Publication:

Zosteriform lichen planus preceding ipsilateral breast carcinoma: a possible paraneoplastic association

Lichen planus (LP) is a chronic, T-cell-mediated inflammatory dermatosis involving the skin and mucous membranes, with multiple clinical variants. Zosteriform lichen planus (ZLP) is a rare variant characterized by a unilateral, dermatomal or band-like distribution that may mimic herpes zoster. While mucosal LP, particularly oral lichen planus, has been associated with malignancy, the role of cutaneous LP, especially ZLP as a paraneoplastic manifestation remains unclear. A 54-year-old woman presented with a one-year history of asymptomatic violaceous papules and plaques arranged in a unilateral, band like pattern over the left chest extending to the neck, without crossing the midline. The distribution corresponded to C3-T2 dermatomes. Mucosa, scalp, and nails were uninvolved. Clinical findings suggested zosteriform lichen planus, which was confirmed on histopathology. During follow-up, six months after the onset of cutaneous lesions, the patient developed a palpable lump in the left breast. Imaging revealed a suspicious lesion, and histopathology examination confirmed invasive ductal carcinoma. Notably, the malignancy was ipsilateral to the cutaneous eruption. The temporal sequence, strict dermatomal localization, and absence of known triggers raised suspicion of a paraneoplastic association. The association between LP and malignancy is controversial, with stronger evidence for oral LP and lichen planus pemphigoides. In this case, a neuro-immunologic mechanism may be implicated, wherein tumour related immune activation selectively affects contiguous dermatomes, leading to a localized lichenoid eruption. To our knowledge, ZLP has not previously been reported as a paraneoplastic manifestation. This case highlights a rare presentation of ZLP potentially associated with underlying breast carcinoma and suggests a possible paraneoplastic role.