“ Splenic lesions are commonly encountered and are often incidental in nature. Benign splenic vascular neoplasms include hemangioma, hamartoma, lymphangioma, extra-medullary hematopoiesis (EMH), and sclerosing angiomatoid nodular transformation (SANT). Uncommonly encountered entities of the spleen include focal EMH, focal myeloma, angiomyolipoma, and SANT. Primary splenic angiosarcoma is the most common malignant nonhematolymphoid malignancy of the spleen. Lymphoma, myeloma, and metastases are the other malignant entities involving the spleen.” 
Nonneoplastic, benign, and malignant splenic diseases: cross-sectional imaging findings and rare disease entities.
Thipphavong S et al.
AJR Am J Roentgenol. 2014 Aug;203(2):315-22

“Congenital cysts (i.e., epithelial cysts, epidermoid cysts) of the spleen are cysts lined with epithelial cells. These cysts are thought to present as either mesothelial cysts or cysts with squamous metaplasia within preexisting mesothelial cysts, arising from embryonic inclusions of the surface mesothelium in the developing spleen. They usually present in patients without symptoms and are found incidentally on imaging.” 
Nonneoplastic, benign, and malignant splenic diseases: cross-sectional imaging findings and rare disease entities.
Thipphavong S et al.
AJR Am J Roentgenol. 2014 Aug;203(2):315-22

“Splenic hemangiomas are the most frequently occurring benign tumor of the spleen, with a rate of occurrence in autopsy series of 0.03–14% . Splenic hemangiomas are thought to be congenital in origin, arising from sinusoidal epithelium, and most are the cavernous type. Most hemangiomas are small (reported size range, 0.5–7.0 cm) , incidental, and asymptomatic.” 
Nonneoplastic, benign, and malignant splenic diseases: cross-sectional imaging findings and rare disease entities.
Thipphavong S et al.
AJR Am J Roentgenol. 2014 Aug;203(2):315-22

“Splenic hamartomas are tumors composed of a varying mixture of tumor tissue and normal splenic tissue, with reported sizes ranging from 0.3 to 20.0 cm. Hamartomas are solid lesions that may contain a cystic or necrotic component. Splenic hamartomas can be associated with syndromes—namely, tuberous sclerosis and Wiskott-Aldrich- syndrome. Two subtypes of splenic hamartomas can occur: white pulp lesions, which are composed of aberrant lymphoid tissue, and red pulp lesions, which are composed of an aberrant complex of sinuses. Most hamartomas are a mixture of the two subtypes.” 
Nonneoplastic, benign, and malignant splenic diseases: cross-sectional imaging findings and rare disease entities.
Thipphavong S et al.
AJR Am J Roentgenol. 2014 Aug;203(2):315-22

Purpose: To evaluate whether an incidentally noted splenic mass at abdominal computed tomography (CT) requires further imaging work-up. 
Conclusion: In an incidental splenic mass, the likelihood of malignancy is very low (1.0%). Therefore, follow-up of incidental splenic masses may not be indicated. 
The Incidental Splenic Mass at CT: Does It Need Further Work-up? An Observational Study 
Siewert B et al.
Radiology 2018; 287:156–166

“Follow-up of splenic masses inci- dentally detected at CT (i.e., in patients with no evidence of previous or newly diagnosed malignancy and no systemic symptoms or localized pain) does not appear to be indicated.”
The Incidental Splenic Mass at CT: Does It Need Further Work-up? An Observational Study 
Siewert B et al.
Radiology 2018; 287:156–166

“This study included 379 patients, 214 (56.5%) women and 165 (43.5%) men, with a mean age 6 standard deviation of 59.3 years 6 15.3 (range, 21–97 years). There were 145 (38.3%) patients in the malignancy group, 29 (7.6%) patients in the symptomatic group, and 205 (54.1%) patients in the incidental group. The incidence of malignant splenic masses was 49 of 145 (33.8%) in the malignancy group, eight of 29 (27.6%) in the symptomatic group, and two of 205 (1.0%) in the incidental group (P , .0001). The incidental group consisted of new diagnoses of lymphoma in one (50%) patient and metastases from ovarian carcinoma in one (50%) patient. Malignant splenic masses in the incidental group were not indeterminate, because synchronous tumors in other organs were diagnostic of malignancy.”
The Incidental Splenic Mass at CT: Does It Need Further Work-up? An Observational Study 
Siewert B et al.
Radiology 2018; 287:156–166

“In conclusion, in patients with an incidental splenic mass identified at imaging and with the absence of a history of malignancy, fever, weight loss, or pain in the left upper quadrant or epigastrium, such masses are highly likely to be benign regardless of their appear- ance. Additional imaging or follow-up is not warranted, even if the mass does not show the appearance of a simple cyst. Further work-up is only needed if the splenic mass is seen in conjunction with other findings worrisome for malignancy.”
The Incidental Splenic Mass at CT: Does It Need Further Work-up? An Observational Study 
Siewert B et al.
Radiology 2018; 287:156–166

CT appearance

• may enhance similar to hepatic hemangiomas
• may remain hypodense or hyperdense
• may have calcifications
• Can appear solid or cystic

Spleen

• Up to 59% of patients with sarcoidosis have splenic involvement
• CT findings range from splenomegaly, to solitary nodules to multiple nodules

Splenic Abscess

• relatively rare, but potentially fatal
• risk factors
  • diabetes, alcoholism, IVDA