Abstract
A 58-year-old woman presented with a solitary myofibroma that arose in the sigmoid colon. Computed tomography revealed a highly enhanced intramural mass (1.3-cm maximum diameter) in the proximal sigmoid colon. Histologically, the tumor exhibited a biphasic growth pattern, which comprised haphazardly arranged, interwoven fascicles of plump, myoid-appearing spindle cells with elongated nuclei and abundant eosinophilic cytoplasm, and more cellular areas of primitive-appearing polygonal cells that were arranged in a hemangiopericytomatous pattern. The tumor cells were positive for smooth muscle actin (SMA), and negative for desmin, h-caldesmon, CD34, cytokeratin, S100 protein, and CD117. The Ki-67 labeling index was not high (up to 7%). Based on these histologic and immunohistochemical features, our patient was diagnosed with a myofibroma of the sigmoid colon. The presence of solitary myofibroma in the intestine of an adult requires attention to avoid misdiagnosis as a more aggressive mesenchymal tumor.Virtual SlidesThe virtual silde(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2096403796957687
Highlights
Myofibroma, a benign neoplasm composed of myofibroblastic cells, can occur as a solitary form or as multiple or generalized form [1]
We describe here a solitary myofibroma that arose in the sigmoid colon of a 58-year-old woman, with a review of the relevant literature
Solitary myofibromas involving the intestinal tract are extremely rare in adult patients
Summary
Myofibroma, a benign neoplasm composed of myofibroblastic cells, can occur as a solitary form or as multiple or generalized form (myofibromatosis) [1]. The Ki-67 (1:100; clone 7B11, Invitrogen, UA) labeling index was not high both in the myoid-appearing spindle cells and primitive-appearing tumor cells (up to 7% in the highest area) (Figure 4C,D). Based on these histologic and immunohistochemical features, the tumor was diagnosed as a myofibroma. The typical zonation characterized by peripheral location of the less cellular area composed of a plump, myoid-appearing, spindle cell was not evident. The myoid-appearing spindle tumor cells were strongly positive for smooth muscle actin (SMA, 1:100; clone 1A4, Dako, Glostrup, Denmark), whereas the primitive-appearing tumor cells stained focally (Figure 4A,B). The tumor cells were negative for pan-cytokeratin (CK, 1:400; Novocastra, Newcastle, UK), S100 protein (1:2,000; Dako), CD117
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