Mammary-type myofibroblastoma of the right thigh: a case report and review of the literature

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.

Mammary-type myofibroblastoma of the psoas

“…Therefore, it has been theorised that extra-MTMFs occur along the embryonic milk-line from the axilla to the medial groin; however, these tumours have frequently been found in other locations as well. Extra-MTMFs have been described to occur in the paratesticular region,6 scrotal sac,21 seminal vesicle,13 prostate,4 vulva,9 12 perianal region,10 buttock region,11 periumbilical region,20 internal oblique muscle,19 liver,2 mandibular angle,8 eye,15 popliteal fossa,7 axilla,21 thigh17 and big toe 16. Furthermore, MTMF arising in the retroperitoneum as in this patient was described in one case series 18.…”

“…The differential diagnosis for extra-MTMF includes neoplasms of a benign (benign nerve sheath tumour, solitary fibrous tumour, leiomyoma, spindle cell lipoma (SCL), cellular angiofibroma, angiofibroblastoma, angiomyxoma and soft tissue perineurioma) and malignant (liposarcoma, dermatosarcoma protuberans) nature 14 17. However, extra-MTMF is most often confused with SCL since they are both composed of CD34 positive spindle cells interspersed with adipose tissue 5 17.…”

“…However, extra-MTMF is most often confused with SCL since they are both composed of CD34 positive spindle cells interspersed with adipose tissue 5 17. Additionally, both of them may demonstrate a loss of the RB1 and FOXO1 gene on chromosome 13q14 5 17 21 24 25. The differentiating factor lies in SCL's lack of desmin staining in contrast to extra-MTMF which generally stains for desmin 5 17.…”

“…Additionally, both of them may demonstrate a loss of the RB1 and FOXO1 gene on chromosome 13q14 5 17 21 24 25. The differentiating factor lies in SCL's lack of desmin staining in contrast to extra-MTMF which generally stains for desmin 5 17. Furthermore, the adipose tissue component of extra-MTMF is less than that in SCL 17…”

Mammary myofibroblastoma in the right lateral abdominal wall

“…Extramammary myofibroblastomas have been reported more frequently. Previous reports [ 2 , 3 ] have suggested that the inguinal/groin region is the usual site for extramammary myofibroblastomas. The tumor usually consists of spindle cells [ 4 ] and lacks genetic material in the 13q14 region [ 5 ].…”