Persistent Agmination of Lymphomatoid Papulosis with Features of Lymphomatoid Papulosis in Both the Regressing Papular Component and the Persistent Patch: A Case Report and Review of the Literature.

Persistent agmination of lymphomatoid papulosis (PALP) is a rare, anatomically localized variant of lymphomatoid papulosis (LYP) characterized by clustered papules superimposed on a chronic persistent patch or plaque which resembles cutaneous T-cell lymphoma. The histologic patterns may be variable, and differentiation from early-stage cutaneous T-cell lymphoma (CTCL), particularly unilesional mycosis fungoides (MF), can be challenging. We report an 18-year-old woman with a longstanding CD8-positive T-cell dyscrasia, initially diagnosed at age 10 as Type B LYP showing folliculocentricity. She experienced a recurrence at age 14, and 3 years later she developed a persistent, localized patch on the thigh with superimposed papules which exhibited a waxing and waning course. Histologic examination of both the persistent patch and episodic papular component revealed a very similar morphology which was the one manifesting an overlapping morphology of Type B LYP and pityriasis lichenoides chronica (PLC); there was follicular involvement similar to the earlier 2016 biopsy. PALP is a very rare variant of LYP with most of the reported cases describing the persistent patch as having features of cutaneous T-cell lymphoma, typically mycosis fungoides. We describe a patient with PALP where both the episodic papules and the persistent patch showed a similar histomorphology which in turn mirrored the previous pathology from 2016 that was characteristic for LYP clinically and was biopsy proven folliculotropic Type B LYP. Two other cases of PALP showing a persistent patch with classic features of LYP have been previously published. Hence, there is a subset of PALP where the persistent lesion is compatible with LYP as opposed to being one of lymphoma. The persistence of LYP challenges this conceptualization of LYP as a lymphoproliferative disorder where complete regression is a requisite.