Intravitam diagnosis of splenic lymphoma in three horses

Introduction. Lymphoma represents the 00.2-5% of all equine neoplasms and is classified as multicentric, alimentary, mediastinal and cutaneous. Occasionally, solitary solid tumors may involve the spleen. Equine splenic lymphoma tends to progressively involve adjacent abdominal organs with only late metastatic spread and no bone marrow involvement. Early intra-vitam diagnosis may represent a key factor in attempting radical treatments, such as splenectomy. Difficulties in early diagnosis are related to the non-specific clinical presentation; furthermore, the patient size prevents the use of imaging techniques normally used to investigate suspicious human or small animal patients. In most cases, equine lymphoma is not recognized intra-vitam and a definitive diagnosis is achieved only post-mortem. Suspicion of lymphoma and early diagnosis may be achieved observing clinical signs and establishing a standardized approach including specific clinical, imaging and laboratory procedures. In the present study, successful intra-vitam diagnostic approach in three cases of splenic lymphoma is reported; besides, definition of clinical findings and diagnostic tools to be considered as essential to achieve an early intra-vitam diagnosis will be discussed. Description of the case. A 3 y.o. Arabian mare (case 1), a 3 y.o. Paint gelding (case 2) and a 6 y.o. KWPN mare (case 3) were referred for severe chronic wasting and recurrent hyperthermia. Polyuria/polydipsia was reported for cases 1 and 2. On admission, tachycardia was detected (52, 89, 46 bpm respectively); increased rectal temperature (38.8°C) was recorded in case 3. Clinical pathology showed hypocromic anemia (Hb=12.9; 8; 9.7 g/dl respectively), leukocytosis (case 1 WBC=13460/mm3; case 2 WBC= 11480/mm3) or leucopenia (case 3 WBC= 3780/mm3) with relative monocytosis (8, 8, 12.3% respectively), increased serum LDH (case 1 620 U/l and case 2 807 U/l) and lipases (case 1 276 U/l and case 3 88 U/l). In all cases abdominal ultrasonography revealed the presence of a mass placed in the left hypochondrium involving the spleen, with no evident delimitation. The mass showed mixed echogenicity, fluid-filled anahecoic concamerated portions and marked neo-vascularization. Peritoneal fluid cytology revealed increased macrophagic phagocytic activity (especially leukophagocytosis and erithrocytosis), several clusters of reactive mesothelial cells and lymphoid-like cells with high mitotic rate, basophilic cytoplasm and prominent nucleoli. Ultrasonographic and peritoneal cytologic findings were suggestive of a solid lymphoid neoplasm involving the spleen; the involvement of other abdominal organs could not be ruled out. Necropsy was performed in cases 1 and 2, confirming the intra-vitam diagnosis of splenic lymphoma. A whitish cerebroid-like mass uniformly composed of neoplastic rounded lymphoid-like cells with multiple necrotic-calcified foci was detected within splenic parenchyma. Mesenteric lymphomegaly and diffuse sub-endocardial mineralization were also observed. Conclusions. Recurrent hyperthermia, chronic wasting and polyuria/polydipsia were considered non-specific clinical signs related to paraneoplastic syndromes such as negative energetic balance, tumor necrosis secondary inflammation and pseudohyperparathyroidism. Particularly, the latter, supported by sub-endocardial metastatic calcification, was previously reported only in equine multicentric and splenic lymphoma. Anemia could be immunomediated, related to hypersplenism or to consumption, while alteration in WBC were variable and it could reflect secondary inflammation and/or the immune response against the tumor. Interestingly, we detected increased serum levels of LDH that is commonly monitored as a prognostic factor in human oncology; this finding possibly represents an increase in erythrocyte isoform due to hypersplenism and massive hemocatheresis. In human lymphoma, lipase increase reflects pancreatitis related to pancreas neoplastic involvement or to pseudohyperparathyroidism; this could be true also for the cases presented here. Abdominal ultrasonography and abdominocentesis represented the key investigation techniques for the intravitam diagnosis of splenic lymphoma since their combination allowed both to identify the location and to classify the neoplasm. Peritoneal fluid cytology appears sensitive for the diagnosis of splenic lymphoma, particularly when compared to other abdominal neoplasms. Although ultrasonography and cytology do not allow a detailed definition of the lymphoma, they may be essential in equine practice where more complete imaging or biopsy techniques are invasive or not easily available. In our opinion, the clinical approach to any equine patient presented for recurrent hyperthermia, chronic wasting and polyuria/polydipsia should always consider equine lymphoma as differential diagnosis, and ultrasonography and peritoneal cytology should be sistematically included in the diagnostic protocol.