from subcutaneous metastatic disease, cellulitis, or connective tissue diseases involving the subcutaneous fat. The differential diagnosis can be established on the basis of the characteristic histopathologic features of postirradiation pseudosclerodermatous panniculitis.

Background: Angiocentric cutaneous T-cell lymphomas of childhood (ACTCLC) are an unusual type of T-cell lymphomas that present with a vesiculopapular eruption mimicking hydroa vacciniforme. Most patients have been children from Asia and Latin America., Objective: The purpose of this study was to describe four cases of ACTCLC; to discuss its clinical, histopathologic, and immunohistochemical features; to consider its possible relationship to the Epstein-Barr virus (EBV); and to clarify its classification within the spectrum of angiocentric lymphomas., Methods: The clinical, histopathologic, and immunohistochemical features of four cases of ACTCLC were identified and analyzed. In addition in situ hybridization for EBV was performed in all cases., Results: The clinical features were similar to previous cases reported under different names, such as hydroa-like lymphomas, edematous, scarring vasculitic panniculitis. Histologically, all showed angiocentric infiltrates composed mainly of T cells. In all cases there were variable numbers of CD30+ cells. The EBV was present in three of the cases., Conclusion: ACTCLC is a distinct type of T-cell lymphoma. It affects mainly children, and the EBV appears to play a role in the pathogenesis of this disease.

Malignant peripheral nerve sheath tumors (MPNSTs) encompass a wide and unusual group of neoplasms with features of neural differentiation. They most commonly present as spindle cell neoplasms and it can be difficult to differentiate them from other spindle cell neoplasms such as leiomyosarcomas, fibrosarcomas and synovial sarcomas. Strict criteria need to be applied in order to make the diagnosis of MPNSTs. Helpful features include contiguity with a nerve or an association with von Recklinghausen disease. The use of immunohistochemical stains may also help to confirm the diagnosis. Markers such as S-100 protein, neurofilament, epithelial membrane antigen and Leu-7 (CD57) are frequently used to assess neural differentiation in these neoplasms. In addition to the spindle cell pattern, MPNSTs may also display an epithelioid pattern. Rarely, other elements may be seen including glands in the so-called glandular MPNST or muscle in triton tumors. In more unusual cases cartilage, adipose tissue and even bone are present. Also included in the group of MPNSTs are the peripheral neuroepithelial tumor, neurotropic or desmoplastic melanomas and malignant granular cell tumors. MPNSTs are highly aggressive tumors and should be treated accordingly.

Glomangiosarcoma is a rare malignant variant of the glomus tumor (GT). It has been reported in different anatomical locations, with only 1 report of its localization to the hand, despite the fact that its benign counterpart is most frequently found there. There is only 1 report of glomangiosarcoma that has metastasized. Special attention should be paid to GTs that are not well circumscribed, since the possibility of persistence and malignant transformation is increased in these lesions. The treatment of choice for glomangiosarcomas is wide local excision.

Metastatic Crohn's disease is the term used for granulomatous lesions of Crohn's disease involving sites other than the gastrointestinal tract. Metastatic Crohn's disease has been considered uncommon, when in actuality it may simply be underdiagnosed or misdiagnosed since the clinical findings can be different. We report on three patients with this condition: one with generalized plaques, another with perineal and perianal ulcerations, and a third with a painless forearm nodule.

Erythema elevatum diutinum (EED) is a rare cutaneous condition that initially presents as leukocytoclastic vasculitis (LCCV) of the skin and later resolves with fibrosis. In addition to the LCCV, EED may show features reminiscent of other entities. For example, it may mimic lesions of dermatofibroma, granuloma annulare, granuloma faciale, or dermatitis herpetiformis. For this study, we reviewed the clinical records and 13 skin biopsies in eight patients with EED. One of the patients had concurrent pityriasis rubra pilaris, and another developed lesions of EED following and at the sites of mosquito bites; these associations have not been noted previously. In addition to such typical histopathological features as diffuse dermal involvement by neutrophils, eosinophils, and leukocytoclastic vasculitis, we also found two unusual patterns. The first was characterized by palisaded necrotizing granulomas, as previously described and associated with Churg-Strauss granuloma; the second condition simulated a pyogenicgranuloma--like lesion.

Anaplastic carcinomas of the pancreas are considered variants of ductal adenocarcinoma. They typically occur in elderly men. They have rarely been reported to occur in association with mucinous cystic neoplasms of the pancreas. We report a case of anaplastic carcinoma occurring in association with a pancreatic mucinous cystic neoplasm, borderline-type, in a 25-year-old woman who presented with lymph node and hepatic metastases.

Background: Follicular mycosis fungoides (FMF) is a recently described variant of cutaneous T-cell lymphoma, histopathologically characterized by infiltrates of atypical CD4+ T lymphocytes around and within the epithelium of the hair follicles (folliculotropism). To date, only four cases of FMF have been reported., Objective: Our goal was to identify cases of FMF and compare them with those previously reported., Methods: The clinical and histopathologic features of three cases of FMF were analyzed. In addition, in one case immunohistochemical analysis in paraffin-embedded and frozen tissue as well as genotypic studies were performed., Results: The three reported cases showed typical histologic findings of FMF, namely, perifollicular and intrafollicular infiltrates of atypical lymphocytes, in the absence of either epidermotropism or follicular mucinosis. Clinically, the lesions were similar to classic MF, but also contained follicular papules. Immunohistochemistry and gene rearrangement studies showed findings similar to classic MF., Conclusion: FMF is a rare variant of cutaneous T-cell lymphoma. Including our three cases, only seven patients have been reported. We hypothesize that the follicular epithelium in patients with FMF may express increased levels of skin-selective homing receptors and adhesion molecules. These may be involved in the induction of the folliculotropism of atypical lymphocytes.

Cutaneous immunocytoma are low-grade B-cell lymphomas, which affect the skin either primarily or secondarily. Primary cutaneous immunocytomas usually present with one or a small number of lesions, mainly in the extremities. They generally remain confined to the skin. Histologically, there are polymorphous infiltrates of cells, in which the presence of monoclonal plasma cells is characteristic. We describe a case of cutaneous immunocytoma with secondary spread to the gastrointestinal tract.

Background and Design: Lymphomatoid papulosis (LyP) and cutaneous Hodgkin's disease share many clinical, histopathologic, and immunohistochemical features. Epstein-Barr virus (EBV) has been implicated in the pathogenesis of several lymphoid malignancies, including Hodgkin's disease. Given the similarities between LyP and Hodgkin's disease, we asked if EBV could be detected in lesions of LyP. We examined 31 specimens of LyP that were obtained from 24 patients for evidence of EBV by in situ hybridization to EBER1 transcripts and for immunohistochemistry of viral latent membrane protein 1 (LMP1)., Results: In no instance there was there any evidence of EBV gene products by either in situ hybridization or immunohistochemistry., Conclusions: The absence of EBV in LyP suggests that this virus is not operative in the pathogenesis of LyP. Furthermore, it suggests that LyP and Hodgkin's disease may not share the same molecular mechanisms despite their phenotypic similarities.

Juvenile xanthogranuloma (JXG) is a benign histiocytic proliferation of uncertain histogenesis which usually resolves spontaneously. Histopathologically, classic lesions are characterized by diffuse proliferations of foamy histiocytes, many of which may be multinucleated (Touton cells), admixed with lymphocytes and eosinophils. Histologic variants of JXG, perhaps representing evolving lesions, may lack these typical histopathological features, showing diffuse infiltrates of non-foamy mononuclear histiocytes without Touton cells, posing problems in differentiation from other histiocytic or melanocytic proliferations. Immunohistochemically, JXG is characterized by variable expressions of several histiocytic markers as well as the absence of staining for S100 protein. To assess better the spectrum of histopathological and immunohistochemical features of JXG, we studied nine cases of classic or histologic variant of JXG. The cases were evaluated by light microscopy and with an extensive battery of antibodies. All 9 cases, regardless of their light microscopic appearance, showed markedly positive staining with histiocytic markers including CD68, HAM56, cathepsin B and vimentin, but did not stain for S100 protein. Antibodies to factor XIIIa stained positively in 8 cases while staining for other markers was variable. Our results suggest that the histiocytes in JXG lesions have macrophagic differentiation, probably representing a reactive process to an unknown stimulus.

Background: Merkel cell carcinoma (MCC) is a cutaneous neoplasm, histopathologically difficult to differentiate from other small blue cell neoplasms. Immunohistochemical and ultrastructural analyses are usually helpful in differentiating these neoplasms. Recently, cytogenetic analysis has emerged as a potential tool in the diagnosis of solid neoplasms, including MCC., Objective: To describe the immunohistochemical and cytogenetic features of a case of primary MCC and to review the cytogenetics literature on MCC., Methods: Formalin-fixed tissue was processed routinely and labeled with a battery of antibodies. Metaphase cells from fresh tissue were prepared by Giemsa banding., Results: Histopathologically, there were irregular aggregates of pyknotic cells with little cytoplasm. Immunohistochemically, the neoplastic cells stained positive for neurofilament, cytokeratin, neuron-specific enolase, and epithelial membrane antigen. Leucocyte common antigen, S-100, 013, and chromogranin were negative. Karyotyping of neoplastic cells showed loss of chromosome Y (-Y)., Conclusions: Coexpression of cytokeratin and neurofilament is characteristic of MCC and allows it to be differentiated from similar neoplasms. The significance of Y chromosome loss is unclear. Further cytogenetic analyses are warranted to identify genetic mutations significant to the pathogenesis of MCC.

Primitive neuroectodermal tumors are rare, highly aggressive neoplasms that affect both sexes and occur in all age groups. They are a large group of neoplasms with neuroepithelial differentiation, including cutaneous neuroblastomas. Histopathologically they are characterized by a rather uniform population of small, dark cells, with or without Homer Wright rosettes. Immunohistochemically they stain for one or more of the reputed neural markers. Ultrastructurally they show interdigitating processes containing neurosecretory granules, intermediate filaments, and microtubules. We describe a patient with unusual multiple peripheral neuroectodermal tumors localized to the skin, with benign biologic behavior. The patient related the appearance of new lesions for several years without evidence of visceral dissemination or systemic complications. The histopathologic, immunohistochemical, and ultrastructural findings support the diagnosis of a peripheral neuroectodermal tumor.

A dermal ductal tumor developed in sweat gland in 82 years old man, is presented. The lesion was located in the left leg. The clinical diagnosis was verrucous carcinoma and pigmented nevus. Histologically, it was a benign tumor.

He was a patient with 3,065 lesions of different sizes on the skin, placed in arms, legs, sternum area and right thorax, since he was 22 years old. The leiomyomas were painful and with electrical sensation, when you touch them. Faint. He denied similar lesions in relatives. We found abnormal brain vessels and bone tumor in right petrous bone.

We present a case of clear cell acanthoma localized on inferior third of the external portion of the left leg, the evolution was of one and a half year, with previous insect bites on the area. We insist on the histologic appearance, characterized by hyperplasia of epithelial cells, intercellular bridges, and presence of acidophilic hyalins intracytoplasmiques. Nous postulons la possibility of a viral etiology, transmitted by insect bite, of an epidermotropal virus.