Mycosis Fungoides Associated with Pseudoepitheliomatous Hyperplasia.

Sir,

A 76-year-old Japanese woman was initially referred to us in 2003 for evaluation of a 4-year history of skin eruption. The eruption first appeared as generalized or widespread patches and plaques. She showed neither lymphadenopathy nor hepatosplenomegaly. A skin biopsy specimen from erythematous plaque disclosed numerous atypical lymphocytes in the dermis with their epidermotropism [Figure 1a]. The atypical cells were positive for CD3 and CD4 but negative for CD8, CD30, and CD56. Based on the immunohistochemical findings mentioned above, we diagnosed the skin lesions as mycosis fungoides. Initially, the patient was treated with a combination of intravenous IFN-γ and PUVA irradiation for the plaques that were present on her trunk and extremities. At the first-year follow-up, this therapy was effective with subsidence of lesions and she did not receive any therapy thereafter for 3 years. However, her skin lesions gradually reappeared as erythematous plaques, and because these lesions had been chronic and persistent, she was started on PUVA irradiation or narrow band UVB therapy.

Figure 1

(a) The biopsy specimen shows infiltration of atypical lymphocytes into the epidermis and upper dermis (hematoxylin and eosin stain). (b) Multiple nodules on the left side of her buttock. Black dots indicate the lesion of excisional biopsy. (c) The biopsy shows pseudoepitheliomatous hyperplasia (hematoxylin and eosin stain). (d) Atypical lymphoid cells had infiltrated into the upper dermis (hematoxylin and eosin stain). (e) A giant cell in the epidermis (hematoxylin and eosin stain). Immunohistochemical staining revealed that lymphocytes were positive for (f) CD4 and (g) CD8. (h) Tumor cells which are stained a blue color, expressed CD4 intermingled with CD8-positive cells shown by a brown color.

In 2017, she noticed multiple nodules on the left side of her buttock [Figure 1b]. Histopathological examination of a nodule revealed marked epidermal hyperplasia with hyperkeratosis [Figure 1c]. The upper dermis showed dense cellular infiltration consisting of both small lymphocytes and large atypical lymphocytes [Figure 1d]. A multinucleated giant cell was noted in the epidermis [Figure 1e]. The dermis was characterized by the presence of epithelioid cells associated with mixed inflammatory infiltrate such as neutrophils and eosinophils. Most of the dermal and epidermal lymphocytes were positive for CD4 [Figure 1f] and CD8 [Figure 1g], and scattered lymphocytes were positive for granzyme B. As shown in Figure 1h, large atypical tumor cells, which were stained a blue color, expressed CD4 intermingled with CD8-positive cells shown by a brown color. Based on these findings, we clarified that tumor cells were of CD4+ phenotype instead of CD8+ or CD4/CD8 double-positive cells. PAS-stained and Grocott-stained sections did not reveal any organisms. Thus, we diagnosed the patient as having mycosis fungoides associated with pseudoepitheliomatous hyperplasia.

Pseudoepitheliomatous hyperplasia is most commonly associated with mycobacterial and deep fungal infections, and the spectrum of associated disorders includes other infectious conditions such as viral, bacterial, protozoal, and spirochetal processes, as well as neoplastic and chronic inflammatory disorders.[12] Previously, a limited number of studies investigating the association between pseudoepitheliomatous hyperplasia and cutaneous lymphoma have been published.[13] These cases almost exclusively fall in the category of CD30-positive lymphoproliferative disorders, such as anaplastic large cell lymphoma and lymphomatoid papulosis. Other cutaneous lymphomas such as CD56-positive cytotoxic T-cell lymphoma and natural-killer (NK)/T cell lymphoma, nasal-type, and mycosis fungoides have rarely been reported.[4] Another intriguing finding in our case was a giant cell in the epidermis. This evidence together with the infiltration of CD8+ lymphocytes suggest that anti-tumor immunity may have promoted transepidermal elimination and thus may have resulted in the formation of pseudoepitheliomatous hyperplasia in our patient.

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