Final answer:
An endometrial biopsy is the most appropriate test to further differentiate the mass within the endometrial canal in a patient with intermenstrual bleeding, as it provides a definitive diagnosis.
Step-by-step explanation:
To further differentiate the mass within the endometrial canal of a 30-year-old patient presenting with intermenstrual bleeding, an endometrial biopsy is the most appropriate test.
This procedure involves taking a sample of tissue from the endometrial lining for microscopic examination to check for abnormal cells or other pathology.
While a transvaginal ultrasound has already revealed a mass, the biopsy provides a definitive diagnosis by allowing a direct visual inspection and analysis of the endometrial tissue. Other tests such as hysterosalpingogram, sonohysterogram with color Doppler, and transrectal sonogram may provide additional imaging details but do not offer the same level of diagnostic specificity as an endometrial biopsy.