In classical/Greek-based medical terminology, many singular nouns ending in -oma (e.g., hematoma, fibroma, carcinoma, sarcoma) can take the plural -omata (hematomata, fibromata, carcinomata, sarcomata). This is the older, more classical plural; in modern clinical English, you will also see and chart -omas as an acceptable plural (e.g., “multiple fibromas”), but -omata is still correct and shows up in pathology texts and some formal writing.
-itis (inflammation) and -oma can intersect in cancer terms historically (e.g., lymphoma vs lymphadenitis).
Coding angle (ICD-10-CM/CPT)
Coding systems don’t distinguish between -oma and -omata / -omas; they just care about:
The type of tumor (benign vs malignant, site, histology).
The number and location when that impacts code choice or modifiers.
Examples you’ll see conceptually (no single code for “-omata”):
Malignant neoplasms (e.g., various C codes in ICD-10-CM for carcinomas, sarcomas).
Benign neoplasms (D codes) or neoplasms of uncertain behavior, all built on -oma roots in the diagnostic term.
For your Obsidian setup, I’d give -oma its main entry and note -omata under it as “classical plural of -oma = multiple tumors/masses,” with a quick reminder that modern charts often use -omas instead.