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Interactive Case Study - October 2025

85-year-old man with purpuric macules and papules at the abdomen, hips, and bilateral lower legs
Phuoc Christie-Nguyen, MD 
Thuy Phung, MD, PhD 
Xiaohong Iris Wang, MD, PhD 
 
 
An 85-year-old male with a history of metastatic prostate cancer, diagnosed two years prior, previously treated with enzalutamide but not currently receiving therapy, presented with decreased appetite, altered mental status, and increased somnolence. His disease course includes spinal metastases with associated cord compression. Physical examination revealed purpuric macules and papules scattering on the abdomen, hips, and bilateral lower legs.
Click here to view the virtual slide
Click here to view the virtual slide #2
Click here to view the virtual slide #3
Figure 1 - Bilateral legs with scattering purpuric macules and papules
Figure 1 - Bilateral legs with scattering purpuric macules and papules
Figure 2 - 40x
Figure 2 - 40x
Figure 3 - 100x
Figure 3 - 100x
Figure 4 - 400x
Figure 4 - 400x
Figure 5 – IHC stains
Figure 5 – IHC stains
Given that the IHC staining positive for CD4, CD43, CD68, CD56, and lysozyme, and negative for CD8, CD20, CD34, CD117, MPO, pancytokeratin, and CD123, which of the following is the best diagnosis?
Acute myeloid leukemia involving skin
Blastic plasmacytoid dendritic cell neoplasm
Ewing Sarcoma
Metastatic poorly differentiated carcinoma
Primary cutaneous diffuse large B-cell lymphoma, leg type
Which of the following statements regarding AML involving skin or myeloid sarcoma is correct?
AML involving skin is limited to patients with a known history of AML
Myeloid sarcoma requires ≥20% blasts to establish the diagnosis
NPM1 is the most commonly mutated gene in cutaneous myeloid sarcoma with associated monocytic differentiation
Patients with isolated myeloid sarcoma or AML involving skin have a worse prognosis than those with concomitant bone marrow involvement
The skin is an uncommon site for myeloid sarcoma
  1. Kaur V, Swami A, Alapat D, Abdallah AO, Motwani P, Hutchins LF, et al. Clinical characteristics, molecular profile and outcomes of myeloid sarcoma: a single institution experience over 13 years. Hematology. 2018 Jan;23(1):17–24. 

  2. Chen W, Medeiros LJ, Venkataraman G, Battistella M. Cutaneous involvement in myeloid neoplasms, including myeloid sarcoma. In: WHO Classification of Tumours Editorial Board. Skin tumours. Lyon (France): International Agency for Research on Cancer; forthcoming. [Internet]. 5th ed. (WHO classification of tumours series; vol. 12). Available from: https://publications.iarc.fr.

  3. Demiröz AS, Demirkesen C, Salihoğlu A, Tüzüner N. Blastic Plasmacytoid Dendritic Cell Neoplasia: A Single Center Experience. Turk J Haematol. 2020 Mar;37(1):48–52. 

  4. Grassetti L, Torresetti M, Brancorsini D, Rubini C, Lazzeri D, Di Benedetto G. A peculiar case of large primary cutaneous Ewing’s sarcoma of the foot: Case report and review of the literature. International Journal of Surgery Case Reports. 2015 Jan 1;15:89–92. 

  5. Dills A, Obi O, Bustos K, Jiang J, Gupta S. Cutaneous Metastasis of Prostate Adenocarcinoma: A Rare Presentation of a Common Disease. J Investig Med High Impact Case Rep. 2021 Feb 17;9:2324709621990769. 

  6. Gros A, Menguy S, Bobée V, Ducharme O, Cassaigne IC, Vergier B, et al. Integrative diagnosis of primary cutaneous large B-cell lymphomas supports the relevance of cell of origin profiling. PLoS One. 2022;17(4):e0266978. 

  7. Hurley MY, Ghahramani GK, Frisch S, Armbrecht ES, Lind AC, Nguyen TT, et al. Cutaneous Myeloid Sarcoma: Natural History and Biology of an Uncommon Manifestation of Acute Myeloid Leukemia. Acta Dermato-Venereologica. 2013;93(3):319–24. 

  8. Luskin MR, Huen AO, Brooks SA, Stewart C, Watt CD, Morrissette JJD, et al. NPM1 mutation is associated with leukemia cutis in acute myeloid leukemia with monocytic features. Haematologica. 2015 Oct;100(10):e412-414. 

  9. Movassaghian M, Brunner AM, Blonquist TM, Sadrzadeh H, Bhatia A, Perry AM, et al. Presentation and outcomes among patients with isolated myeloid sarcoma: a Surveillance, Epidemiology, and End Results database analysis. Leuk Lymphoma. 2015 Jun;56(6):1698–703. 

  10. Pileri SA, Ascani S, Cox MC, Campidelli C, Bacci F, Piccioli M, et al. Myeloid sarcoma: clinico-pathologic, phenotypic and cytogenetic analysis of 92 adult patients. Leukemia. 2007 Feb;21(2):340–50.

 

Acknowledgements

 

Author Profiles

Phuoc Christie-Nguyen, MD

University of Texas Health Science Center

Phuoc Christie-Nguyen, MD, is a dedicated pathology resident at The University of Texas Health Science Center at Houston. His work emphasizes dermatopathology and cutaneous malignancies, driven by personal and professional passion. Dr. Christie-Nguyen is recognized for his scholarly contributions, including case reports and publications, and was recently honored with the Texas Society of Pathologists Education Foundation Scholarship. His commitment to excellence is reflected in his leadership, research, and dedication to advancing pathology.

 

Thuy Phung, MD, PhD

University of Texas Health Science Center

Thuy Phung, MD, PhD is professor and medical director of molecular pathology at the University of Texas Health Science Center at San Antonio. She is spearheading efforts to enhance molecular diagnostics for cancer patients in South Texas. She is the lead author of Pediatric Dermatopathology, a comprehensive textbook in the field. Dr. Phung pursues translational research in vascular anomalies in children, with a focus on identifying key molecular pathways that drive the development and growth of these lesions and developing new therapy targeting these pathways. In addition to her clinical and scientific work, Dr. Phung is passionate about global health. She is a co-founder of the award-winning Vascular Anomalies Center in Ho Chi Minh City, Vietnam, which cares for thousands of underserved children with vascular anomalies. Dr. Phung also leads a program in global pathology to enhance the standards of dermatopathology practice in Vietnam.

 

Xiaohong Iris Wang, MD, PhD

I am currently an associate professor working at both university and community hospital. With many years of basic research background and advanced training, I am actively involved in research of tumor microenvironment. By practicing both hematopathology and surgical pathology, I am with broad knowledge in the field. In last 5 years, I am a coauthor of 14 peer reviewed papers. I also published many abstracts with trainees and visiting scholars.

 

 

 

 

 

 

 

Question:

 

 

 

 
 

85-year-old man with purpuric macules and papules at the abdomen, hips, and bilateral lower legs

Category

Tumors > Lymphomatous/Leukemic Infiltrates

Description

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