An indolent T-cell lymphoproliferative disorder

Clinical features

•2M:1F

•Crops of rapidly growing, self-healing, pink papules up to 1.0 cm diameter

•Heal with atrophic scars

•Occasionally large nodules

•Trunk & limbs are sites of predilection

•Regional variant

•Exceptional mucosal involvement

•Follicular variant

•Pustular variant

•Self-limiting or protracted course

•Up to 20% associated with mycosis fungoides, primary cutaneous anaplastic large cell lymphoma or Hodgkin lymphoma

Histological features

•Subdivided into 5  major  & several rarer variants

•Type A: 75-80%, wedge shaped infiltrate with base uppermost, large, anaplastic cells with abundant cytoplasm and vesicular nuclei containing prominent nucleoli, can resemble Reed-Sternberg cells, conspicuous mitoses & background infiltrate of lymphocytes, plasma cells, histiocytes, neutrophils & eosinophils

•Type B: 5-10% resembles plaque stage mycosis fungoides

•Type C: 7-10% nodular infiltrate similar to primary cutaneous anaplastic large cell lymphoma

•Type D: epidermotropic form composed of CD8 T cells

•Type E: angioinvasive & angiodestructive

•Type F folliculotropic variant often with follicular mucinosis 

•Mixed variants are not uncommon

•Myxoid, sarcomatous variant

•Syringotropic variant

•Variable epidermal necrosis, epidermotropism, edema,  hemorrhage & vasculitis/thrombosis

•CD4, CLA, MUM1 +ve

•CD8-ve (except for types D & E variants)

•Exceptional. CD4+/CD8+ & CD4-/CD8- variants

•Granzyme-B, TIA-1 & perforin +ve)

•CD45, CD30 +ve/CD15 –ve (types A & C)

•Type B often CD30-ve

•Generally, ALK  & EMA  -ve

•Variable CD56+ve

Differential diagnosis

There is considerable overlap with primary cutaneous anaplastic large cell lymphoma & transformed mycosis fungoides. Distinction can be readily made in the majority of cases with clinicopathological correlation.

CD30+ve cells may be seen in a wide range of infections including molluscum contagiosum, herpes simplex, Milker’s nodule, EBV, HTLV-1, HIV, scabies & syphilis. CD30+ve cells may also be seen in PLEVA & drug reactions

Type B variant is histologically indistinguishable from mycosis fungoides. Type D variant is indistinguishable from other epidermotropic lymphomas.