Abstract
IntroductionMammary-type myofibroblastoma of the soft tissue is a very rare, benign, mesenchymal neoplasm with myofibroblastic differentiation. To date, 20 cases of extra-mammary myofibroblastoma have been described in literature. To the best of our knowledge, this is the largest extra-mammary myofibroblastoma described in the literature, and the first case reported in this location.Case presentationA 50-year-old Pakistani man presented with a long history of a painless, huge lump on his right thigh. His clinical examination showed normal-looking skin and there was no inguinal lymphadenopathy. The mass was excised with a clinical impression of soft tissue sarcoma. Gross examination showed a huge, well-circumscribed soft tissue mass measuring 34cm in its largest dimension and weighing approximately 13kg. It was partially covered by fat tissue. Histologically, the lesion was composed of a haphazard arrangement of bland spindle-shaped cell fascicles in a thick collagenous and myxoid background. The neoplastic cells showed diffuse and patchy positivity for CD34 and desmin, respectively. No recurrence was seen following surgical excision over a follow-up period of five months.ConclusionsMammary-type myofibroblastoma of the soft tissue is a benign soft tissue neoplasm, and no malignant behavior and/or recurrence after surgical resection has been described, regarding its size and location. As an extremely rare tumor, the correct diagnosis and prompt management is important, and requires careful clinical and pathological workup to rule out the possibility of a malignant neoplasm.
Highlights
Mammary-type myofibroblastoma of the soft tissue is a very rare, benign, mesenchymal neoplasm with myofibroblastic differentiation
As an extremely rare tumor, the correct diagnosis and prompt management is important, and requires careful clinical and pathological workup to rule out the possibility of a malignant neoplasm
This tumor is most often confused with spindle cell lipoma, as both are spindle cell neoplasms, both are positive for CD34, and in addition at the molecular level, both reveal similar loss of genetic material from the 13q14 region [3,5]
Summary
Mammary-type myofibroblastoma of the soft tissue is a benign, soft tissue neoplasm, and no malignant behavior and/or recurrence after surgical resection has been described in the cases reported so far. As an extremely rare tumor, the correct diagnosis and prompt management is important, and requires careful clinical and pathological workup and extensive sectioning after surgical excision to demonstrate the presence or absence of necrosis, mitosis, or nuclear atypia, and rule out a malignant neoplasm. JAG was major contributor to the writing of the manuscript. NUD and ZA diagnosed the case, and were major contributors for critically revising the manuscript for important intellectual content. All authors read and approved the final manuscript. Author details 1Department of Pathology and Laboratory Medicine, Aga Khan University Hospital, Stadium Road, P.O. Box 3500 Karachi, Pakistan. Box: 472 Kabul, Afghanistan. 3Department of Pathology, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, USA
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