Injection site pseudosarcoma in piriformis syndrome

Subcutaneous infiltrative nodule at the injection site of low-molecular weight heparin simulating malignancy

Low-molecular weight heparins (LMWHs) are the standard agents used for the prevention and treatment of thromboembolic disorders. Despite their widespread use, reports on adverse effects from LMWHs are uncommon. The present report describes a 23-year-old woman with a 3.8-cm solitary, fibrofatty, poorly demarcated nodule involving the subcutaneous tissue of the infraumbilical abdominal wall that appeared 4 years after iterative local administration of LMWH. Microscopically, the nodule showed atypical cells, with bizarre nuclei in the septa of cellular fibrous tissue dissecting the adipose lobules, in the absence of any other malignant changes. To the best of our knowledge, this kind of LMWH-related lesion has not been previously reported. The lesion may result from the combination of an idiosyncratic reaction to the LMWH with local trauma being a probable promoting factor. Alternatively, this reactive proliferation may be entirely due to the trauma represented by repeated injections. This rare process could easily be confused with liposarcoma. As the clinical history of injections is often not provided in the requisition form, pathologists should be aware of this adverse effect from LMWH to avoid misdiagnosis and excessive treatment.