Dermatology: Practical and Conceptual Research Letter | Dermatol Pract Concept. 2024;14(2):e2024084 1 Dermoscopic Presentation of Two Cases of Pigmented Purpuric Dermatosis-like Mycosis Fungoides Neil Vaishampayan1, Andrew Schuler2, Anne Ning2, Alexandra Hristov2, Douglas Fullen2, Trilokraj Tejasvi2 1 University of Michigan Medical School, Ann Arbor, Michigan, USA 2 Department of Dermatology, University of Michigan, Ann Arbor, Michigan, USA Key words: dermoscopy, purpuric mycosis fungoides, PPD Citation: Vaishampayan N, Schuler A, Ning A, et al. Dermoscopic Presentation of Two Cases of Pigmented Purpuric Dermatosis-like Mycosis Fungoides. Dermatol Pract Concept. 2024;14(2):e2024084. DOI: https://doi.org/10.5826/dpc.1402a84 Accepted: October 21, 2023; Published: April 2024 Copyright: ©2024 Vaishampayan et al. This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing Interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding Author: Trilokraj Tejasvi, MD, Department of Dermatology, University of Michigan, 1910 Taubman Center, 1500 E. Medical Center Drive, Ann Arbor, MI 48109. E-mail: ttejasvi@med.umich.edu  Introduction Purpuric mycosis fungoides (PMF) is an extremely rare subtype of cutaneous T-cell lymphoma. The diagnosis of PMF is often challenging as its clinical presentation and der- moscopy findings closely resemble pigmented purpuric der- matosis (PPD) [1]. Given the low incidence of PMF, there is a paucity of literature concerning the dermoscopic findings of this entity. A case series by Nasimi et al. compared the dermoscopy features of 28 cases of PMF and 13 cases of PPD. The presence of spermatozoa-like structures and fine short linear vessels were found to be statistically significant distinguishing features of PMF on dermoscopy [1]. Addi- tionally, dermoscopy findings of erythematous clods on a coppery background and reticular pigmentation were signifi- cantly associated with PPD compared to PMF [1-3]. Here, we showcase two cases of histopathology-confirmed PMF that did not display the specific dermoscopy features of PMF previously described in the literature. Instead, our dermos- copy findings more closely resembled classic findings seen in benign PPD, representing a potential diagnostic pitfall. Case Presentation Case 1. An otherwise healthy 13-year-old presented with a 5-year history of stable asymptomatic red-brown patches affecting the groin, buttocks, thighs, and upper inner arms. Clinical examination revealed cayenne-pepper-colored patches and macules. Dermoscopy displayed dotted and clustered vessel morphology and distribution, no scales, no follicular findings, erythematous clods with inter- spersed brown dots, and admixed brown reticular lines on a coppery-brown background [4]. Histopathology revealed 2 Research Letter | Dermatol Pract Concept. 2024;14(2):e2024084 an atypical CD3+/CD8+ lymphoid infiltrate showing epi- dermotropism loss of CD7 and diminished CD5. Erythema- tous clods, seen on dermoscopy, corresponded to numerous extravasated erythrocytes. T-cell clonality studies demon- strated a clonal T-cell population. This constellation of find- ings indicated PMF. Case 2. A 65-year-old female with history of a B-cell lymphoproliferative disorder and biopsy-confirmed mycosis fungoides on her left abdomen presented with pruritic flare of a poorly demarcated erythematous rash with cayenne-pepper macules, notably on her left calf. Dermos- copy showed dotted vessel morphology, no scales, no follic- ular findings, and red clods with interspersed brown dots on a coppery-brown background [4]. Histopathology revealed a CD4-positive, epidermotropic T-cell infiltrate with loss of CD7 and extravasation of erythrocytes. T-cell clonality studies showed a clonal T-cell population with base pair peaks identical to the abdomen. The patient was diagnosed with PMF. Conclusion The dermoscopic findings in these cases of PMF are distinct from findings in the literature. Notably, our cases lacked spermatozoa-like structures and fine short linear vessels, which have been associated with conventional mycosis fungoides (MF) as well as with PMF [1, 5]. The dermoscopic findings in our cases were more in keeping with conventional PPD [5]. Furthermore, there is a wide spectrum of dermoscopic features associated with mycosis fungoides ranging from linear vessels and white scales to the red-brown globules, no scales, and brown reticular lines described in these cases. Indeed, the wide range of reported dermoscopic features within MF render diag- nosis based on dermoscopy alone challenging [6]. Further study is needed to adequately describe the dermoscopic features of PMF and differentiate it from potential mimickers. In lieu of reliable dermoscopic features in PMF, it is imperative that the clinician integrates clinical, dermoscopic, and ancillary studies and histologic features for correct diagnosis. Figure 1. PMF (Case 1): A) Clinical: 13-year-old with cayenne-pepper-colored patches and macules on thighs and groin. B) Dermoscopy: erythematous globules, interspersed brown dots, admixed brown reticular lines on a coppery-brown background. C) Histopathology: Epidermotropic and band-like lymphocytes with numerous extravasated erythrocytes. Research Letter | Dermatol Pract Concept. 2024;14(2):e2024084 3 Table 1. Existing dermoscopy findings of PMF and PPD in the literature compared to our two reported cases [1, 2, 5]. PMF PPD Two reported cases of PMF Spermatozoa-like vascular morphologic structures Erythematous globules Erythematous clods with interspersed brown dots Fine short linear vessels Reticular pigmentation Admixed brown reticular pigmentation lines Orange-yellow background Dull red-brown background Coppery-brown background Distributed dotted vascular morphology Distributed dotted vascular morphology Dotted vascular morphology Clustered vascular distribution Clustered vascular distribution Clustered vascular distribution No scales No scales No scales In boldface: Features described as statistically significant for the condition in the existing literature. Figure 2. PMF (Case 2): A) Clinical: 65-year-old with a poorly demarcated erythematous rash with cayenne-pepper macules on left calf. B) Dermoscopy: erythematous globules interspersed with brown dots on a coppery-brown background. C) Histopathology: Epidermotropic lymphocytes with extravasated erythrocytes. 4 Research Letter | Dermatol Pract Concept. 2024;14(2):e2024084 4. Errichetti E, Zalaudek I, Kittler H, et al. Standardization of dermoscopic terminology and basic dermoscopic parameters to evaluate in general dermatology (non-neoplastic dermatoses): an expert consensus on behalf of the International Dermoscopy Society. Br J Dermatol. 2020 Feb;182(2):454-467. doi: 10.1111 /bjd.18125. Epub 2019 Jul 28. PMID: 31077336. 5. Metin MS, Elmas ÖF. Dermoscopic profile of pigmented pur- puric dermatosis: new observations. Postepy Dermatol Alergol. 2019 Dec;36(6):687-691. doi: 10.5114/ada.2019.91419. Epub 2019 Dec 30. PMID: 31997996; PMCID: PMC6986287. 6. Errichetti E, Apalla Z, Geller S, et al. Dermoscopic spectrum of mycosis fungoides: a retrospective observational study by the In- ternational Dermoscopy Society. J Eur Acad Dermatol Venereol. 2022 Jul;36(7):1045-1053. doi: 10.1111/jdv.18078. Epub 2022 Mar 28. 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