Greipp, Patricia T.

Abstract Objectives Fluorescence in situ hybridization (FISH) for plasma cell neoplasms (PCNs) requires plasma cell (PC) identification or purification strategies to optimize results. We compared the efficacy of cytoplasmic immunoglobulin FISH (cIg-FISH) and fluorescence-activated cell sorting FISH (FACS-FISH) in a clinical laboratory setting. Methods The FISH analysis results of 14,855 samples from individuals with a suspected PCN subjected to cytogenetic evaluation between 2019 and 2022 with cIg-FISH (n = 6917) or FACS-FISH (n = 7938) testing were analyzed. Results Fluorescence-activated cell sorting–FISH increased the detection rate of abnormalities in comparison with cIg-FISH, with abnormal results documented in 54% vs 50% of cases, respectively (P < .001). It improved the detection of IGH::CCND1 (P < .001), IGH::MAF (P < .001), IGH::MAFB (P < .001), other IGH rearrangements (P < .001), and gains/amplifications of 1q (P < .001), whereas the detection rates of IGH::FGFR3 fusions (P = .3), loss of 17p (P = .3), and other abnormalities, including hyperdiploidy (P = .5), were similar. Insufficient PC yield for FISH analysis was decreased between cIg-FISH and FACS-FISH (22% and 3% respectively, P < .001). Flow cytometry allowed establishment of ploidy status in 91% of cases. In addition, FACS-FISH decreased analysis times, workload efforts, and operating costs. Conclusions Fluorescence-activated cell sorting–FISH is an efficient PC purification strategy that affords significant improvement in diagnostic yield and decreases workflow requirements in comparison with cIg-FISH.

Context.— Unlike B-cell acute lymphoblastic leukemia/lymphoma (ALL/LBL), there have been few therapeutic advances in T-cell ALL (T-ALL)/LBL, an aggressive ALL/LBL subtype. Objective.— To perform a focused tissue array study to elucidate tumor markers of therapeutic potential in T-ALL/LBL. Design.— Using immunohistochemistry, we evaluated expression of leukemic antigens of interest, specifically CC-chemokine receptor 4 (CCR4), among others, on available remnant diagnostic material, including tumor tissue slides obtained from formalin-fixed, paraffin-embedded preserved tissues. Results.— Our analysis identified, for the first time, expression of CCR4 in T-ALL/LBL in 11 of 27 cases (40.7%) and confirmed common expression of BCL2, CD38, and CD47, as reported previously. We also identified the expression of CD123 in 4 of 26 cases (15.4%), whereas BCL6 and PDL1 were expressed in a small number of T-ALL/LBL cases. The potential novel target CCR4 was significantly more common in the Pre/Pro-T immunophenotypic subtype, 6 of 9 (66.7%, P = .01). No additional differences in clinical and epidemiologic variables were noted among positive or negative CCR4 cases. Conclusions.— These findings support preclinical and clinical testing of therapies targeting CCR4, CD47, BCL2, CD38, and CD123 in T-ALL/LBL, and may help guide the development of targeted clinical trials in T-ALL/LBL, a rare disease in urgent need of novel therapies.

Myxofibrosarcomas (MFS) present as slowly enlarging superficial masses in elderly patients. Even though these tumors fail to exhibit a distinct immunophenotype, diagnosis is straightforward when they present in subcutaneous tissue. Intramuscular MFS, however, are more challenging to diagnose as the differential also includes dedifferentiated liposarcoma with myxoid features. The vast majority of dedifferentiated liposarcomas show MDM2 amplification, whereas limited data exists as to the MDM2 status of MFS. We sought to explore the rate of MDM2 amplification in cases of classic MFS. Our archives were searched for MFS; only subcutaneous well-sampled resections were included. FISH for MDM2 amplification was performed on each tumor. A cohort of myxoid dedifferentiated liposarcoma resections was studied for comparison. Twenty-two MFS arose in patients aged 44 to 85 years. All tumors contained an infiltrative population of atypical cells embedded in a myxoid stroma with curvilinear blood vessels. MDM2 amplification by FISH was identified in 3 (of 22; 14%) tumors. Available follow up on 17 patients (range 1-96 months; median 13 months) revealed 6 patients with local recurrence and 1 with distant metastasis. Of 3 patients with MDM2- amplified MFS, 1 experienced recurrence and died of unrelated causes, while the second was alive without disease 12 months after diagnosis. Even though the rate of MDM2 amplification by FISH in MFS appears to be low, a subset of cases may show this genetic alteration, which pathologists should be aware of to avoid misclassification as myxoid dedifferentiated liposarcomas. Further studies are necessary to determine if amplification status adds prognostic value.

Abstract Most patients with solitary bone plasmacytomas (SBP) progress to multiple myeloma (MM) after definitive radiation therapy as their primary treatment. Whether the presence of high-risk (HR) cytogenetic abnormalities by fluorescence in situ hybridization (FISH) in the clonal plasma cells, obtained either directly from the diagnostic SBP tissue or the corresponding bone marrow examination at the time of diagnosis, is associated with a shorter time to progression (TTP) to MM is unknown. This study evaluated all patients diagnosed with SBP at the Mayo Clinic from January 2012 to July 2022. The presence of del(17p), t(14;16), t(4;14), or +1q (gain or amplification) by FISH in clonal plasma cells was defined as HR. A total of 114 patients were included in this cohort, and baseline FISH was available for 55 patients (48%), of which 22 were classified as HR (40%). The median TTP to MM for patients with SBP and HR FISH was 8 months (95% confidence interval [CI], 6.3-26) compared with 42 months (95% CI, 25-not reached [NR]) in patients with SBP without HR FISH (P < .001). In a multivariate analysis, only HR FISH was a significant predictor for shorter TTP to MM, independent of minimal marrow involvement and an abnormal serum free light chain ratio at diagnosis. Deletion (17p) and gain 1q abnormalities were the most common FISH abnormalities responsible for the short TTP to MM. Thus, assessing for HR FISH abnormalities in clonal plasma cells derived from either the diagnostic SBP tissue or the staging bone marrow examination of patients with newly diagnosed SBP is feasible and prognostic for a shorter TTP to MM.

TFEB-amplified renal cell carcinoma (RCC), which belongs to the MITF family of RCC, is characterized by genomic amplification at the 6p21.1 locus where the TFEB gene is located. The vascular endothelial growth factor A and cyclin D3 genes are also located at this same locus. When tumors lack classic morphologic features, they may be classified as “RCC not otherwise specified (NOS).” However, it is increasingly important to accurately diagnose the RCC subtype to define the patient's individual prognosis and select the subsequent therapeutic modalities, which now include targeted agents. Therefore, knowledge of the diagnostic features of TFEB-altered RCCs, such as t(6;11) RCCs and TFEB-amplified RCCs, is critical for identifying these tumors. Herein, we present an interesting case of TFEB-amplified RCC that was initially diagnosed as RCC NOS on biopsy of a renal tumor in a community practice setting with available molecular findings demonstrating CCND3 amplification. The genetic abnormality was “accidentally” detected due to the amplification of the colocated CCND3 gene at the 6p21 locus of the TFEB gene on a limited genetic sequencing panel. This case highlights the importance of molecular tests in accurately diagnosing RCC and carefully interpreting molecular findings in the context of histomorphologic features.