To the authors' knowledge, the prognostic significance of plasma cell cytology in soft tissue (ST) masses from patients with multiple myeloma (MM) is unknown. Myeloma patients usually are monitored by bone marrow (BM) aspirates and biopsies to assess plasma cell differentiation, tumor burden, and response to treatment. Monitoring of ST lesions by fine-needle aspiration (FNA) is not performed routinely. The objective of the current study was to examine ST masses in MM patients using FNA and to classify and determine the prognostic significance of MM in these lesions based on cytologic features.
FNAs of 30 ST masses from 27 patients with a history of MM were examined for disease involvement. In the patients with MM, the cytologic features were evaluated and the lesions were graded as low grade, intermediate grade, or high grade based on the classification of Bartl et al. for MM in BM specimens. Concurrent BM samples as well as cytogenetic and flow cytometric results also were reviewed.
Twenty-seven of the FNA specimens (90%) were positive for MM, and three specimens (10%) were negative (one case each of lipoma, keratinous cyst, and aspergillosis). Among the MM cases, 5 (18.5%) were low grade, 15 (55.6%) were intermediate grade, and 7 (25.9%) were high grade (blastic MM). Simultaneous BM involvement was present in 23.5% of low-grade MM (4 of 17 cases), 35.3% of intermediate-grade MM (6 of 17 cases), and 71% of high-grade MM (5 of 7 cases). Clinically, 10 of 24 patients (42%) died within 9 months (median, 2 months). Patients with high-grade myeloma (blastic MM) in ST masses appeared to have worse survival; 43% (3 of 7 patients) died by a median time of 2 months, compared with 12% of patients with low-grade and intermediate-grade MM (2 of 17 patients).
FNA of ST masses appears to improve the management of MM patients by providing diagnostic material, samples for ancillary studies, and prognostic information. ST MM can be classified reliably into grades of prognostic significance utilizing the classification of Bartl et al. Intermediate-grade MM was the most frequent subtype present in ST masses.