Diagnostic Cytopathology: Something for Everyone
Moderator: Dr. Celeste N. Powers
Surprises in scalp aspirations
Dr. Gladwyn Leiman
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.
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
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
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