The interface reaction pattern in the skin: an integrated review of clinical and pathological features

Histopathology of autoimmune bullous dermatoses: What's new?

Autoimmune bullous dermatoses are characterized by the presence of tissue-bound and often circulating pathogenic autoantibodies targeting structural components of the skin and/or mucous membranes. The diagnostic workup for this heterogeneous group of disorders consists of a multi-step process, of which the light microscopic examination is a crucial component. This review is organized following a classification scheme that is based on two main histopathologic features, namely level of intraepithelial split and composition of the inflammatory infiltrate. Overall, we aim to place emphasis on the histopathologic clues that can assist pathologists in differential diagnosis and review the updates in the literature.

Red mark syndrome of trout (Oncorhynchus mykiss; Walbaum, 1792): Histopathological scoring and correlation with gross lesions

Red mark syndrome (RMS) is a skin disorder affecting rainbow trout (Oncorhynchus mykiss). The present work aimed to correlate the gross skin lesions affecting 46 fish sampled from farms surveyed for RMS with their microscopic features, identifying histological parameters that may be suggestive of disease progression. Skin lesions were grossly included in one of three categories (types I, II and III) according to the progressive degree of severity. Histological parameters and anti-proliferating cell nuclear antigen (PCNA) tissue immunoreactivity were semi-quantitatively assessed. In the dermis, PCNA-positive lymphocytes, fibroblasts and endothelial cells were indicative of active phlogosis. A significant increase in PCNA-immunoreactive lymphocytes, from gross type I to type III cases, was found only in the hypodermis. The histological parameters significantly associated with the gross lesion severity were progressive loss of the epithelium and scales, recruitment of inflammatory cells in the stratum compactum, loss of architecture of the stratum compactum, perivascular and perineural granulomatous inflammation and increase in lymphocyte infiltration of the muscular layer. In the type II and type III categories, inflammation in the hypodermis and muscle displayed a granulomatous pattern, reinforcing the hypothesis of an immunopathological mechanism. The morphological diagnosis of "deep chronic dermatitis associated to panniculitis and myositis, characterised by lympho-histiocytic and granulomatous reaction" is suggested.

Histopathologic Characterization of Mogamulizumab-associated Rash

Rash is one of the most common adverse events observed with mogamulizumab, an anti-C-C chemokine receptor 4 monoclonal antibody approved for previously treated mycosis fungoides (MF) and Sezary syndrome (SS). Given the nonspecific clinical presentations of this rash, histopathologic distinction from MF/SS is critical for informing clinical management. We performed a comprehensive characterization of the histopathologic findings in mogamulizumab-associated rash (MAR) with the integration of high-throughput sequencing of T-cell receptor (TCR) genes. Fifty-two biopsy specimens from 19 patients were evaluated retrospectively. Three major histologic reaction patterns were identified: spongiotic/psoriasiform dermatitis (33/52), interface dermatitis (11/52), and granulomatous dermatitis (8/52). Almost half of the specimens (21/52) showed at least 2 of these reaction patterns concurrently. Dermal eosinophils were not a consistent feature, being present in only half (27/52) of specimens and prominent in only 3. Features mimicking MF/SS, including lymphocyte exocytosis, lamellar fibroplasia, and adnexal involvement, were commonly seen but tended to be focal and mild. In 38/43 specimens with available immunohistochemistry, intraepidermal lymphocytes demonstrated a CD4:CD8 ratio ≤1 : 1. Low background levels of the patient's previously identified MF/SS-associated TCR sequence(s) were demonstrated in 20/46 specimens analyzed by high-throughput sequencing of TCR. We conclude that MAR may demonstrate diverse histologic features. Findings that may distinguish MAR from MF/SS include the inverted or normalized CD4:CD8 ratio within intraepidermal lymphocytes and demonstration of absent or nondominant levels of disease-associated TCR sequences. Correlation with the clinical findings and immunohistochemical and molecular characterization of the patient's MF/SS before mogamulizumab, when possible, may facilitate recognition of MAR.

Multimodal Imaging Mass Spectrometry: Next Generation Molecular Mapping in Biology and Medicine

Imaging mass spectrometry has become a mature molecular mapping technology that is used for molecular discovery in many medical and biological systems. While powerful by itself, imaging mass spectrometry can be complemented by the addition of other orthogonal, chemically informative imaging technologies to maximize the information gained from a single experiment and enable deeper understanding of biological processes. Within this review, we describe MALDI, SIMS, and DESI imaging mass spectrometric technologies and how these have been integrated with other analytical modalities such as microscopy, transcriptomics, spectroscopy, and electrochemistry in a field termed multimodal imaging. We explore the future of this field and discuss forthcoming developments that will bring new insights to help unravel the molecular complexities of biological systems, from single cells to functional tissue structures and organs.

[Pattern analysis of inflammatory skin diseases according to A. B. Ackerman-always up to date]

The exact microscopic diagnosis of inflammatory skin diseases requires the linking of histopathological findings with clinical features. This is not easy when skin biopsies are rarely assessed and the terminology of dermatopathology and dermatology is itself unfamiliar.The infiltrates of almost all inflammatory skin diseases tend to show eight specific patterns in high magnification. By further classifying according to architectural and cytological features, a specific diagnosis can be made in most cases. At the same time, clinically suspected diagnoses are simply excluded or greatly reduced in number. This procedure, starting with the overview magnification and the recognition of clearly defined histomorphological features, corresponds to an algorithm.Another algorithmic approach uses histomorphological changes under high magnification. Here, "nonspecific" findings are added to the pattern analysis as a diagnostic vehicle.Occasionally, inflammatory skin diseases cannot be assessed conclusively with current modern methods. Such pathology reports should be written descriptively and possible differential diagnoses should be mentioned as notes. The report should be written in a language understandable to the clinician.Artificial intelligence, with its ability to transform and integrate extensive clinical as well as image data, will play an important role in the future of decision making, diagnosing, and personalizing medicine. In the field of pathology, it could be seen as a second opinion. It is important that physicians always contribute their opinion where important algorithmic decisions are made, such as in algorithm design, data quality, interpretation, action, and feedback.

T-cell receptor antibodies expression in benign and malignant cutaneous lymphoid infiltrates in comparison with T-cell receptor gene rearrangement and its diagnostic utility in borderline cases

INTRODUCTION

Cutaneous T-cell lymphoid infiltrate can represent reactive lesion or a malignant T-cell lymphoma. However, clinical and histopathological appearance can overlap in both groups with a risk of misdiagnosis. Aberrant expression of T-cell markers is not always applicable and T-cell receptor (TCR) gene rearrangement is not always accessible and diagnosis in borderline cases can be challenging.

AIMS

Several types of TCR antibodies are currently available with limited knowledge of their expression in different cutaneous lymphoid infiltrates. Aim of the study is a comparison of expression of TCR antibodies in benign and malignant lymphoid infiltrates and their utility in borderline cases.

METHODS

Representative cases of reactive and malignant lymphoproliferations were collected. Separate group of lesions with borderline morphology was selected for comparison. Immunohistochemical expression of TCR-V-betaF1 (TCRBF1), TCR-C-beta1 (TCRJOVI.1), TCR gamma/delta (TCRGD) and TCR delta (TCRD) was performed in all cases. TCR gene rearrangement evaluation was performed in all cases using PCR BIOMED-2 assay.

RESULTS

Benign lymphoid infiltrates were all negative in TCRD and TCRGD. Expression of TCRJOVI.1 was seen in 3/10 cases and TCRBF1 in one. T-cell lymphomas were positive for TCRBF1 and TCRGD in 60% and 30% of cases respectively. TCR gene rearrangement was confirmed in 90% of lymphoma cases. All benign lesions were polyclonal. Morphologically borderline lesions showed expression of TCRBF1 in 6/10 cases and TCR gene rearrangement in 4/10 cases. Re-evaluation of the cases and clinical correlation led to the change of the diagnosis and confirmation of T-cell lymphoma in 4/10 cases.

CONCLUSIONS

Expression of TCRBF1 and TCR-gene rearrangement was significantly associated with malignant infiltrates. TCRBF1 positivity in borderline cutaneous lymphoproliferations can raise the suspicion of malignancy but confirmation by TCR gene rearrangement and careful clinical correlation is still advisable.