J Pathol Transl Med.  2016 Sep;50(5):385-389. 10.4132/jptm.2016.03.26.

Mammary-Type Myofibroblastoma: A Report of Two Cases

• An S
• Song JS
• Park S
• Lee JW
• Cho KJ

• KMID: 2353601
• DOI: http://doi.org/10.4132/jptm.2016.03.26

Abstract

Mammary-type myofibroblastoma (MFB) is a rare, benign spindle cell neoplasm occurring along the milkline, with extension from the mid-axilla to the medial groin. It is histologically and immunohistochemically identical to MFB of the breast and is part of a spectrum of lesions that includes spindle cell lipoma and cellular angiofibroma. Recently, we experienced two cases of mammary-type MFB involving male patients aged 30 and 58 years, respectively. The tumors were located in the right scrotal sac and in the right axilla. Wide excisions were performed. Microscopically, the masses were composed of haphazardly arranged, variably sized fascicles of bland spindle cells and were admixed with mature fat tissue. The spindle cells in both cases showed immunopositivity for desmin and CD34 and negativity for smooth muscle actin. Loss of retinoblastoma (RB)/13q14 loci is a characteristic genetic alteration of mammary-type MFB, and we identified loss of RB protein expression by immunohistochemical staining. We emphasize the importance of awareness of this rare neoplasm when a spindle cell neoplasm is accompanied by desmin immunopositivity. The second patient was alive without recurrence for 20 months, and the first patient had not been followed.

Keyword

Mammary-type myofibroblastoma; Milkline; 13q14

MeSH Terms

Actins
Angiofibroma
Axilla
Breast
Desmin
Groin
Humans
Lipoma
Male
Muscle, Smooth
Neoplasms, Muscle Tissue*
Recurrence
Retinoblastoma
Retinoblastoma Protein
Actins
Desmin
Retinoblastoma Protein

Figure

• 

  Fig. 1. Radiologic findings for the two study cases. (A) In case 1, a pelvis computed tomography (CT) shows 5.0 cm mass in the right scrotal sac separated from the adjacent testis and spermatic cord (arrow). (B) In case 2, a chest CT shows a 5.5 cm lobulated mass in the right axilla (arrowhead).

• 

  Fig. 2. Gross and microscopic findings of case 1. (A) The cut surface is yellowish tan, rubbery, and trabeculated, without necrosis or hemorrhage. (B) The mass is composed of haphazardly arranged and variably sized fascicles of bland spindle cells. Tumor cells have tapered nuclei and fine chromatin. Numerous mast cells are scattered (arrows). No mitosis is observed. The tumor cells show immunopositivity for desmin (C) and CD34 (D).

• 

  Fig. 3. Gross and microscopic findings of case 2. (A) The cut surface is yellowish tan, smooth, and glistening, and a focal myxoid change is observed. (B) The mass is well demarcated with mature adipocytes. (C) Staghorn-like blood vessels are present, with focal hyalinization. Tumor cells shows immunopositivity for desmin (D) and estrogen receptor (E). (F) Retinoblastoma immunostaining shows negativity.

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