"Sneaky Spleen": Three Cases of Ectopic Splenic Tissue Mimicking Neoplasia

Abstract

Ectopic splenic tissue may arise as either a congenital anomaly or acquired seeding of fragments from a mechanically disrupted spleen. Regardless of the etiology, splenic tissue presenting at unexpected sites may lead to symptomatic or incidentally discovered lesions that may raise clinical suspicion for neoplasia. We present three cases of ectopic splenic tissue that were clinically ominous and necessitated pathologic tissue examination for definitive diagnosis.

Keywords: accessory spleen; case report; splenosis.

Figure 1

Case 1 microscopic findings, hematoxylin and eosin–stained slides. (a) Low magnification revealed a well-circumscribed mass with a thick fibrous capsule (yellow arrow) that was sharply demarcated from the adjacent adipose tissue (orange arrow) (2x). (b) Beneath the fibrous capsule (yellow arrow), the mass was composed of white pulp and red pulp characteristic of splenic tissue (4x). (c) Scattered lymphoid follicles (white arrow) and periarteriolar lymphatic sheath (blue arrow), comprising the white pulp compartment, were admixed with red pulp (10x). (d) Higher optical magnification of the white pulp showed an activated follicle composed of a germinal center (green arrow) surrounded by a dense rim of small lymphocytes representing the mantle zone (yellow arrow) and a more expanded rim of lymphocytes representing the marginal zone (red arrow) (20x). (e) Periarteriolar lymphatic sheath, consisting of mature lymphocytes (blue arrow) adjacent to arterioles (red arrow), was also identified (20x). (f) The red pulp was composed of a network of capillaries, venous sinuses (orange arrows) lined by cuboidal cells, and splenic cords (tissue between the sinuses) (40x).

Figure 2

Case 2 radiographic findings. CT abdomen and pelvis (coronal view) showed multiple soft tissue lesions throughout the (a, b) omentum and (c, d) pelvic peritoneum, the largest located anterior to the bladder and measuring 2.5 cm.

Figure 3

Case 2 microscopic findings, hematoxylin and eosin–stained slides. (a, b) Both peritoneal biopsies showed a well-circumscribed, encapsulated nodule within fibroadipose tissue (4x and 10x, respectively). (c) Higher optical magnification (20x) revealed that the nodules were composed of a fibrous capsule (yellow arrow), mature-appearing lymphocytes (white arrow), and splenic cords and sinuses (red arrow).

Figure 4

Case 3 radiographic findings. CT abdomen and pelvis with contrast showed a 1.2-cm arterial enhancing mass in the pancreatic tail (arrow). There was no pancreatic ductal dilatation, and the remainder of the pancreas showed normal enhancement.

Figure 5

Case 3 gross and microscopic findings. (a) Cut section from the gross specimen showed a 1.5-cm well-circumscribed red-purple mass within the pancreatic parenchyma. (b) Histologic examination of hematoxylin and eosin–stained slides revealed splenic tissue (blue arrow) sharply demarcated from the pancreatic parenchyma (white arrow) by a fibrous capsule (yellow arrow) (4x). (c) Focally, the pancreatic parenchyma adjacent to the splenule showed fibrosis and loss of acinar tissue consistent with chronic pancreatitis (red arrows), while the remaining pancreatic tissue showed normal microanatomy (white arrow) (10x). The splenule consisted of (d) red pulp (20x), (e) scattered lymphoid follicles (green arrow) (20x), and (f) collections of mature lymphocytes adjacent to arterioles (orange arrows) consistent with periarteriolar lymphatic sheaths (20x).