Desmoplastic small round cell tumor: a rare cause of a progressive brachial plexopathy

Imaging of non-neurogenic peripheral nerve malignancy-a case series and systematic review

OBJECTIVE

To evaluate the frequency, clinico-pathologic and imaging features of malignant tumors in peripheral nerves which are of non-neurogenic origin (non-neurogenic peripheral nerve malignancy-PNM).

MATERIALS AND METHODS

We retrospectively reviewed our pathology database for malignant peripheral nerve tumors from 07/2014-07/2019 and performed a systematic review. Exclusion criteria were malignant peripheral nerve sheath tumor (MPNST). Clinico-pathologic and imaging features, apparent diffusion coefficient (ADC_min), and standard uptake values (SUV_max) are reported.

RESULTS

After exclusion of all neurogenic tumors (benign = 196, MPNST = 57), our search yielded 19 non-neurogenic PNMs (7%, n = 19/272), due to primary intraneural malignancy (16%, n = 3/19) and secondary perineural invasion from an adjacent malignancy (16%, n = 3/19) or metastatic disease (63%, n = 12/19). Non-neurogenic PNMs were located in the lumbosacral plexus/sciatic nerves (47%, n = 9/19), brachial plexus (32%, n = 6/19), femoral nerve (5%, n = 1/19), tibial nerve (5%, n = 1/19), ulnar nerve (5%, n = 1/19), and radial nerve (5%, n = 1/19). On MRI (n = 14/19), non-neurogenic PNM tended to be small (< 5 cm, n = 10/14), isointense to muscle on T1-W (n = 14/14), hyperintense on T2-WI (n = 12/14), with enhancement (n = 12/12), low ADC_min (0.5-0.7 × 10-3 mm²/s), and variable metabolic activity (SUV_max range 2.1-13.1). A target sign was absent (n = 14/14) and fascicular sign was rarely present (n = 3/14). Systematic review revealed 89 cases of non-neurogenic PNM.

CONCLUSION

Non-neurogenic PNMs account for 7% of PNT in our series and occur due to metastases and primary intraneural malignancy. Although non-neurogenic PNMs exhibit a non-specific MRI appearance, they lack typical signs of neurogenic tumors such as the target sign. Quantitative imaging features identified by DWI (low ADC) and F¹⁸-FDG PET/CT (high SUV) may be helpful clues to the diagnosis.

Multimodal treatment of an extremely rare desmoplastic small round cell tumor primary to the brachial plexus - A case report and review of literature

Background:

Desmoplastic small round cell tumor (DSRCT) is a rare and aggressive malignant neoplasm typically located in the abdomen or pelvis. Other possible locations are the chest, pleura, scrotum, and central nervous system. DSRCT originally arising from the brachial plexus (BP) is extremely rare, to the best of our knowledge, only two cases have been previously described in the English scientific literature.

Case Description:

The authors present one new case of DSRCT arising from the left BP, the first in this location with rapid progression and in a female patient. We also highlight the importance of multimodal therapy, which included resection and both adjuvant radiation and chemotherapy. Macroscopic and microscopic characteristics of the lesion are detailed, as well as the patient’s status at 56-month follow-up.

Conclusion:

For primary BP DSRCT, aggressive subtotal resection followed by radiation and chemotherapy can be satisfactory for disease control and for maintaining or improving the neurological status.