Case Number : Case 756 - 10th May Posted By: Guest

Lymphoid proliferation with a T cell pattern. Small to medium lymphocytic infiltrate with atypical irregular nuclei. Some epidermotropism. Could be primary cutaneous CD4 positive small/medium TCL (as lesions are usually solitary or localized) or T cell pseudolymphoma (lymphomatoid drug reaction). I think the idea of a single lesion of tumor stage MF without the clinical setting of patches and plaques else where is no more accepted. Will do: CD2, CD3, CD5, CD4 and CD8and TCR gene rearrangement studies.

? T cell lymphoma. Needs lymphoma panel.

Folliculotrophic MF

Solitary lesion with a top heavy dense infiltrate with some epidermotropism. Agree with Mona, but thinking this might be a pseudo!!

I think it's a pseudolymphoma. A top-heavy, folliculocentric and epidermotropic dense infiltrate of lymphocytes. I would expected, in a folliculotropic mycosis fungoides, mucinous expanded follicles or pilocentrism without epidermotropism. Also, intraepidermal lymphocyes are not larger than dermal lymphocytes.
This hypothesis is supported by the history case of a solitary nodule on the head, an uncommon presentation of a cutaneous lymphoma.

Pseudolymphoma. I think it could be lupus erythematous with an uncommonly dense perifollicular lymphoid infiltrate or a pseudolymphomatous folliculitis.

It was a mixed infiltrate of B-cells, T-cells including CD4 and CD8 (no particular predominance). We did not peform PCR. The solitary nature, location and distribution of the cells might make you suggest a distinctive clinicopathological lesion in the literature (pretty uncommon).

LPLK.

I agree this is most likely LPLK, with the differential including an unusual clinical presentation of lichen planopilaris.

- There is specific targeting of the epidermis and especially the follicular infundibula.
- Follicles show keratin plugging and hypergranulosis with lichen-planus like epidermal changes.
- No perieccrine or sebaceous adnexal infiltrate. No perivascular infiltrate. (these would be expected in lupus).
- There is a foreign body granuloma adjacent to the bottom-left edge of the infiltrate.

Primary cutaneous follicle center lymphoma?

Majocchi´s granuloma

Given the immunophenotyping results, the mixed T and B cell population, I would suggest: Pseudolymphomatous folliculitis.

Well done Mona!! although I think we had some very good alternate suggestions and discussion.

We also favoured pseudolymphoma and Dr Saleem Taibjee specifically raised the possibility of pseudolymphomatous folliculitis. We shared the case with Dr Dmitry Kazakov who agreed and speculated that the numerous fungal spores in the follicular infundibula (on PAS, and in the last image) may be relevant. A pseudolymphomatous variant of LPLK would certainly be a good alternate suggestion. I put this case in to draw your attention to pseudolymphomatous folliculitis.

References
Arai E, Okubo H, Tsuchida T, Kitamura K, Katayama I. Pseudolymphomatous folliculitis: a clinicopathologic study of 15 cases of cutaneous pseudolymphoma with follicular invasion. Am J Surg Pathol. 1999 Nov;23(11):1313-9.

Kazakov DV, Belousova IE, Kacerovska D, Sima R, Vanecek T, Vazmitel M, Pizinger K, Michal M. Hyperplasia of hair follicles and other adnexal structures in cutaneous lymphoproliferative disorders: a study of 53 cases, including so-called pseudolymphomatous folliculitis and overt lymphomas. Am J Surg Pathol. 2008 Oct;32(10):1468-78.

Great case, many thanks Dr. Carr and Dr. Taibjee