Cysts and Tumors of the Spleen

Cysts and tumors of the spleen are uncommonly encountered in clinical practice and continue to present challenges in both surgical work-up and treatment. Perhaps the continuing evolution of surgical traditions associated with splenic maladies can be partly explained by the relative rarity of these conditions. Literature references provide benchmarks to the myriad of supposed functions and attributes of the spleen as our experience and understanding of the organ continue to advance. For an excellent time line of medical and scientific inquiry into the function of the spleen, the reader is directed to the two-part review by McClusky et al. titled Tribute to a Triad: History of Splenic Anatomy, Physiology, and Surgery. Historically it has been questioned whether the spleen is required at all for survival. It was only within the latter half of the 20th century that the spleen came to be regarded as vital. For the majority of recorded history, the spleen, although often described as having diverse functions, was regarded as wholly unnecessary. This is reflected in early surgical approaches to splenic maladies. Although the veracity of these reports has been questioned, Adrian Zacarelli is thought to have performed the first splenectomy in 1549 on a 24-year-old woman who had developed splenomegaly. Later, Buliemi Ballonii (Ballonius) asked in a report of another splenectomy performed by an unknown barber-surgeon in 1578, “ Este igitur spelnatar necessarisu [Is the spleen so necessary for life]?” Ultimately, Edwin Beer would argue in 1928 that any splenic operation must be extirpative to be considered satisfactory.

Traumatic injury to the spleen provided the majority of the earliest opportunities to evaluate splenectomy as a successful treatment of splenic conditions. A testament to the rarity of splenic interventions is the observation that only 10 surgeons had followed in Zacarelli's footsteps during the next two and a half centuries. Almost invariably these reports concluded with success stories of patients returning to healthy lives. However, in 1826 Karl Quittenbaum performed an elective splenectomy on a 22-year-old female with splenomegaly, presumably from portal hypertension, that serves as the first recorded failure resulting in postoperative death. He was admonished for both his patient selection, given that the patient had ascites and anasarca, and his technique, in that a portion of the pancreas was found in the resected spleen. It was the author of those admonitions, Sir Thomas Spencer Wells, who would go on to note through his own failures that the spleen may have some necessary but as yet unknown hematologic role, and that an elective total splenectomy may only be appropriate for the treatment of life-threatening leukemia. He based these speculations on the observation that enlarged spleens were often found in conjunction with an abundance of leukocytes and that by removing the spleen the surgeon may cut off the production of these cells. His caution to those who would perform these procedures was in contrast to the long-held view of the nonnecessity of the organ. His hypothesis, although incorrect, was important to the beginning of applying methodology in evaluation of surgical treatments for conditions involving the spleen. A subsequent review of 49 splenectomies performed for the treatment of leukemia suggested an almost 90% mortality rate, and splenectomy as a treatment of choice for this condition would be later replaced by irradiation.

During the 20th century clinicians continued to question the prevailing view that the spleen was unimportant. By 1952 King had observed increased rates of infection in children who had undergone splenectomy. Recognition of the spleen's immunologic role and the description of overwhelming postsplenectomy infection (OPSI) encouraged surgeons to consider alternatives to extirpative surgery. Morgenstern and Shapiro are credited with the first successful open partial splenectomy for an epidermoid cyst in 1980. Continuing advances in minimally invasive surgery allowed Seshadri et al. to complete the first successful laparoscopic partial splenectomy in 2000. Advances in surgical technology have increased the number of management options for pathologic lesions of the spleen. Paralleled technologic improvements in radiologic imaging, along with an increase in abdominal imaging, have led to more frequent diagnosis of splenic abnormalities, especially cystic and solid lesions.

Approach to the Splenic Mass

As with any medical condition, a history and physical provide the basic foundation for the evaluation of the patient with a splenic lesion. Before one determines the most appropriate treatment, the nature or type of mass must be ascertained. Splenic masses are very rare when compared with masses involving other solid organs such as the ovary, liver, or kidney, so the physician may benefit from a simplified approach that assists in the correct diagnosis and timely treatment. Patients may present to the surgeon's office with classic complaints of left upper quadrant pain or otherwise vague abdominal discomfort; however, they are frequently asymptomatic with a mass incidentally discovered in imaging obtained for other purposes. Noninvasive radiographic imaging is necessary in assisting the initial classification of the lesion as cystic or solid as well as providing size measurements. Ultrasound (US) can demonstrate the internal echoes indicative of an abscess or hematoma versus the round homogeneous, anechoic enhancing signal that is the hallmark of a cystic structure. Computed tomography (CT) scanning with intravenous contrast or magnetic resonance imaging (MRI) can better delineate the trabeculated or septated nature of the cyst wall and wall calcification and has a superior specificity in defining whether a mass is cystic or solid. Cysts observed on CT typically demonstrate attenuation near water without rim enhancement. CT scanning may be especially useful when US views are limited by obesity or signal distortion from overlying bowel gas or the lower ribs.

Both cysts and solid tumors are further divided, each into two broad categories. A cyst is classified as either a primary (true) cyst containing an epithelial lining or, more commonly, a secondary cyst (pseudocyst), which lacks an epithelial lining. True cysts are either parasitic or nonparasitic, whereas pseudocysts most commonly arise as the result of blunt abdominal trauma. Tumors of the spleen are divided into either lymphoid or nonlymphoid types. Lymphoid tumors are mainly of the Hodgkin or non-Hodgkin variety. Nonlymphoid tumors, if primary, are most commonly of vascular origin and may be either benign or malignant. Secondary nonlymphoid tumors are metastatic. This broad schema may serve as a starting point to understand the etiology of the mass and thereby provide the most appropriate course of treatment without undue risk of immunologic complication to the patient ( Table 142.1 ).

TABLE 142.1

Classification of Splenic Masses

Solid Masses	Cystic Masses
LYMPHOID	PRIMARY OR “TRUE”
Hodgkin	Parasitic
Non-Hodgkin	Nonparasitic
NONLYMPHOID	Congenital
Benign	Neoplastic
Malignant (Primary or metastatic)	PSEUDOCYSTS
	Posttraumatic
	Other

Options for treatment include medical management with continued observation and/or surgical intervention. The varied types of intervention available include splenectomy, either complete or partial, percutaneous drainage, fenestration, or marsupialization. Management decisions will be based in part on the presentation of the patient but also by the etiology of the lesion.

Cystic Lesions

Splenic cysts are most common in the second and third decades of life, although they have been noted in all age groups including infants. An asymptomatic abdominal mass is the presenting feature in 30% to 45% of cases. Abdominal symptoms such as pain or physical examination findings may present in children and adults, but symptoms are more common when cysts are larger than 6 to 8 cm. Signs may arise from the compression on adjacent structures by an enlarging mass. For example, poorly controlled hypertension may arise because of compression of the left renal artery or vague urinary complaints caused by compression and/or pressure on the left kidney or ureteropelvic junction. The pain may either be localized or referred, classically to the left shoulder. A review of systems may yield complaints of gastrointestinal distress that are neither associated with meals nor helped by antacids. Respiratory complaints may include shortness of breath, pleuritic chest pain, or even a history of left lower lobe pneumonia. Sudden onset of abdominal pain and peritoneal signs caused by rupture may occur in previously asymptomatic patients, as the risk of rupture is 25% in cysts larger than 5 cm.

Fowler is credited with the first classification system for splenic cysts after reviewing more than 400 cases. There have been attempts to simplify his system, most recently by Hansen and Moller, who collectively reviewed 800 reported cases. It is important to note that the prevalence of primary versus secondary cysts differs in the United States versus other parts of the world, especially in areas endemic for Echinococcus , such as south central Europe, South America, and Australia. Worldwide (but not in the United States) the vast majority of primary or “true” splenic cysts are parasitic, two-thirds or more being caused by echinococci, with Echinococcus granulosus being the most common species. The echinococcal splenic cyst is composed of an inner germinal layer and an outer laminated layer surrounded by a fibrous capsule, characteristically multilocular in appearance and filled with fluid under pressure. It may contain daughter cysts and infective scolices. Echinococcal cysts may be asymptomatic or may cause pressure symptoms when they reach a large enough size, become secondarily infected, or rupture. Diagnosis is suggested by a history of travel to an endemic area and may be confirmed by indirect hemagglutination or enzyme-linked immunosorbent assay tests, which are positive in approximately 90% of patients with echinococcal cysts. Although hepatic hydatid cysts of echinococcal disease may be treated with percutaneous drainage and systemic treatment with albendazole, the treatment of choice for splenic hydatid cysts is splenectomy. However, there have been reports of limited success in small (<5 cm) single cysts with chemical sterilization with cetrimide, 3% sodium chloride, or ethanol and cyst evacuation to achieve splenic salvage. Whichever method is chosen, care must be taken to avoid intraperitoneal spillage and the resultant potential for anaphylaxis and hypotension. Low morbidity rates have been reported in patients needing to undergo simultaneous surgical treatment of splenic and hepatic hydatid cysts.

The remaining causes of nonparasitic primary cysts include congenital and neoplastic cysts. Congenital causes account for approximately 10% of all splenic cysts and 25% of nonparasitic cysts. Primary nonparasitic congenital cysts are seen predominantly in children and young adults. The developmental model proposed for these cysts suggests they arise as a result of invaginations of the mesothelium-lined splenic capsule and are primary in nature. Neoplastic nonparasitic cysts are much less common and historically have included epidermoid, dermoid, and endodermoid cysts, the latter being the most common. Endodermoid lesions are not true cysts and include lymphangiomas and hemangiomas; they are discussed later as solid masses. Dermoid cysts are exceedingly rare and are characterized by structures derived from all three germ layers, similar to a cystic teratoma. These lesions may be observed if they are small (<5 cm) and followed with US. Larger lesions should be surgically removed.

Three-quarters of nonparasitic splenic cysts are termed secondary cysts (pseudocysts) and are thought to be attributed to trauma, although 30% of these patients may not recall the specific event, suggesting that causes other than trauma (such as splenic infarcts or infection) may play a larger role than originally thought. Secondary cysts typically occur in young and middle-aged adults. Women are more affected than men, and the reasons for this are unknown, although hormonal effects and changes during pregnancy are presumed to play a role. Secondary cysts are thought to be formed by encapsulation of a splenic hematoma, subsequent absorption of the blood, and persistence of a false cyst wall. Clinically it is difficult to differentiate primary from secondary cysts, given the similarity of complaints, the overlap of the age groups, and the frequent omission of trauma from the patient's history. However, the treatment guidelines are also similar for primary and secondary cysts in that masses smaller than 5 cm may be observed and followed with serial US, whereas a surgical approach should be chosen for larger masses.

The tumor markers carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9) may be elevated in primary cysts, and studies have shown immunoreactivity of the cyst's inner lining to anti-CA 19-9. Because increased CEA or CA 19-9 levels may be from either benign or malignant processes, preoperative and postoperative levels documenting change are sometimes useful.

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