ML-11 DETECTION OF MYD88 MUTATIONS FROM CELL FREE DNA AIDS IN THE DIAGNOSIS OF CENTRAL NERVOUS SYSTEM LYMPHOMAS

BACKGROUND: Diagnosis of primary central nervous system lymphomas (PCNSL) can be challenging. We have shown that the detection of MYD88 mutation in cell free DNA (cfDNA) taken from cerebrospinal fluid (CSF) is reliable (JCO Precision Oncology, 2019; Leukemia and Lymphoma, 2019). We report four cases in which detection of MYD88 mutation aided in the diagnosis. CASE 1: A 67-year-old man with a history of systemic B-cell lymphoma, experienced right hemiparesis. MRI showed a slightly enhancing lesion located in the midbrain. MYD88 L265P mutation was found by digital droplet PCR analysis of cfDNA extracted from CSF. The patient underwent a needle biopsy, and was diagnosed as diffuse large B-cell lymphoma. CASE 2: A 32-year-old man was diagnosed as having a demyelinating lesion after experiencing severe headaches. A small enhancing lesion was found in the right frontal lobe, and the patient was treated with steroids. The lesions repeatedly disappeared and reappeared and finally, stopped responding to steroids. MYD88 mutation was detected. A biopsy was performed, and the diagnosis was PCNSL. CASE 3: A 49-year-old man underwent a biopsy for a right frontal lesion after experiencing memory loss; the pathology showed broad T-cell infiltration but only some perivascular B-cells with slight atypia. The patient was tapered off steroids, and the lesion spread rapidly. An open biopsy was performed, but the pathology was not typical for B-cell lymphoma. The patient’s symptoms rapidly worsened, and whole brain irradiation was performed. At recurrence, MYD88 mutation was detected. CASE 4: An 82-year-old man presented with blurred vision. Vitreous humor biopsy was inconclusive for ocular lymphoma. A head MRI showed an intracranial lesion which spontaneously regressed. MYD88 was detected, and the patient is being closely observed. CONCLUSION: Detection of MYD88 mutation from cfDNA extracted from CSF can aid in the diagnosis of CNS lymphoma, especially in atypical cases.