Tumour mimic in dermatopathology

A 72-year-old White woman, with a background of chronic inflammatory demyelinating polyradiculoneuropathy, presented with a large violaceous patch on the left upper inner thigh, surrounded by multiple satellite brown macules and petechial lesions. The patient described a long-standing ‘birthmark’ at the site since childhood, with gradual development of pinpoint satellite lesions over 18 months and a newer painful boggy swelling involving the left buttock evolving over 6 months. This clinically raised concern for angiosarcoma, haematoma or another vascular neoplasm. Examination demonstrated a vascular-appearing erythematous lesion on the medial thigh with prominent violaceous discoloration, petechiae extending down the thigh, and a soft boggy buttock swelling with overlying blue-purple hue. There was no lymphadenopathy present. Three punch biopsies from the left medial thigh (upper and lower) and left buttock showed similar histological features: normal epidermis with a dense lymphohistiocytic infiltrate in a lichenoid, perivascular and periadnexal distribution, with a prominent granulomatous component and conspicuous haemosiderin-laden macrophages. Interface vacuolar change and keratinocyte apoptosis were absent, and eosinophils were rare. No evidence of vasoformative malignancy or atypical endothelial proliferation was identified. The overall features supported a diagnosis of granulomatous pigmented purpuric dermatosis (GPPD), a rare variant of pigmented purpuric dermatosis. In this case it presented with striking tumour-mimicking clinical morphology in the context of a presumed congenital vascular patch. This case is significant as pain and tumour-mimicking vascular clinical appearances are distinctly uncommon in GPPD, broadening the recognized clinicopathological spectrum and highlighting the importance of biopsy in excluding malignancy and preventing unnecessary aggressive management.

Abstract from Crossref