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Abstract

Glomus tumor of uncertain malignant potential (GTUMP) is classified when not fulfilling malignant criteria but presents with at least one atypical feature: deep-seated locations, tumor size >2 cm, mitosis > 5/50 high power field (HPF) with mild to moderate nuclear atypia. Due to scant clinical data of these tumors in extremities, this study was undertaken.
Our 24-year retrospective study includes resections from 14 patients which had available follow up (6 females, 8 males), ranging from 32 to 82 years old (median 54). Nine tumors were located on the upper extremities (including three of them at acral sites) and five of them on the lower extremities. Eight tumors were deep seated, involving deep fascia or muscle. Tumor size ranged from 2.1-5.0 cm (median, 3). Cytological atypia varied from mild to moderate. Six cases showed increased mitotic activity ranging from 6-13/50 HPF (median 9) with no atypical mitotic forms and no necrosis. Follow-up ranged from 18 to 273 months (median 97). Two patients had recurrences, with one of them experiencing a local recurrence at 18mths (acral), and the second case had metastatic recurrence (lung) following 2 weeks of initial resection and died of disease at 61 months.

Our study suggests, that although GTUMP tend to have a favorable outcome following complete resection; cases with >2 cm size, moderate atypia and significant mitosis need longer surveillance and tend to have potential risk of recurrence in extremities.