Sir,

B-cell lymphoma is an indolent lymphoma that presents with fluctuating asymptomatic lymphadenopathies. It is crucial to differentiate secondary cutaneous localization of systemic B-cell lymphoma from primary cutaneous B-cell lymphoma. Immunophenotypic analysis and extent assessment aid in making this distinction [1]. Herein, we present a case of secondary cutaneous localization of nodal B-cell lymphoma with a distinctive feature of lesion distribution in the folds and adnexal structures, as well as the evolution of the lesions before the discovery of systemic lymphoma.

The patient was a fifty-year-old male who had been under observation for confirmed nodal B-cell lymphoma for three months and was referred to us for dermatological evaluation due to pruritic cutaneous lesions evolving for over three years. Dermatological examination revealed the presence of erythematous and squamous plaques in the inguinal and axillary folds (Fig. 1c), as well as on the face and neck, with areas of eczematization (Fig. 1a). An examination of the adnexal structures revealed periungual (Fig. 1b) and palmoplantar hyperkeratosis, erythematous squamous scalp plaques, and a positive traction sign. Skin and scalp dermoscopy revealed punctate vascularization without a specific pattern. Given this appearance, considerations included mycosis fungoides, Bazex syndrome, and secondary lymphoma localization. After treating eczematization, a skin biopsy was performed, revealing the presence of suspicious cells expressing CD79a, CD30, Bcl6, and Mum1, indicating secondary cutaneous localization of systemic B-cell lymphoma (Figs. 2a – 2e). The patient underwent chemotherapy (rituximab, etoposide, cyclophosphamide, doxorubicin, vincristine, Medrol), and the lesions completely disappeared during treatment (Figs. 3a – 3c).

	Figure 1: Clinical image showing the presence of erythematous scaly plaques with excoriated surfaces on the scalp (a), periungual (b), and on the inner thigh (c).
	Figure 2: Histological image: Scattered large cells (black arrows) within a subepidermal and perivascular lymphocytic inflammatory infiltrate (a: HES 40x, b: HES 100x, c: HES 200x) and positive staining for CD79a (d) and CD30 (e).
	Figure 3: (a-c) Clinical image showing the complete disappearance of the lesions after treatment.

Cutaneous involvement in systemic lymphoma remains relatively rare, with limited data available on its typical clinical description [2]. Often, lesions are papulonodular and located on the trunk for B-cell lymphomas and on the head for T-cell lineages. Cutaneous involvement serves as a poor prognostic factor, especially when it appears within six months following systemic lymphoma diagnosis [2,3]. The uniqueness of our patient lay in the atypical clinical presentation concerning the site of lesions and their duration of progression before diagnosing nodal B-cell lymphoma, as well as the presence of palmoplantar hyperkeratosis and scalp involvement. Histology confirmed the diagnosis, and the positivity of Bcl2 guided us toward a secondary origin. Thus, the skin may be a site of invasion for various systemic lymphomas, including B-cell lymphoma. This possibility should be considered when there is involvement of the adnexal structures associated with the folds and face. Positivity of Bcl2 in histology points toward this secondary origin [4].

REFERENCES

1.  Sahil M, Prins C, Kaya G, Poffet F, Boehncke WH, Cortés B. Atypical presentation of centrofollicular B cell lymphoma. Rev Med Suisse. 2014;10:744-8.

2.  Lee WJ, Won KH, Won CH, Chang SE, Choi JH, Moon KC, et al. Secondary cutaneous lymphoma:Comparative clinical features and survival outcome analysis of 106 cases according to lymphoma cell lineage. Br J Dermatol. 2015;173:134-45.

3.  Rickaby RW, Calonje E. Cutaneous involvement from systemic lymphoma. Br J Dermatol. 2015:12-3.

4.  Bagot M. Les lymphomes cutanés. Springer. 2013.