SUN-743 Elevated Alkaline Phosphatase as a Harbinger of Disseminated Carcinomatosis of the Bone Marrow: A Paget’s Disease Mimic

Abstract

Disclosure: S. Hoque: None. J. Upadhyay: None. G. Toraldo: None.

Background: Elevated alkaline phosphatase (ALP) often prompts consideration of conditions like Paget's disease and rare cancers. In such cases, it is crucial to rule out these possibilities. Disseminated carcinomatosis of the bone marrow (DCBM) is a rare and severe complication typically associated with poorly differentiated gastric cancer. It is caused by infiltration of bone marrow by cancer cells, leading to hematologic abnormalities such as disseminated intravascular coagulation and microangiopathic hemolytic anemia. DCBM has a poor prognosis with survival often limited to about one year, making its diagnosis critical. Case Description: A 59-year-old man with stage IV gastric signet ring carcinoma was referred for evaluation of Paget’s disease of bone. He presented with isolated elevated ALP, lumbar bone pain, compressive peripheral neuropathy, hearing loss, and tinnitus but no bone deformity, prior fracture, or heart failure. He was diagnosed with signet ring cell carcinoma two years prior and received neoadjuvant chemotherapy with 5-FLOT (5-fluorouracil, leucovorin, oxaliplatin, and docetaxel). An F18-FDG PET CT scan did not reveal metastatic disease though there was slightly increased tracer uptake in the gastric antrum. After partial laparoscopic gastrectomy, surgical pathology showed no significant tumor response to chemotherapy but did reveal lymphatic and vascular invasion, including metastases in the omental lymph nodes. The patient then underwent adjuvant chemotherapy with 5-FLOT. Repeat F18-FDG PET CT showed no metastatic disease. Over three months, the patient’s ALP increased from 68 U/L to 302 U/L (ref: 30-115 U/L). Bone-specific ALP was elevated while liver-specific ALP was not. CTX was 799 pg/mL (ref: 87-345 pg/mL). Complete blood count was normal except for mild anemia. There was no hypercalcemia or hyperbilirubinemia. A 99m-TcMDP bone scan had a superscan appearance with diffuse uptake in the axial skeleton. Spine MRI showed a diffusely heterogeneous background bone marrow signal, raising suspicion for a marrow replacing process. An iliac crest bone marrow biopsy confirmed metastatic carcinoma with signet ring cell features consistent with DCBM associated with the known primary gastric malignancy. Discussion: This case highlights the need to have a high degree of suspicion for DCBM in patients with poorly differentiated gastric cancer and rising ALP. The rapid increase in ALP argued against a coexisting diagnosis of Paget's disease of bone. DCBM primarily involves the axial skeleton and can present years after surgical resection of gastric cancer. While our patient did not have multiple cytopenias or evidence of metastatic disease on F18-FDG PET CT, the superscan appearance on the bone scan was pivotal. This spurred an expedited workup with bone marrow biopsy. Prompt diagnosis of DCBM is essential due to the poor prognosis associated with this condition.

Presentation: Sunday, July 13, 2025