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.

We studied 53 cutaneous lymphoproliferative disorders, all of which manifested hair follicle hyperplasia. There were 42 cases conforming to the description of pseudolymphomatous folliculitis (PLF) and 11 cases of authentic lymphomas including mycosis fungoides, CD30+ anaplastic large cell lymphoma, diffuse large B-cell lymphoma, B-cell small cell lymphoma/leukemia, and peripheral T-cell lymphoma, not otherwise specified. All patients with PLF clinically presented with a solitary nodule preferentially involving the face. Beside hair follicle hyperplasia, the typical features were a dense infiltrate of small well-differentiated lymphocytes, lymphoplasmacytoid cells, plasma cells, and epithelioid histiocytes forming tiny granulomas. Some unusual or worrisome features recognized included eccrine/apocrine duct hyperplasia, subcutis/muscle infiltration, lymphocyte "smudging," single file infiltration, and large atypical cells. Immunohistochemically, T-cell predominant cases dominated in the series. All 34 tested cases revealed a polyclonal pattern of kappa and lambda immunoglobulin (Ig) light chain expression. In 4 cases, scattered CD30+ cells were identified. Monoclonal rearrangements of T-cell receptor (TCR) and IgH genes were detected in 19 and 3 cases respectively, including 1 case with dual T-cell receptor/IgH rearrangement. Three of 30 tested cases proved positive for herpes simplex virus-1, whereas herpes simplex virus-2 always tested negative. Of 31 cases tested for Borrelia burgdorferi, 30 specimens were negative. In 9 cases, fluorescent in situ hybridization for t(11;18) and t(14;18) revealed none of the above translocations. The most common treatment modality was surgical removal. Forty patients with a mean follow-up of 3.7 years included 39 patients with no evidence of disease and 1 individual with local recurrence. The comparison of "clonal cases of PLF" and those with polyclonal population or in which clonality remained undetermined revealed no differences between the 2 groups in the clinical presentation, pathologic, and immunohistochemical features. We conclude that hyperplasia of hair follicles and other adnexa can be seen not only in the condition currently known as PLF, but also in genuine cutaneous lymphomas and may be just a happenstance secondary to a basic pathologic process.