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Selected References

Metastatic Lesions

Overview

Bekaert L et al: Histopathologic diagnosis of brain metastases: current trends in management and future considerations. Brain Tumor Pathol. 34(1):8-19, 2017

Dagogo-Jack I et al: Treatment of brain metastases in the modern genomic era. Pharmacol Ther. 170:64-72, 2017

Lowery FJ et al: Brain metastasis: unique challenges and open opportunities. Biochim Biophys Acta. 1867(1):49-57, 2017

Mostofa AG et al: The process and regulatory components of inflammation in brain oncogenesis. Biomolecules. 7(2), 2017

Schrijver WA et al: Unravelling site-specific breast cancer metastasis: a microRNA expression profiling study. Oncotarget. 8(2):3111-3123, 2017

Spreafico F et al: Proteomic analysis of cerebrospinal fluid from children with central nervous system tumors identifies candidate proteins relating to tumor metastatic spread. Oncotarget. ePub, 2017

D'Souza NM et al: Combining radiation therapy with immune checkpoint blockade for central nervous system malignancies. Front Oncol. 6:212, 2016

Wesseling P et al: Metastatic tumours of the CNS. In: Louis DN et al (eds), WHO Classification of Tumours of the Central Nervous System. Lyon, France: International Agency for Research on Cancer, 2016, pp 338-341, 2016

Lin NU et al: Response assessment criteria for brain metastases: proposal from the RANO group. Lancet Oncol. 16(6):e270-8, 2015

Parenchymal Metastases

Balendran S et al: Next-generation sequencing-based genomic profiling of brain metastases of primary ovarian cancer identifies high number of BRCA-mutations. J Neurooncol. ePub, 2017

Bekaert L et al: Histopathologic diagnosis of brain metastases: current trends in management and future considerations. Brain Tumor Pathol. 34(1):8-19, 2017

Sandler KA et al: Treatment trends for patients with brain metastases: does practice reflect the data? Cancer. 123(12):22742282, 2017

Leptomeningeal Metastases

Boire A et al: Complement component 3 adapts the cerebrospinal fluid for leptomeningeal metastasis. Cell. 168(6):1101-1113.e13, 2017

Le Rhun E et al: Neoplastic meningitis due to lung, breast, and melanoma metastases. Cancer Control. 24(1):22-32, 2017

Hyun JW et al: Leptomeningeal metastasis: clinical experience of 519 cases. Eur J Cancer. 56:107-14, 2016

Smalley KS et al: Managing leptomeningeal melanoma metastases in the era of immune and targeted therapy. Int J Cancer. 139(6):1195-201, 2016

Miscellaneous Metastases

Chen H et al: A rare case of small cell carcinoma of lung with intraventricular metastasis. Br J Neurosurg. 1-3, 2017

Konstantinidis L et al: Intraocular metastases--a review. Asia Pac J Ophthalmol (Phila). 6(2):208-214, 2017

Sánchez Orgaz M et al: Orbital and conjunctival metastasis from lobular breast carcinoma. Orbit. 1-4, 2017

Wendel C et al: Pituitary metastasis from renal cell carcinoma: description of a case report. Am J Case Rep. 18:7-11, 2017

Direct Geographic Spread From Head and Neck Neoplasms

Dundar Y et al: Skull base invasion patterns and survival outcomes of nonmelanoma skin cancers. J Neurol Surg B Skull Base. 78(2):164-172, 2017

Tashi S et al: The pterygopalatine fossa: imaging anatomy, communications, and pathology revisited. Insights Imaging. 7(4):589-99, 2016

Perineural Metastases

Badger D et al: Imaging of perineural spread in head and neck cancer. Radiol Clin North Am. 55(1):139-149, 2017

Barrera-Flores FJ et al: Perineural spread-susceptible structures: a non-pathological evaluation of the skull base. Eur Arch Otorhinolaryngol. 274(7):2899-2905, 2017

Moghimi M et al: Perineural pseudoinvasion: an unusual phenomenon in nonmalignancies. Adv Anat Pathol. 24(2):88-98, 2017

Panizza BJ: An overview of head and neck malignancy with perineural spread. J Neurol Surg B Skull Base. 77(2):81-5, 2016

Paraneoplastic Syndromes

Kelley BP et al: Autoimmune encephalitis: pathophysiology and imaging review of an overlooked diagnosis. AJNR Am J Neuroradiol. 38(6):1070-1078, 2017

Mauermann ML: Neurologic complications of lymphoma, leukemia, and paraproteinemias. Continuum (Minneap Minn). 23(3, Neurology of Systemic Disease):669-690, 2017

Sundermann B et al: Imaging workup of suspected classical paraneoplastic neurological syndromes: a systematic review and retrospective analysis of 18F-FDG-PET-CT. Acad Radiol. ePub, 2017

Fanous I et al: Paraneoplastic neurological complications of breast cancer. Exp Hematol Oncol. 5:29, 2016

Paraneoplastic Encephalitis/Encephalomyelitis

Fanous I et al: Paraneoplastic neurological complications of breast cancer. Exp Hematol Oncol. 5:29, 2016

Masangkay N et al: Brain 18F-FDG-PET characteristics in patients with paraneoplastic neurological syndrome and its correlation with clinical and MRI findings. Nucl Med Commun. 35(10):1038-46, 2014

Miscellaneous Paraneoplastic Syndromes

Martinez-Hernandez E et al: Clinical and immunologic investigations in patients with stiff-person spectrum disorder. JAMA Neurol. 73(6):714-20, 2016

van Sonderen A et al: From VGKC to LGI1 and Caspr2 encephalitis: the evolution of a disease entity over time. Autoimmun Rev. 15(10):970-4, 2016

Nonneoplastic Cysts

There are many types of intracranial cysts. Some are incidental and of no significance. Others may cause serious—even life-threatening—symptoms.

In this chapter, we consider a number of different intracranial cysts: cysticappearing anatomic variants that can be mistaken for disease, congenital/developmental cysts, and a variety of miscellaneous cysts. We exclude parasitic cysts, cystic brain malformations, and cystic neoplasms, as they are discussed in their respective chapters.

The etiology, pathology, and clinical significance of nonneoplastic intracranial cysts are so varied that classifying them presents a significant challenge.

In a schema based on etiology, cysts are classified as normal anatomic variants (e.g., enlarged perivascular spaces), congenital lesions derived from embryonic ectoor endoderm (colloid and neurenteric cysts), developmental inclusion cysts (e.g., dermoid and epidermoid cysts), and miscellaneous cysts that don't easily fit into any particular category (such as choroid plexus and tumor-associated cysts). Etiology is interesting but unhelpful in establishing an imaging-based diagnosis.

Categorizing cysts by the histologic characteristics of their walls—as is traditional in neuropathology texts—is again of little help when faced with the challenge of providing an appropriate differential diagnosis based on imaging findings alone.

An imaging-based approach to the classification of intracranial cysts is much more practical, as most intracranial cysts are discovered on CT or MR examination. This approach takes into account three easily defined features:

(1) anatomic location, (2) imaging characteristics (i.e., density/signal intensity of the contents, presence/absence of calcification and/or enhancement), and (3) patient age. Of these three, anatomic location is the most helpful

(Table 28-1).

While many types of intracranial cysts occur in more than one anatomic location, some sites are "preferred" by certain cysts. In this chapter, we discuss cysts from the outside in, beginning with scalp and intracranial extraaxial cysts before turning our attention to parenchymal and intraventricular cysts.

There are four key anatomy-based questions to consider about a cysticappearing intracranial lesion (see below). A summary chart based on these simple questions, together with the cysts discussed throughout the text, is included on the next page (Table 28-1).

FOUR KEY ANATOMY-BASED QUESTIONS

•Is the cyst extraor intraaxial?

•Is the cyst supraor infratentorial?

•If the cyst is extraaxial, is it midline or off-midline?

•If the cyst is intraaxial, is it in the brain parenchyma or inside the ventricles?

important scalp lesions in children include cephalocele and sinus pericranii.

The three statistically most common scalp cysts are epidermoid cyst (50%), trichilemmal cysts (25-30%), and dermoid cysts (20-25%). Epidermoid and dermoid cysts are discussed later in the chapter. We discuss trichilemmal (pilar or "sebaceous") cysts of the scalp here.

Scalp Cysts

Overview

A number of benign cutaneous cysts can present as scalp lesions. Most are not deliberately imaged, as the scalp is easily accessible to both visual and manual inspection. Nevertheless, scalp masses are not uncommonly identified on imaging studies intended to visualize intracranial structures. Imaging also becomes important when a scalp lesion is clinically felt to be potentially malignant, has a vascular component, or might be in anatomic continuity with intracranial contents.

Age is helpful in the differential diagnosis of nontraumatic scalp masses. In adults, the differential diagnosis includes skin carcinomas (basal and squamous cell), dermoid and epidermoid cysts, hemangiomas, and metastases. Trichilemmal ("sebaceous") cysts are common scalp masses in middle-aged and older patients.

The most common scalp mass in children is Langerhans cell histiocytosis, followed by epidermoid and dermoid cysts, scalp hemangiomas, and neurofibromas. Less common but

Trichilemmal ("Sebaceous") Cyst

Terminology

Although the term "sebaceous cyst" is commonly used by radiologists, this type of cyst does not actually contain sebaceous material. Such cysts are more accurately called trichilemmal cysts (TCs). Rarely, TCs enlarge and proliferate. Proliferating TCs are known as pilar ("turban") tumors. Malignant TCs are referred to as "proliferating trichilemmal cystic carcinoma."

Etiology

TCs are derived from the outer root sheath of hair follicles, not sebaceous glands.

Pathology

As only 0.3% of sebaceous cysts sent for pathologic examination are malignant, routine pathologic evaluation of sebaceous cysts is now considered necessary only when clinical suspicion of malignancy exists. In such cases, the most common neoplasm is squamous cell carcinoma.

Location, Size, and Number. Most TCs are found within the dermis or subcutaneous tissue. They can be single or multiple and vary from a few millimeters to several centimeters.

Gross and Microscopic Features. TCs are characterized by a fibrous capsule lined by stratified squamous epithelium. The cyst contents consist primarily of waxy desquamated keratin. Lobules of squamous epithelium in the cyst wall suggest a proliferating TC.

Clinical Issues

Epidemiology and Demographics. TCs affect 5-10% of the population. Although they can occur at any age, most occur in elderly women.

Presentation and Natural History. TCs generally appear as hairless, mobile, slightly compressible, subcutaneous scalp masses.

Nonneoplastic Cysts

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TCs grow slowly and have often been present for years. Rarely, they become locally aggressive and may even invade bone. Malignant degeneration with distant metastasis is rare.

Treatment Options. Surgical excision is the major treatment. Incomplete excision may result in recurrence.

Imaging

General Features. These scalp masses are generally large, well-delineated, round or ovoid, but somewhat complexappearing lesions.

CT Findings. TCs are sharply delineated solid, cystic, or mixed solid-cystic masses that are hyperdense compared with subcutaneous fat. Calcification is common and may be seen in punctate, curvilinear, or coarse forms (28-1A). Sometimes calcifications layer in the dependent portion of larger cysts. Typical TCs do not enhance, nor do they remodel or invade the underlying calvaria.

(28-1A) NECT with bone window in a patient being imaged for acute stroke shows incidental finding of five trichilemmal cysts. Two contain calcifications, whereas the other three do not. The underlying skull is normal. (28-1B) Axial T1WI in the same case shows that the well-delineated scalp cysts are isointense with brain.

(28-1C) Most of the larger cysts appear quite hypointense on T2WI. One of the smaller cysts is heterogeneously hypointense . (28-1D) The cysts are hypointensecompared with brain on FLAIR. The patient's acute infarct is seen as cortical hyperintensity .

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MR Findings. TCs are well-circumscribed scalp masses that appear incompletely surrounded by fat (28-1B). They are generally isointense with brain and muscle on T1WI and inhomogeneously hypointense on T2WI (28-1C).

TCs do not suppress on FLAIR (28-1D). "Blooming" foci on T2* (GRE, SWI) are caused by calcifications, not hemorrhage.

Simple uncomplicated TCs do not enhance, although the proliferating variant may show significant enhancement with solid lobules interspersed with nonenhancing cystic foci.

Differential Diagnosis

In adults, the imaging differential diagnoses are benign and malignant scalp tumors. Basal cell carcinomas and scalp metastases are ill-defined, poorly delineated scalp masses that invade the subcutaneous soft tissues and may erode bone. Superficial ulceration is common. Dermoid and

epidermoid cysts as well as hemangiomas are all much more common in the skull than in the scalp.

TCs are rare in children. In this age group, the most important lesions to differentiate from benign scalp cysts (usually dermoids/epidermoids, not TCs) are congenital brain malformations that protrude through skull defects and present as subcutaneous masses.

Cephaloceles contain variable combinations of brain/meninges/vessels. They vary in size from very large to small lesions ("atretic cephalocele").

Sinus pericranii is a compressible, bluish-tinged scalp mass that communicates with the intracranial venous system through a skull defect.