Fibroidid

Fibroidid is a descriptive term used in pathology to denote tissue or lesions that resemble fibroids (leiomyomas) in their gross or microscopic appearance. It is not a formal taxonomic name, and its usage is limited and not standardized across specialties or regions.

Origin and meaning: The term combines "fibroid," referring to fibrous or smooth muscle tumors known as leiomyomas, with the suffix "-id," indicating resemblance. It may be applied to lesions arising in the uterus or in extrauterine sites where smooth muscle proliferation occurs but the lesion does not meet criteria for a true leiomyoma.

Morphology and diagnosis: Fibroidid lesions typically show whorled or interlacing bundles of spindle-shaped cells with fibrous stroma. Atypia is usually absent or minimal; mitotic activity is low unless malignant potential is suspected. Immunohistochemistry, when performed, often demonstrates positivity for smooth muscle markers such as desmin and smooth muscle actin, supporting smooth muscle lineage.

Clinical significance: The designation is descriptive and guides differential diagnosis rather than a standalone diagnosis. Distinguishing fibroidid lesions from actual leiomyomas or malignant smooth muscle tumors (e.g., leiomyosarcoma) relies on histopathologic criteria, tumor location, and growth pattern. Management depends on the underlying entity and clinical context.

Usage and reception: Because it is informal, fibroidid is encountered mainly in case reports or explanatory notes and is not part of formal tumor taxonomy.

See also: fibroid, leiomyoma, leiomyosarcoma, pathology.