<p>Endometriosis is a prevalent gynecological disorder defined by the growth of tissue resembling endometrial glands and stroma outside the uterus. Extrapelvic endometriosis comprises a minority of cases, with an estimated occurrence in about 12% of individuals diagnosed with the disease. A particularly rare subset of this condition involves the skeletal muscular system (ESMS), in which endometrial tissue implants within muscle fibers. We report a 26 years old woman with a painful forearm mass radiologically suggestive of cavernous hemangioma. Histopathology revealed coexisting intramuscular endometriosis without pelvic disease. Surgical excision resolved symptoms. This case emphasizes considering extrapelvic endometriosis in unexplained soft tissue lesions in reproductive aged women. Diagnosis can be elusive due to the variability in symptoms. Accurate diagnosis often necessitates a multidisciplinary approach. MRI can help identify such lesions, histological analysis remains the definitive method for confirming the presence of endometriotic tissue (1). The exact etiology of endometriosis remains uncertain, though multiple theories aim to explain its varied manifestations. Of particular relevance to muscular involvement are the lymphatic and hematogenous dissemination theories, stem cell theory, iatrogenic implantation, and an impaired immune response. It is plausible that repeated mechanical trauma or intense physical activity may facilitate the formation of such lesions by inducing local inflammation or vascular changes that promote cell migration and implantation. This could explain occurrences in patients without prior surgeries or pelvic disease (3). Early detection and appropriate intervention—whether surgical or medical—are crucial to symptom resolution and preventing recurrence. Recognizing atypical presentations of endometriosis expands our understanding of the disease and improves patient care.</p>