Utility of T-cell immunosequencing in distinguishing mycosis fungoides progression from treatment related cutaneous adverse events

Novel and recurrent histopathologic patterns of mogamulizumab-associated rash: diagnostic implications and insights for accurate diagnosis

BACKGROUND

Mogamulizumab-associated rash (MAR) is a frequent side-effect of a treatment with Mogamulizumab that poses diagnostic challenges.

PATIENTS AND METHODS

We reviewed our database for novel histological patterns in MAR.

RESULTS

Four new histological patterns were identified: (1) A pagetoid pattern, which could be mistaken for CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma. (2) A lupus erythematosus-like pattern, characterized vacuolar interface dermatitis, deep perivascular lymphocytic infiltrate, interstitial mucin deposits, and clusters of CD123+ plasmacytoid dendritic cells. (3) Pustular folliculitis/acneiform pattern, which may clinically and histologically resemble acne. (4) A combined pattern with MAR coexisting with residual or new infiltrates of the original/underlying lymphoma. Previously described main patterns were reproducible. The folliculotropic and MF-like epidermotropic infiltrate should be also mentioned as separate patterns. Immunohistochemistry and the comparison with the original lymphoma remain crucial for diagnosis, especially a shift towards CD8+ cells, CD7 expression by infiltrating lymphocytes, and an increased number of histiocytes across all MAR patterns.

CONCLUSIONS

MAR presents a range of histological patterns that mimic other conditions, underscoring the importance of careful histopathological and immunohistochemical analysis and clinicopathological correlation for accurate diagnosis and management.

[Clues in dermatopathological diagnostics]

Numerous diagnostic clues are used in routine dermatopathological diagnostics. Ideally, a diagnostic clue can lead directly to a specific diagnosis and save further time-consuming additional diagnostic procedures. This article discusses the concept of "clues to diagnosis" starting from its historical beginnings with a review of relevant studies and including current literature. Selected clues to dermatophytosis, psoriasis, and mycosis fungoides are analyzed. In addition, some newer and still little-known dermatopathological clues to inflammatory and infectious skin disease are presented. The aim is to specify the use of clues on the basis of current findings and to draw attention to scientifically sound clues.

Immunosequencing applications in cutaneous T-cell lymphoma

Immunosequencing has emerged as a newer clinical test for assessment of T-cell clonality in the blood and skin of cutaneous T-cell lymphoma (CTCL) patients. Utilization of immunosequencing, also known as high-throughput sequencing of the T-cell receptor (HTS-TCR), enables identification and quantification of the precise genetic signature of dominant T-cell clones. Although immunosequencing is more sensitive than commonly used methods such as polymerase chain reaction (PCR) paired with capillary electrophoresis or flow cytometry, it remains underutilized for CTCL management. Nonetheless, incorporation of HTS-TCR in clinical practice offers distinct advantages compared to other molecular analyses that may improve diagnostic evaluation, prognostication, and disease monitoring in CTCL. The objective of this comprehensive review is to provide a thorough explanation of the application of immunosequencing in the context of CTCL. We describe the significance of T-cell clonality and the methods used to detect it, including a detailed comparison between PCR paired with capillary electrophoresis and HTS-TCR. The utilization of immunosequencing in the blood and skin of CTCL patients is discussed in depth, specifically outlining how HTS-TCR can assist in diagnosing CTCL, predicting outcomes, and tracking disease progression. Finally, we address the potential applications of immunosequencing in clinical management and research as well as the novel challenges it presents.