Alveolar rhabdomyosarcomas involving serous cavity fluid specimens exhibit diverse cytomorphologies: A case report and review of the literature

Abstract

Involvement of serous cavity specimens by alveolar rhabdomyosarcoma (ARMS) is a rare event and only a few case reports have been reported in the literature, with conflicting cytomorphologic patterns. Herein, we report on a 41-year-old man with no significant past medical history who presented with pancytopenia and shortness of breath and was found to have widely metastatic sinonasal alveolar rhabdomyosarcoma, including involvement of the pleura. The pleural fluid specimen was cellular and contained ARMS cells in small-to-medium sized three-dimensional fragments that resembled an adenocarcinoma or mesothelioma, and numerous single cells were seen in the background. The individual tumor cells demonstrated variable morphology; all were large, with varying degree of cytoplasm, and multinucleated cells were commonly seen in the background. The cells were negative for calretinin and claudin-4 and were positive for myogenin, confirming the diagnosis. Given the cytomorphologic diversity of ARMS seen in serous fluid specimens, patient history and the use of confirmatory immunostains are essential.

A Review of Effusion Cytomorphology of Small Round Cell Tumors

“…Another diagnostic pitfall is described by Jones and VandenBussche [43] whereby fragments of 3-dimensional alveolar RMS (ARMS) tumor clusters in the cell block show prominent retraction artifact, mimicking adenocarcinoma (Fig. 1a–d).…”

“…These large cells have a rhabdoid morphology with eccentrically placed nuclei, irregular nuclear contours, coarse chromatin, occasional prominent nucleoli, conspicuous perinuclear clearing, and abundant dense cytoplasm with occasional condensed intracytoplasmic globules [1, 4, 7, 10, 39, 40, 43]. Multinucleated giant cells with “wreath-like” nuclear arrangements and intranuclear inclusions are occasionally seen [7, 37, 40, 43]. Strap cells or cells with cytoplasmic cross-striations have not been described in effusion samples [7, 39].…”

“…Effusion samples involving RMS are rare but have been described in various studies involving peritoneal, pleural, and cerebral spinal fluids [1,4,7,10,[39][40][41][42][43]. The cellularity ranges from scattered singly dispersed cells to abundant loosely cohesive tumor cell clusters in a back- ground of occasional karyorrhexis, proteinaceous debris, reactive mesothelial cells, and inflammation [1,4,37,39,40,43]. Cytomorphologically, there is a spectrum of small round cells and pleomorphic large cells [1,39,40].…”

“…1a-d). These malignant cells have pale to eosinophilic, vacuolated cytoplasm which further resembles glandular differentiation [43]. IHC stains are helpful in differentiating epithelial from rhabdomyoblastic differentiation.…”

“…The authors also reported the cytomorphologic variability within the same specimen, an unusual finding for a translocation sarcoma which often shows monomorphic tumor cells. Clinical history and ancillary studies are helpful to overcome this diagnostic challenge [43].…”