Objective To explore the clinicopathological features and differential diagnosis of pleomorphic rhabdomyosarcoma (PRMS).

Methods The clinical manifestations, pathological features, immunophenotypes and treatment of PRMS patients admitted to the First Affiliated Hospital of Soochow University from June 2008 to March 2023 were retrospectively collected. The survival status of the patients and whether they had local recurrence or metastasis were obtained by telephone follow-up.

Results A total of 6 patients with PRMS were included, including 5 males and 1 female, aged from 29 to 77 years old, with an average age of 54.17 years. The sites of sarcoma were right upper arm, right renal pelvis, left sinus/neck/lower mandible, right shoulder and back, right gluteus maximus and nasopharynx, respectively. Of the 4 patients with complete clinical data, 1 showed blood in the nose and abnormal sensation in the throat, 3 showed progressive enlargement of the mass, and 2 of them were accompanied by tenderness. Imaging of 4 patients showed space-occupying lesions. Histologically, 3 cases (50%) showed coagulative necrosis, 4 cases (66.7%) showed typical pleomorphic sarcoma, and 2 cases (33.3%) were mainly atypical spindle cell. Immunohistochemical staining showed that 6 cases (100%) had diffuse expression of desmin, and focal expression of myogenin (5 cases 83.3%), MyoD1 (4 cases 66.7%) and SMA (1 case 16.7%) were found. The proliferation index of Ki-67 was 30%-70%. All 6 patients received surgical treatment, and complete follow-up data were obtained from 4 patients, all of whom received postoperative radiotherapy and/or chemotherapy, and died after recurrence or metastasis.

Conclusions As a rare type of RMS, PRMS has a high degree of malignancy and poor prognosis, so differential diagnosis is particularly important, but there is still no effective treatment.