Resolution of Regenerative Anemia, Thrombocytopenia, and Syncope After Cytoreduction of an Infiltrative Angiolipoma in a Dog: A Case Report

Angiolipomas are uncommon benign mesenchymal neoplasms composed of mature adipocytes and proliferating vascular channels. In dogs, infiltrative angiolipomas are rarely reported and have primarily been described as localized soft-tissue masses. An 11-year-old, 10.8 kg, castrated male Japanese Spitz was referred for evaluation of regenerative anemia, mild thrombocytopenia, recurrent syncopal episodes, and a 5-year history of a slowly enlarging ventral thoracic mass. Preoperative hematological evaluation demonstrated anemia with a hematocrit of 25.4% and an increased absolute reticulocyte count of 122.7 K/µL, supporting a regenerative erythropoietic response. The platelet count was mildly decreased at 109 × 103/µL. D-dimer concentration was increased (737.61 ng/mL; reference interval, 0–250 ng/mL), whereas prothrombin time (9.5 s; reference interval, 5–15 s) and activated partial thromboplastin time (15.6 s; reference interval, 15–45 s) were within their reference intervals. Referral history indicated that previous infectious and immune-mediated evaluations had not identified a definitive cause, although the original external testing records were unavailable for verification. Computed tomography revealed a heterogeneous subcutaneous mass with mixed fat- and soft-tissue-attenuating components, suspected infiltration of the superficial pectoral muscle, and focal rather than diffuse contrast enhancement. Surgical cytoreduction, including partial myectomy, was performed because complete excision was not considered feasible owing to deep muscular infiltration. Histopathological examination confirmed an infiltrative angiolipoma characterized by mature adipocytes, numerous vascular channels, skeletal muscle infiltration, and frequent intravascular fibrin thrombi. Following surgery, the hematological abnormalities progressively improved without blood transfusion or long-term immunosuppressive therapy. The platelet count increased from 109 × 103/µL preoperatively to 153 × 103/µL by postoperative day 16 and 202 × 103/µL by postoperative day 56. During the same period, the hematocrit increased from 25.4% to 45.0%, and the absolute reticulocyte count subsequently returned to the reference interval. The syncopal episodes ceased after surgery and did not recur during the available 12-month follow-up. Fibrinogen concentration and peripheral blood smear evaluation were unavailable, and serial postoperative coagulation testing was not performed. Accordingly, the temporal association between tumor cytoreduction and hematological improvement raises the possibility of a tumor-associated process, but neither the underlying mechanism nor a causal relationship could be established.