FLUID COLLECTIONS, CYSTS, AND HEMATOMAS
- There is great diversity in the appearance of fluid collections on computed tomography, magnetic resonance imaging, and ultrasound.
- Physical properties that interact with imaging parameters producing the diversity of these appearances is important to understand.
- Many cysts that are seen are clinically insignificant.
- Ultrasound is usually not definitive for diagnostic imaging purposes in evaluating cystic neck masses except for thyroid masses.
Tumor, infection, trauma (with or without bleeding and iatrogenic or by other mechanisms), and aberrant development (Chapter 8) can all be associated with cysts, localized fluid collections, and hematomas. Edema confined to a space can mimic a fluid collection.
Cysts, fluid collections, and bleeding occur very commonly in the sinuses. They are also common occurrences in the soft tissues and organ systems of the head and neck. They occur both within bone and beneath the periosteum. There are cysts associated with tumor and regressive cystic changes and bleeding within tumors or tumoral cysts and cystic tumors. Developmental cysts are common in the head and neck, and some, such as venolymphatic vascular malformations (Chapter 9), have bleeding as a complication.
GENERAL DIAGNOSTIC APPROACH
The general diagnostic approach to the evaluation of cysts, fluid collections, and hematomas or other collections of blood products includes consideration of one or more of the following topics.
The clinical setting virtually always guides the differential diagnosis. The origin and nature of a cyst, hematoma, or other fluid collection is usually not in question after imaging is combined with clinical data. Sampling by aspiration of fluid contents is usually not necessary unless cancer or infection is suspected. A partial list of some examples of common associated clinical circumstances follows:
- A history or acute setting of trauma raises the possibility of hematoma or posttraumatic hematocyst (Fig. 10.1).
- A rapid increase in size suggests bleeding or bleeding into a pre-existing lesion. (Fig. 10.2)
- A history of fluctuating size suggests a developmental lesion that may be liable to intermittent inflammation, one that may contain tissue responsive to inflammation, or one that communicates with the outside world somehow by a tract or fistula (Fig. 10.3).1,2
- Steady progressive enlargement over a protracted period of time without pain or signs of inflammation suggests a neoplasm (Fig. 10.4).1–3
- Fever, poor feeding, and pharyngitis with retropharyngeal edema in a young child suggest a suppurative retropharyngeal lymph node (Fig. 10.5).
Normal Variant and Common, or Incidental and Unimportant
Cysts or fluid collections are often anatomic variations such as the Tornwaldt cyst of the nasopharynx (Fig. 10.6).4 Cysts or fluid collections may also be totally innocuous, such as the very common postinflammatory cysts in the Waldeyer ring lymphoid tissue (Fig. 10.7) or simple mucous or retention cysts in the sinuses.1–3 Such variants should be recognized as unimportant clinically, but they do allow a study of the appearance of cyst contents in a way that might prove helpful in understanding cysts and fluid collections that do have some consequence.
Solitary or Multiple Cysts
If cysts or cystic masses are multiple, and especially if they are multiple and bilateral, they can suggest systemic diseases as diverse as basal cell nevus syndrome and HIV infection, depending on their anatomic distribution (Fig. 10.8). One the other hand, unilateral multiple parotid and periparotid cystic masses suggest a Warthin tumor or metastatic skin cancer to regional parotid nodes.
Multiple cystic lesions in the neck raise the possibility of lymphadenopathy.1–3 The pattern of disease and clinical situation usually clarify the likely etiology to no more than two choices (Fig. 10.9).
Decisions about whether a predominantly cystic mass is a nodal versus nonnodal etiology is largely driven by anatomy.
Developmental cysts such as those of the branchial apparatus (Figs. 10.10, 10.11 and 10.12) and thyroglossal duct (Figs. 10.13 and 10.14) often bear a characteristic relationship to the pharynx and other neck viscera, but some ambiguity in a purely anatomic differentiation arises in differentiation of second branchial cleft cysts and necrotic or otherwise cystic level 2A lymph nodes (Fig. 10.11).5–7
The sinonasal region, salivary glands, thyroid gland, and all other viscera have a tendency to be associated with certain types of cysts, fluid collections, and patterns of bleeding. For instance, serous and mucous retention cysts will be submucosal within the sinus cavity, and HIV-related epithelial cysts will be partially solid and usually bilateral in the parotid and sometimes submandibular glands (Fig. 10.8). Colloid cysts and cystic adenomas of the thyroid gland are ubiquitous, and some predominantly cystic masses may be thyroid cancer (Fig. 10.15).
Edema confined to a known anatomic space such as the retropharyngeal space may mimic a fluid collection.
Postoperative fluid collections in the low neck and supraclavicular fossa may be related to injury to the thoracic duct or other major lymphatic collecting trunks in this region (Fig. 10.16). Postoperative seromas typically accumulate in the anterior and/or posterior triangles and deep to the closure of the superficial fascia or deeper fascial layers of the neck after a surgical procedure, the most common being a neck dissection (Figs. 10.17–10.20).