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Background: Microsatellite instability (MSI) has prognostic value and impacts therapy strategies in several malignancies. Data regarding MSI in melanoma are scarce. The aim of this study was to assess MSI through the analysis of MMR protein expression in patients with melanoma., Methods: An observational retrospective single-center study was designed based on patients with primary melanoma. We assessed MSI through immunohistochemical staining with anti-MLH1, anti-MSH2, anti-MSH6, and anti-PMS2 on full-thickness excision tissue., Results: Ninety-three patients were included in this study. The complete absence of nuclear staining in tumoral cells was extremely rare, with only one melanoma not expressing MSH6. Most melanomas showed an expression index for MLH1 (77.7%), MSH2 (87.2%), and PMS2 (78.6%) ≥ 75%. Most melanomas (57.8%) exhibited an MSH6 expression index in the range of 1%-74%. A low MSH6 expression index and a reduced combined MMR protein expression index (MMR-e) were significantly associated with higher melanoma-specific survival. A mild PMS2 staining intensity was significantly associated with a higher melanoma-specific survival. The patients with high MMR-e who received immunotherapy progressed and died more frequently than those with reduced MMR-e (75% vs. 33.3%)., Conclusion: More studies are needed to further define the role of MSI in melanoma prognosis and response to immunotherapy., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

We report on a child with a divided or kissing nevus of the penis with benign symmetric globular pattern on dermoscopic examination that evolved into a globular-reticular pattern after 1 year of follow-up. Divided nevus of the penis is exceedingly rare, with only four cases with dermoscopic findings reported to date. Dermoscopy seems to be useful when deciding on the most appropriate management of these cases., (© 2018 Wiley Periodicals, Inc.)

Spitz nevus is a benign melanocytic proliferation that shows relatively characteristic clinicopathologic features. Despite this, Spitz nevus is clinically confused with many other lesions, and histopathologically it is sometimes difficult to distinguish it from melanoma. However, Spitz nevus rarely causes differential diagnostic problems with granulomatous dermatitis. This article describes an 8-year-old girl who presented with a nodule on her right arm, a clinical appearance of a pyogenic granuloma. Histopathologically, there was a dermal lesion composed of aggregates of large epithelioid cells surrounded by a heavy inflammatory infiltrate, mimicking a sarcoid-like granulomatous dermatitis. Immunohistochemistry showed epithelioid cells with strong nuclear and cytoplasmic staining with S-100 protein, thus establishing the diagnosis of a melanocytic tumor. The heavy T-cell lymphocytic infiltrate that accompanies the large epithelioid cells caused its granulomatous appearance. Molecular assessment showed H27H mutation in the HRAS gene. We suggest the term 'pseudogranulomatous' for this variant of Spitz nevus because it indicates that the lesion is not authentically granulomatous and simply mimics a granulomatous dermatitis., (Copyright © 2012 John Wiley & Sons A/S.)

Background: Mycosis fungoides (MF) is the most common type of cutaneous T-cell lymphoma. In early stages of the disease many different clinicopathologic variants have been observed. Currently, a papular variant of MF which is characterized by a good prognosis has been described., Objective and Methods: Because only seven cases have been reported in the literature, clinical and morphological data of this variant are not well established. We report the clinical and histopathological characteristics of two new patients with papular mycosis fungoides and review the previous cases reported in the literature., Results: The two cases of this early variant of MF were characterized by the presence of papules which, unlike the papules of lymphomatoid papulosis, did not show a tendency for spontaneous resolution. Histologic examination confirmed the diagnosis of MF in all cases. Immunohistochemical staining for CD30 was negative in all two cases. Follow-up data of our two patients confirmed the non-aggressive behavior of the disease, confirming that the lesions were not manifestations of advanced MF., Conclusion: Papular MF is a new variant of early MF characterized by a good prognosis in the long term follow- up. Thus, it should be added to the long list of clinicopathologic subtypes of MF.

Reed nevus, also named pigmented spindle cell nevus, is a peculiar melanocytic nevus, now regarded as a variant of Spitz nevus by the majority of authors. It is characterized by spindle-shaped melanocytes disposed in nests located in epidermis and papillary dermis. It is usually heavily pigmented, and many melanophages may also be present. Hypopigmented Reed nevus shows all the typical features of conventional pigmented spindle cell nevus, but it does not contain abundant melanin. This variant of Reed nevus is poorly described in literature, so we report five cases of hypopigmented Reed nevus and discuss its clinical and histopathological features., (Copyright Blackwell Munksgaard 2008.)

Peripheral T-cell lymphomas are uncommon, accounting for only 10% to 15% of all non-Hodgkin lymphomas and their classification has been controversial. We report a case of peripheral T-cell lymphoma with angiocentric growth pattern which presented as a paratesticular tumoral nodule in a 47-year-old-man. Formalin-fixed paraffin-embedded samples from the paratesticular tumor and non-infiltrated adjacent tissue were submitted to histological, immunohistochemical, polymerase chain reaction (PCR)-based and in situ hybridization analysis. Histopathologically, there was a lymphomatous infiltrate in the paratesticular soft tissue, composed of a variable mixture of medium-sized to large cells with large cytoplasm and irregular-shaped nuclei, together with blood vessel destruction, necrosis and karyorrhexis. Immunohistochemical study revealed a high p53 expression in neoplastic cells that showed T cytotoxic immunophenotype, failing to express the natural killer (NK)-cell antigen CD56. A monoclonal rearrangement of the T-cell receptor (TCR) gamma gene by a PCR technique was demonstrated. Type-A Epstein-Barr Virus (EBV) DNA was detected by PCR-based analysis. A combined in situ hybridization and immunohistochemical study revealed that most cells labeled positive for EBV RNA showed immunostaining with the CD45RO antibody. Based on the above results, the case reported was classified as extranodal peripheral T-cell lymphoma with cytotoxic phenotype and EBV associated. The present case does not fit neatly into any of the specific types of peripheral T-cell lymphomas of the REAL classification, so a diagnosis of peripheral T-cell lymphoma unspecified was made.

The appearance of pigmented lesions in melanoma surgical scars is a frequent finding that in some instances may cause confusion with a melanoma persistence. Nevertheless, only a few papers have dealt with this subject in the dermatologic literature. The melanoma surgical scars of 60 consecutive patients were reviewed with special attention to the presence of pigmentation and its clinical characteristics. Simultaneously, the scars of 60 consecutive patients who had been subjected to excision of a non-melanoma skin tumor were also studied. Biopsies were performed in representative clinical cases of pigmented lesions arising on the scars of both groups, as well as in non-pigmented scars, and processed for hematoxylin-eosin and immunohistochemistry. Pigmented lesions were present in a similar percentage in both groups (30% in melanoma scars (18/60) and 25% in non-melanoma scars (15/60)). Clinically, three types of clinical pigmentation were observed: lentigine-like lesions; pigmented streaks in scars after direct closure; and diffuse pigmentation in grafts. Histologically, two patterns emerged: one with lentiginous epidermal hyperplasia, hyperpigmentation, and a normal or moderately increased number of melanocytes; and a second one characterized by melanocytic hyperplasia of a variable degree. The scar process itself, irrespective of the tumor excised, seems to be responsible for the pigmentation. We suggest the existence of an induction process of scar tissue acting on melanocytes of the overlying epidermis.

An 18-year-old girl had a progressive enlarging plate of subcutaneous bone in the scalp since birth. Histologic examination of the lesion showed typical osteoma cutis. There was no history of any skin disease prior to development of the osteoma. Frequently congenital and usually located on the scalp, platelike osteoma is a rare variant of osteoma cutis.