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Case Reports

Abstract

Encapsulated fat necrosis (EFN) is an uncommonly diagnosed cutaneous condition, usually presenting as firm nodules on the lower extremities. They are associated with repetitive minor trauma and intramuscular injections but are not known to be associated with any oral medications. We present the case of an 87-year-old woman with diffuse large B-cell lymphoma and chronic lymphocytic leukemia. Initially her leukemia was treated with Imbruvica, a Bruton’s tyrosine kinase inhibitor, but due to poor tolerance, she switched to oral Venetoclax, a selective BCL-2 inhibitor. A follow-up bone marrow biopsy one year later showed significant reduction of disease, and she has remained on Venetoclax since. A year later, multiple mobile nodules up to 1.5 cm in size were noticed across her upper body, especially on her forearms, clinically thought to represent lipomas or pilomatricomas. Punch biopsies were obtained from two nodules on her left dorsal forearm. The first lesion demonstrated a superficial encapsulated nodular proliferation of fatty tissue with myxoid degeneration, fat necrosis with calcifications, and thin fibrous septae.  The second lesion had a similar appearance but lacked internal fibrous septae or calcifications. The diagnosis of encapsulated fat necrosis was rendered for both specimens. Given the unusual location and multifocality, as well as the lack of any other precipitating factors, these lesions were suspected to be treatment-induced. We present this case to raise awareness of this previously unrecognized potential side-effect of Venetoclax as EFN may clinically mimic a neoplasm.