Intraosseous Angiolipoma of the Cranium: Case report and review of the literature.

The authors report a rare case of a calvarial osseous lesion in the setting of a male patient with invasive ductal breast carcinoma. The calvarial lesion was resected to alleviate symptoms of raised intracranial pressure, with histology revealing an angiolipoma. The authors report a peculiar event where two unrelated extremely rare tumors have been identified concomitantly. The incidence of male breast cancer in the general US population is < 1%.[3] Angiolipoma is a benign tumor generally found in subcutaneous tissue, with one other cranial intraosseous lesion reported in literature.[6] The authors initially favored a diagnosis of metastasis to the calvarium, but following an excision biopsy, turned out to be an intraosseous angiolipoma. As physicians, we are trained to utilize the principles of diagnostic parsimony. When faced with clinical dilemmas in patients with multiple problems, the medical adage “when you hear hoof beats behind you, think horses, not zebras”, comes to mind. A few years ago I had the opportunity to partake in the treatment of a 50 year old female patient presenting with an acute history of raised intracranial pressure, in the absence of any neurological deficit. Her magnetic resonance imaging (MRI) revealed a small left intraventricular lesion (measuring 1.7 × 1.7 cm) without hydrocephalus, a computed tomography (CT) scan of her chest, abdomen, and pelvis revealed a concomitant renal cell mass. On imaging, the intraventricular mass appeared characteristic of a left atrial meningioma. Faced with the uncertainty of a clear diagnosis, a whole body (18) F fluoro 2 deoxy d glucose positron emission tomography scan (FDG PET) and an Indium111 octreotide brain scintigraphy (OBS) imaging were performed. The ability to differentiate a benign (meningioma) from a malignant (renal cell carcinoma) metastatic lesion using the information obtained would help decide a management strategy. The FDG PET and OBS imaging was discordant for these lesions, the renal mass was positive (increased uptake) on the FDG PET and negative (absence of tracer uptake) on OBS study. The intraventricular lesion was positive on the OBS study and negative on the FDG PET scan. She underwent a nephrectomy with a diagnosis of renal cell carcinoma. The imaging results favored an intraventricular meningioma, the small tumor size and absence of hydrocephalus made Gamma Knife Radiosurgery (GKRS) with 13 Gy to the 51 isodose line (IDL), the initial treatment of choice. About 14 months later, she presented with recurrent symptoms of raised intracranial pressure, her MRI revealing an increase in the size of the intraventricular lesion along with hydrocephalus. The tumor was now amenable to surgery and she underwent a left temporal lesionectomy, histopathology confirming a renal cell carcinoma metastatic lesion. She underwent GKRS to the resection cavity bed, receiving 15 Gy to the 51 IDL and without any subsequent intraventricular recurrence. Metastatic lesions from renal cell carcinoma have a propensity to present as late as 10 years following diagnosis of the primary tumor, even though they are the fourth most common to metastasize to the brain.[5] The combined use of noninvasive imaging modalities, OBS, and FDG PET that are presently available have been reported to significantly increase diagnostic sensitivity and specificity for intracranial meningiomas. These tests have enabled differentiation of benign from malignant tumors, and have been used in the presence of multiple tumors, to identify tumor grade and possibly providing evidence suggesting a collision tumor.[2,4] The high index of suspicion for a particular diagnosis may be reenforced with the use of noninvasive testing, especially in circumstances where observation, stereotactic radiosurgery, or alternative medical treatment options are available. The authors’ in their case report conclude that were it not for a histological diagnosis, they would have assumed the calvarial lesions to be metastatic. In our case, the evidence favored a benign intraventricular lesion but final histopathology revealed it to be metastatic. Modern imaging techniques provide a basis for narrowing the differential diagnosis but none of the modalities can presently be considered to be sensitive and specific enough to replace a tissue diagnosis. Although surgical interventions ranging from diagnostic stereotactic biopsy to open excision biopsy is associated with risks, histopathological diagnosis remains the gold standard. The patient should be made aware of the risk benefit ratio of their investigations, interventions, and play a part in deciding the most suitable management options available to them. This case report indirectly emphasizes the importance of a judicious tissue diagnosis from intracranial lesions. We always strive to avoid harm to our patients and aim to provide them with safe, cost effective, and beneficial treatments. As treating surgeons, we face challenging situations in evaluating patients’ with complex and multiple medical problems, so when we ‘hear hoof beats, we have to think of both horses and zebras’. Herein lies the importance of experience and clinical judgment, enabling us to decide how and when to use laboratory tests, imaging, and appropriately time surgical interventions.[1] To quote from Sir William Osler “The value of experience is not in seeing much, but in seeing wisely”.