Folliculotropic mycosis fungoides C84.0

Rare variant of a CD4-positive, cutaneous T-cell lymphoma of the mycosis fungoides type, which is characterized by a particular epitheliotropy (adnexotropy), often leaving out the epidermis (smooth epidermis)

See below Cutaneous T-cell lymphomas. This cutaneous T-cell variant was described after organ transplantation (Spence-Shishido A et al. 2015).

On neck, nape, face and capillitium localized, 2.0-10.0 cm large, mostly blurred, slightly reddened or reddish-brown or grayish-brown, clearly pruritic (rarely asymptomatic), little protruding from the skin level plaques with mostly skin-colored, 0.1-0.2 cm large, always follicular, pointed conical, rough horny papules (clinical picture of the so-called mucinosis follicularis). Not infrequently, evidence of lesional comedones and cysts; when affecting the face, also "acne-like" pictures (Shamim H et al. 2021). Lesional alopecia may occur at the capillitium, which may be reminiscent of alopecia areata.

Not infrequently, alopecia of the eyebrows may occur in the early stages.

In the advanced stage of the disease, the plaques and nodules emerge more clearly from the skin level.

Histology: Follicular lymphocytic infiltrate from small to medium sized lymphocytes (these often have cerebriform nuclei). An epidermotropy is usually absent or only very focally detectable. Adnexal epithelia initially appear hyperplastic and later destroyed (image of mucinosis follicularis). Sometimes only individual epithelial bandages are detectable.

Some cases are characterized by a preferential syringotropy (older name: syringotropic MF).

Immunohistology: The tumor cells are CD3 positive, CD4 positive and CD8 negative as in classical MF. An admixture of CD30+ cells can be observed.

The clinical picture with the follicular, in the lateral view particularly prominent, pointed, skin-colored, less inflammatory but itchy horny papules (patient comes because of itching!) is characteristic. The histological pattern is also typical. However, it takes an average of 3.9 years (!) before a diagnosis is made.

• S.u. Mycosis fungoides.
• Stage scheme:
  • Initial strict local therapy with PUVA or narrow band UVB and glucocorticoid externa.
  • In case of progression of MF: PUVA in combination with retinoids ( Acitretin: the effective dose is above 10 mg/day. The optimum effect is about 50 mg/day depending on body weight).
  • In case of progression of MF: combination of PUVA and interferon alpha (dosage: 3.0-5.0 million IU, 3 times/week s.c.); in addition: local X-ray irradiation (3.0-5.0 Gy) by means of linear accelerators or conventional X-ray equipment.
  • In stage IIb (see cutaneous T-cell lymphomas): chemotherapy (CHOP, doxorubicin, gemcitabine; see cytostatics below): poor response.
  • Experimental: allogeneic stem cell transplantation.

Approximately analogous prognosis compared to "classic" mycosis fungoides. The 5-year survival rate in stage IIA is 87%, in stage IIb 83%. In patients with more extensive plaques of folliculotropic MF, survival is expected to be analogous to patients with tumor-stage MF. The 10-year survival rate for this collective is 25% (van Santen S et al. 2016).

The therapeutic response to the usual standard therapies is considered to be somewhat worse compared to "classic MF" (van Santen et al. 2017). In this respect, early "aggressive topical radiotherapy" is recommended in case of localized manifestation .

Similar cases have been described as "folliculocentric or pilotropic MF." It is likely that a relevant proportion of patients classified under the clinical picture of mucinosis follicularis must actually be evaluated as folliculotropic T-cell lymphoma.

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