Isolated splenic metastasis: An unusual presentation of colonic adenocarcinoma

It is very uncommon situation in which primary colonic carcinoma is asymptomatic and presents as isolated splenic metastasis. Involvement of spleen by secondary tumors is usually seen in disseminated spread of tumor. However, isolated splenic involvement by tumor metastasis is an infrequent event, except in cases of lymphoid origin malignancy where spleen is commonly involved. We hereby report a case of 50 years old man who presented with gradually increasing pain abdomen for 3 months. USG report showed splenomegaly indicating either splenic abscess or hemangioma. Splenectomy was performed followed by pathological examination. Histopathological examination (HPE) revealed diffuse infi ltration of spleen by sheets and nests of malignant cells, suggesting metastatic adenocarcinoma to spleen. Subsequently computed tomography was done to fi nd out the site of primary tumor. Thus a cystic mass in left splenic fl exure of colon was identifi ed on CT scan. Biopsy was done that suggested colonic cancer. Hence a diagnosis of colonic mucinous adenocarcinoma with metastatic splenic involvement was made. Patient was operated for the same and managed accordingly. Based on this case, we concluded that surgeons should pay careful attention to splenic lesions as metastatic deposits can be there, especially in old aged patients having features that favor some ongoing malignant disease. Case Report Isolated splenic metastasis: An unusual presentation of colonic adenocarcinoma Mohsin Aijaz1*, Mahboob Hasan2 and Feroz Alam3 1Senior Resident, Department of Pathology, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh 202002 U.P, India 2Professor, Department of Pathology, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh 202002 U.P, India 3Assistant Professor, Department of Pathology, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh 202002 U.P, India Received: 12 August, 2019 Accepted: 23 August, 2019 Published: 24 August, 2019 *Corresponding author: Mohsin Aijaz, Senior Resident, Department of Pathology, Jawaharlal Nehru Medical College, Aligarh Muslim University, Aligarh 202002 U.P, India, E-mail:


Introduction
Spleen is a very unusual site of metastatic tumor spread. This is based on various anatomical, histological and functional features of the spleen, that make it impervious for secondary tumors [1]. Majority of the cases are part of disseminated metastatic diseases and usually arise from breast, ovary, lung, gastric, colorectal cancer and skin melanoma [2].

Case Report
We report a rare case of 50 years old male patient who visited surgical outpatient department of JNMCH, AMU Aligarh with chief complaint of pain in left upper abdomen for 3 months. Pain was localized to left hypochondrium and was dull aching, non-colicky and non-radiating, with gradual increase in its intensity. For last 20 days, pain was so much severe that it hampered his routine activities. It was not associated with vomiting or diarrhea. No history of malena, hematemesis or hematuria was there. No history of alcohol intake was there but the patient was a chronic smoker. Patient also gave history of weight loss and decreased appetite for the same duration. malaria was done that also exhibited negative fi ndings. Further ultrasonography of abdomen was done that revealed a welldefi ned heterogenous hypoechoic lesion in left supra renal fossa along with splenomegaly. Provisional diagnosis of splenic abscess or haemangioma was made. Subsequently splenectomy was done followed by histopathological examination.
Gross examination showed splenic enlargement with a dimension of 14 x 10 x 4 cms. Splenic capsule showed strong adherence with perisplenic fats. Cut section showed white homogenous area with specks of haemorrhage ( Figure 1). Results of histopathology were very surprising and showed sheets, nests and island of mucin containing malignant cells often forming glands, infi ltrating throughout the spleen and also in the attached perisplenic fats ( Figure 2). Thus the diagnosis of adenocarcinoma metastatic to spleen was made. Immunohistochemistry (IHC) was applied as a useful ancillary adjunct to morphologic examination for determining site of origin for adenocarcinoma. Cytokeratin staining is helpful in the diagnostic differentiation of metastatic lesions and assists in determining the site of origin from two common primaries (lung and colon). Hence Cytokeratin 7 and 20 was applied. CK7 was found to be negative in tumor cells (ruling out lung, upper gastrointestinal tract adenocarcinomas and many other adenocarcinomas). However, Cytokeratin 20 was found to be positive in tumor cells (seen in colonic adenocarcinoma). Keeping in view the suspected metastasis from colon, further CDX2 and p53 were applied that also showed strong positive nuclear staining in tumor cells, thus adhering us to diagnosis of metastasis from colonic carcinoma ( Figure 3). Post operatively CT Scan was advised to confi rm the primary site. This case also has similar presentation and hence highlights the importance of spleen as one of the rare site of metastatic tumor, that too in the absence of clinical suspicion.

Discussion
Spleen is one of the such visceral organ where isolated metastasis is very rare. The anatomical, histological or physiological features of spleen makes it an unusual site for tumor secondaries [1]. A number of hypotheses have been laid down by various authors. According to Sappington, there is sharp angle of the splenic artery with celiac axis that is associated with low incidence of splenic metastasis [3]. whereas Kettle suggested the role of rhythmic contraction of the spleen that might prevent growth of tumor emboli there [4]. It has been seen that even if the neoplastic cells reach the spleen, growth of tumor cells is opposed by splenic microenvironment. This is partly attributed to production of a humoral factor, the splenic factor that avoids tumoral cells adhesion and trigger their cytolysis [5]. Being a reticuloendothelial organ, phagocytic activity has also been suggested as possible factors preventing malignant cells development in the spleen [6].
Both haematological and lymphatic pathways have been supposed to be the channels for metastatic spread. But unlike other visceral organs, the splenic parenchyma lacks afferent lymphatic vessels. However lymphatic channels present in capsular and subcapsular regions can convey subcapsular splenic metastasis [7]. Many authors have the view that vascular route is the major pathway because the metastasis is usually limited to splenic parenchyma.
Various studies show that nearly 7% of cancer autopsies have metastasis to the spleen [8]. This usually seen in disseminated cancers. Isolated splenic metastasis is a rare event. Lung, endometrium, ovary, cervix, stomach, colon, melanoma, breast and bladder are the most common solid tumors in which splenic metastasis occurs [2]. Few cases of splenic metastases have also been reported from prostate, salivary gland and esophageal carcinomas [8,9].
Colorectal carcinoma usually metastasizes to regional lymph node, peritoneum and liver [10].  [13], as was also observed in our patient (184 ng/mL). CEA has been supposed to modulates the immune response and suppresses the humoral response as well as lymphocyte and NK cell activity [14]. It provides adhesion between cancer cells and macrophages, thus playing a signifi cant role in the pathogenesis of isolated splenic tumor metastasis [15].
Surgery is the primary modality of treatment followed by chemotherapy with or without radiotherapy in metastatic colorectal carcinoma. Our patient also underwent left hemicolectomy followed by chemotherapy (5-FU, leucovorine and oxaliplatin). Majority of cases in literature show a disease free survival period of 3-144 months after the diagnosis of primary tumor [16,17]. Whereas survival after splenectomy in metachronous involvement varies between 6 months to 7 years [18]. So, prognosis of isolated splenic colorectal metastasis is more favorable, although these cases show distant metastatic spread.

Conclusion
Spleen is an uncommon site of metastatic tumor spread.
Any splenic mass in an asymptomatic patient is usually o Phagocytic activity has also been suggested as possible factors preventing malignant cells development in the spleen.