Surprises in scalp aspirations Dr. Gladwyn Leiman

Clinical History FNA of scalp: The patient is a 45 year old male who is both HIV positive (CDC Class A3 disease) and Hepatitis B positive. At the age of 17, he underwent removal of a pituitary tumor, and has required therapy for hypopituitarism and diabetes insipidus since that time. He has been HIV positive for ten years, and on highly active anti-retroviral therapy for seven years. Five years ago, he was treated for anal cancer by chemoradiation. His current illness commenced with very vague symptoms, including a mild vertical headache and "feeling funky" for a month. He sought therapy when he himself palpated two adjacent scalp masses on the vertex of his head. On examination, they were found to be soft, superficial and fluctuant, measuring individually 3.5 and 1.5 cm in diameter. They were situated in the parieto-frontal region of the scalp. Considering the HIV status, the initial clinical concern was that of an infectious process. Fine needle aspiration of the scalp masses was requested, with a particular note for material to be sent for culture. Slide 1 Click to view with ImageScope Click to view with a Web-Based Viewer Slide 2 Click to view with ImageScope Click to view with a Web-Based Viewer Cytological Findings: The two masses showed identical features. There was no evidence of infection. A background of blood was present, but was conspicuously free of an inflammatory cell component. The cells were of moderate size, and seen in large vessel-associated fragments, in syncytial aggregates, in small clusters, and rarely lying singly. Individual cells were characterized by moderately abundant basophilic cytoplasm with centrally and eccentrically placed relatively bland nuclei. Cell borders were not well identified. Most cells were mononuclear, but binucleate cells were observed. Nuclei were round to oval, with some accentuation of nuclear boundaries, and very finely granular to bland chromatin with small nuclei. Focally, intranuclear cytoplasmic invaginations were readily found. Mitotic figures were also observed, but not counted. Very rare cell whorls were identified, no more than one in each of the two sites aspirated. After full consideration of a list of differential diagnoses of lesions arising in skin, adnexae, subcutaneous tissue and bone, a diagnosis of meningioma was made. CT examination of the head was subsequently performed, showing a tumor with a large intracranial component, but without evidence of cranial shift or compression. Partial bone destruction was noted, with expansive growth of the tumor into the scalp area in two places, corresponding to the two masses identified and aspirated. The patient underwent a bifrontal parietal craniotomy with resection of the tumor through a very large skull flap. The operative diagnosis was that of a parafalcine meningioma with compression but no invasion of the underlying cortex. After several early postoperative complications, including subarachnoid hemorrhage and associated right-sided weakness, the patient made a slow but steady recovery. Four months later, he required radiosurgery for an area of residual tumor, but seven months postoperatively, he has made a full recovery without neurologic deficit. His scalp wound has healed well, and he continues on antiretroviral therapy. Surprises in Scalp Aspirations Discussion: Meningiomas are common brain tumors, but are uncommonly seen by cytopathologists if neurocytology is not part of the routine workload. They comprise 20% of brain tumors, and affect 6 per 100,000 of the population annually. They usually occur in adults, with a female predominance. Derived from arachnoid cells of the dura mater, meningiomas are generally indolent tumors, but may progress rapidly during pregnancy. Their slow growth is associated with vague symptomatology, usually related to compression of adjacent brain. They demonstrate a propensity to grow along external surfaces of the brain, within the ventricular system, and may extend through the skull, usually at the site of sagittal or coronal plate fusions. Most meningiomas are solitary, but multiple tumors are seen in up to 5% of patients. Similarly, they are usually benign, and are not considered to be malignant even if bone or skeletal muscle is invaded. Nevertheless, rare uncontested reports of metastasis to lung or mediastinum exist. Despite this caveat, they require resection if possible, as any intracranial tumor may lead to secondary obstructive or compressive phenomena. The most predictive factors of recurrence are incomplete resection and tumor grade. In Neuropathology departments, meningiomas are frequently encountered, aspirated, squashed or scraped, with the result that excellent cytologic descriptions exist for the various tumor subtypes. These include meningothelial, lymphoplasmacytic, lipomatous, fibroblastic, microcystic, psammomatous, xanthomatous, and transitional variants. For the cytopathologist not involved in neurocytology, however, the diagnosis of meningioma is challenging for a number of reasons. The first is the rarity with which these tumors occur outside the bony skull within reach of the general FNA cytopathologist; the second is the multiplicity of variants which may be encountered; and third is the extensive differential diagnosis which may exist in skin, scalp, and other head and neck locations where extracranial meningiomas may be found. Single case reports therefore exist in the cytologic literature of mesothelial encounters in the scalp, the parapharyngeal area, the orbit, the nasal region, as well as those seen in mediastinum, lung and pleural fluid. Despite the various sites at which they may occur, and despite the histological variants which exist, cytologic descriptions of meningiomas are nevertheless fairly consistent. They are described as being rounded or spindled cells, arranged in syncytial clusters, sheets and characteristic whorls, with psammoma bodies in a minority of cases. The nuclei are usually oval, well outlined, slightly eccentric, with bland to evenly distributed finely granular chromatin. Small nucleoli are frequently seen, and located centrally. In addition, nuclear grooves are sometimes observed. A very prevalent attribute is the presence of intranuclear cytoplasmic inclusions, which can, on occasion, be numerous. The cytological differential diagnosis can be tricky, depending on the location of the mass and the nature of the tumor. Tumors may be diagnosed mistakenly as squamous cell carcinomas (either cutaneous or metastatic, e.g. from the lung or esophagus) if the whorls are mis-assessed as keratin pearls. If the tumor is well endowed with intranuclear cytoplasmic inclusions and nuclear grooves, a primary or metastatic papillary carcinoma of the thyroid could be considered. In the upper neck region, these tumors need to be differentiated from paragangliomas. Depending upon the differential diagnosis established, it may be useful to prove that meningiomas are immunochemically positive for EMA, Vimentin, ER, PR and CD99, but negative for CEA, GFAP, TTF, thyroglobulin and calcitonin. Keratin stains are only focally positive, and only moderately often. The challenge in this particular case was the patient's history, not only of HIV with anticipation of an inflammatory lesion, but also his prior history of a brain tumor, the exact type of which is unknown. The fact that he had not had a prior skull Xray or CT, and the presence of two distinct scalp lesions, added to the difficulty of diagnosis. Finally, the fact that the characteristic whorls were so sparse made the final assessment somewhat onerous. The take home message of this case is that general cytopathologists, working outside neurocytology, should anticipate intracranial tumors with extracranial extension if they encounter relatively bland cytologic lesions with whorls, spindle cells and/or intranuclear inclusions almost anywhere over the vertex, or attached in some way to the base of the skull. References: Liwnicz BH, Henderson KS, Masukawa T, Smith RD. Needle aspiration cytology of intracranial lesions. A review of 84 cases. Acta Cytol 1982;26:779-786. 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