Case Presentation: A 75-year-old man with recurrent well-differentiated liposarcoma on Palbociclib s/p multiple tumor resections and recent cryoablation of a right retrocaval lesion 6 weeks prior, presented with 5 weeks of worsening right flank pain, decreased appetite, and 25-pound unintentional weight loss. He was afebrile with normal vitals. He had petechiae on his palate. Labs showed leukocytosis (28.3 x 10^9/mL; reference range [RR] 3.6-11.2 x 10^9); anemia; thrombocytopenia; elevated creatinine (1.97 mg/dL; RR 0.6-1.1 mg/dL), B12 (1,602 pg/mL; RR 211-911 pg/mL), AST (81 U/L; RR <=34 U/L), LDH (2,188 U/L; RR 120-246 U/L); hypoalbuminemia; urinalysis with >182 RBC / 127 WBC / rare bacteria. His CMP, haptoglobin, folate, reticulocyte count, PT, PTT, fibrinogen, and C3 complement were normal. Compared to 1-month prior, CT abdomen and pelvis showed a 1.2 cm non-obstructing right renal calculus and increase in size of a right retrocaval mass.Urology was consulted and felt that his right flank pain was from his retrocaval mass, not the large renal stone. He was admitted to the hospital. Hematology/oncology was consulted and Palbociclib was held, given possible association with thrombocytopenia [1]. Peripheral smear revealed few schistocytes as well as leukoerythroblastosis. Bone marrow biopsy showed dedifferentiated liposarcoma with heterologous rhabdomyosarcomatous differentiation, confirming liposarcoma bone marrow infiltration (Figures 1 and 2). Local progression of the primary malignancy and cryoablation were thought to be the cause his flank pain.During his stay, his pain was controlled, he received 1 unit of platelets, and was later discharged with oncology follow-up. Unfortunately, he was readmitted twice in the following 3 months with worsening leukocytosis attributed to aggressive liposarcoma progression. The patient and his family decided to proceed with comfort-based care, and he was transitioned to hospice; he passed 3 days later.

Discussion: Liposarcoma progression to the bone marrow is incredibly rare, documented in only a few cases. In one study, bone marrow infiltration was present in 7% of 74 adults with soft tissue sarcomas; only one case was a liposarcoma primary [2]. In 2001, Darvishian et al. detailed the case of a 55-year-old man with high-grade pleomorphic and lipoblastic liposarcoma with well-differentiated myxoid regions. Within roughly 15 months of his initial diagnosis, he was found to have pancytopenia with a left shift. Bone marrow biopsy showed complete marrow replacement by liposarcoma. Unfortunately, the patient died 3 weeks later from complications of his metastatic cancer [3]. In a patient with known liposarcoma with evidence of metastasis and local progression, careful monitoring for bone marrow involvement should be prioritized. A 2019 case report by Mehta et al documented the development of hyperleukocytosis as a paraneoplastic syndrome associated with dedifferentiated liposarcoma. Hyperleukocytosis in a patient with known liposarcoma may represent transformation before it has been formally detected [4]. These reports, along with our patient’s case, demonstrate the need for close monitoring and early bone marrow biopsy in this population.

Conclusions: Internists should recognize liposarcoma dedifferentiation and bone marrow infiltration as an incredibly rare event with poor prognosis that requires a high index of suspicion and a low threshold to pursue bone marrow biopsy monitoring.

IMAGE 1: Figure 1A (left): Bone marrow aspirate shows loosely cohesive aggregates of round blue cells, some in perivascular pattern. Figure 1B (right): The cells have inconspicuous nucleoli and increased mitotic activity. H&E stain 10X and 40X, respectively

IMAGE 2: Figure 2A (left), 2B (center), 2C (right): Positive MDM2 stain on bone marrow biopsy, positive desmin stain on bone marrow aspirate, and positive myogenin stain on bone marrow aspirate, respectively. H&E stain 4X, 10X, 10X, respectively.