A rare case of mycosis fungoides with porokeratosis-like lesions: a case report and review of previous literature

Introduction

Cutaneous T-cell lymphomas (CTCLs) are the second most prevalent group of extranodal lymphomas second to B-cell lymphomas (1). Among them, mycosis fungoides (MF) stands as the most frequently diagnosed cutaneous lymphoma and it represents a neoplasia of malignant monoclonal T lymphocytes that primarily invade the skin, leading to various cutaneous manifestations. These manifestations can range from erythematous scaly patches and plaques in the early stages to tumors or erythroderma in advanced stages, often with lymph nodes or visceral involvement (2,3). MF is also characterized by its diverse clinical manifestations, which may include hypopigmented, hyperpigmented, hyperkeratotic, pigmented-purpuric, verrucous, and pityriasis lichenoides-like lesions (4-9). Histologically, MF presents as an epidermotropic infiltrate of small to medium-sized CD4⁺ T lymphocytes with cerebriform nuclei. The classic immunophenotype of MF is CD3⁺/CD4⁺/CD45RO⁺ memory T cells (2,3). The diagnosis of CTCL is frequently postponed due to its ability to resemble both common and uncommon dermatological conditions (1). The occurrence of MF with features resembling porokeratosis is notably rare, with only four instances documented in the medical literature (10-12). This report introduces a rare case involving a 44-year-old male diagnosed with MF, who exhibited lesions akin to porokeratosis. We present this case in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-24-210/rc).

Case presentation

A 44-year-old male presented at the outpatient clinic with a seven-month history of lesions on both feet. Initially, the lesions appeared suddenly as a few skin-colored spots, which subsequently increased in number, darkened, and developed a peripheral scale, although they were not itchy. The patient reported no similar lesions elsewhere on the body and denied any oral symptoms. He had no chronic illnesses in his medical history and no family history of similar conditions, and has never been treated previously for a similar condition. Upon examination, multiple brownish papules with a collarette of scale, clinically resembling porokeratosis, were observed symmetrically distributed over the medial and lateral aspects of the dorsum of both feet, with additional similar lesions on the plantar aspects (Figure 1). A skin biopsy from the foot was obtained and revealed an acanthotic epidermis with a band-like infiltrate of lymphocytes in the papillary dermis and some papillary dermal fibrosis (Figure 2). Many lymphocytes within the epidermis exhibited a perinuclear halo; others showed mild nuclear enlargement and hyperchromasia (Figure 3). Immunohistochemical analysis showed diffuse positivity for CD3 and CD8 in both the epidermis and dermis. CD4 was mainly positive in dermal lymphocytes, while CD7 was predominantly absent in the epidermal lymphocytes (Figure 4). CD30 was negative. Although histology does not exhibit a cornoid lamella, the clinicopathologic correlation and immunohistochemistry confirmed the diagnosis of porokeratosis-like MF. The patient was prescribed daily applications of Clobetasol propionate 0.05% ointment and scheduled for follow-up (biweekly for 3 months). Two weeks after initiating the treatment plan, the patient reports adherence to topical therapy and improving skin lesions (partial improvement). The patient reports absence of recurrence during this period, with no associated adverse effects to therapy. No changes in treatment plan were done. Case timeline of events are provided in (Figure 5). All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Figure 1 Clinical presentation of porokeratosis-like lesions. (A) Multiple scattered brownish papules, some with a collarette of scale over the lateral aspect of the left ankle. (B) Few scattered brownish papules, some with a collarette of scale over the medial aspect of the right foot.

Figure 2 Photomicrographs of the skin punch biopsy reveal an acanthotic epidermis with a band-like infiltrate of lymphocytes in the papillary dermis, with papillary dermal fibrosis. (A) Hematoxylin and eosin stain, original magnification 10×. (B) Hematoxylin and eosin stain, original magnification 20×.

Figure 3 Many lymphocytes are present in the epidermis with perinuclear halo, some of the lymphocytes show mild nuclear enlargement and hyperchromasia. Hematoxylin and eosin stain, original magnification 400×.

Figure 4 Immunohistochemistry reveals loss of CD7 in most of the epidermal lymphocytes and highlights some of the dermal lymphocytes. Immunohistochemistry stain, original magnification 200×.

Figure 5 Case timeline of events.

Discussion

This case contributes to the rare but expanding body of knowledge on porokeratosis-like MF. MF is the most prevalent type of CTCL. It commonly affects older adults, exhibiting a male-to-female incidence ratio of approximately (1.6–2.0:1), although it can also occur in children and adolescents. Clinically, MF presents as an indolent eruption of erythematous scaly patches or plaques, which can resemble common dermatological conditions such as atopic dermatitis or psoriasis. Initially, lesions typically manifest in sun-protected areas, but they can eventually involve any skin site (13). A myriad of clinical variants of MF have been documented. Histopathologically, MF is characterized by variable features, commonly including a superficial band-like lymphocytic infiltrate and atypical lymphocytes exhibiting epidermotropism (14). These epidermal lymphocytes often appear larger and more atypical than those in the dermis and are frequently surrounded by a halo that delineates the lymphocyte nuclei from adjacent keratinocytes (15). In the dermis, papillary dermal fibrosis is typically observed (16). The findings in our case we presented align with these characteristics of MF. The immunophenotype of MF generally features epidermotropic peripheral T lymphocytes, typically expressing CD2⁺, CD3⁺, CD4⁺, CD5⁺, CD8⁻, CD45RO⁺, CD20⁻, and CD30⁻. Occurrences of CD4⁻ or CD8⁺, double positive or double negative cases are infrequent (17,18). A loss of CD7 expression is often noted even in the early stages of the disease (18). The biopsy from our patient corresponded with this expected immunophenotype of MF, exhibiting CD7 loss and double positivity for CD4 and CD8.

MF presenting with porokeratosis-like lesions have been seldom reported. The first two cases were described by Hsu et al. in 1992, involving two black patients with widespread, sharply demarcated, round hyperpigmented or hypopigmented macules that clinically resembled disseminated superficial actinic porokeratosis (10). In 1993, Breneman et al. reported a case of MF that mimicked porokeratosis of Mibelli (11). The most recent case was documented by Tawfiq et al. in 2014, involving a young male with generalized hyperpigmented macules similar to porokeratosis of Mibelli (12). Previous cases of porokeratosis-like MF, such as those reported by Hsu et al. and Breneman et al., had different lesion distributions and were not limited to the feet. This case differs by its localized foot involvement. The patient’s lesions, confined to the feet, represent an uncommon distribution for such MF variants.

Our patient presented with localized lesions on both feet, appearing as multiple scattered brownish papules, some with a collarette of scale, and including plantar involvement. The clinical differential diagnosis considered porokeratosis, secondary syphilis, and MF. Given the unusual presentation, a clinicopathologic correlation was essential to establish the diagnosis. The importance of recognizing such rare clinical variants lies in the implications for management and prognosis. The ability to differentiate MF from other dermatoses that it may mimic, such as porokeratosis, is critical in avoiding misdiagnosis and ensuring appropriate treatment. Moreover, this case contributes to the broader dermatological knowledge by documenting an additional instance of MF mimicking porokeratosis, expanding the spectrum of known clinical presentations of this lymphoma. It emphasizes the need for heightened suspicion and comprehensive diagnostic strategies, particularly in cases where the clinical presentation deviates from the more typical manifestations of MF. By continuing to document and study such rare presentations, clinicians can enhance their understanding and improve outcomes for patients with this complex and variable disease. This case expands the limited spectrum of porokeratosis-like MF presentations. Limitations include the lack of long-term follow-up data on treatment efficacy, the absence of T-cell receptor rearrangement analysis (which is increasingly used in MF diagnosis), as well as lack of dermoscopic findings, which could have provided additional diagnostic clarity. We recommend including dermoscopy in future cases of porokeratosis-like MF to enhance diagnostic precision. Moreover, this unique variant may require tailored therapeutic strategies, emphasizing the need for further research into its specific management needs.

Conclusions

Porokeratosis-like MF is a rare and uncommon instance. The distinctive morphology and distribution of such lesions poses significant diagnostic challenges. It is imperative to include MF in the differential diagnosis when encountering atypical presentations of porokeratosis. A thorough clinicopathologic correlation is crucial for accurate diagnosis.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-24-210/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-24-210/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-24-210/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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