Intralymphatic Proliferation of T-cell Lymphoid Blasts in the Setting of Hidradenitis Suppurativa.

Intralymphatic proliferation of T-cell lymphoid blasts (IPTCLBs) is a rare, recently described entity, associated with cutaneous inflammatory conditions and characterized by intralymphatic proliferation of highly proliferating, blastoid T lymphocytes expressing CD30, thus mimicking an intravascular lymphoma. In all reported cases, the intralymphatic proliferation was associated with an underlying inflammatory condition, with no clonal T-cell receptor rearrangement, no signs of systemic or cutaneous lymphoma, and excellent prognosis. The authors present a new case of IPTCLB arising in a patient with hidradenitis suppurativa. Histological examination revealed a dilated follicle embedded within a fibrotic stroma surrounded by a dense lymphoid infiltrate characterized by the presence of dilated small vessels filled with atypical medium-to-large sized blastoid lymphocytes expressing a CD4 T phenotype. There was also expression of CD30, but negativity for cytotoxic markers and Epstein-Barr virus. The proliferation index was high and the vessels showed expression of D2-40, confirming their lymphatic nature. No signs of systemic lymphoma could be detected after routine investigations, and the patient is alive and in good general health. IPTCLB is a rare benign entity that presents with worrying, potentially misleading histopathological features that mimic those observed in intravascular lymphoma. Careful histological and phenotypic investigations and correlation with the clinical features are necessary for a proper diagnosis.