Spindle-cell squamous carcinoma exhibiting myofibroblastic differentiation

Abstract

The features of two spindle-cell carcinomas of the dermis are described with special reference to the presence of fibronexus junctions in tumour cells. The cases were of a 78-year-old man with a left eye-lid tumour and a 78-year-old woman with a naso-labial fold tumour, who had been given radiotherapy 13 years earlier for a clinically diagnosed basal cell carcinoma. Both specimens were slightly ulcerated and polypoid. Histologically, invasive tumour consisted of interlacing fascicles of plump spindled and oval cells, which were positive for several anti-cytokeratin antibodies, epithelial membrane antigen, vimentin and smooth-muscle and muscle-specific actins. Ultrastructurally, tumour cells in both cases contained rough endoplasmic reticulum (prominent in case 1), tonofibrils, desmosomes and smooth-muscle type myofilaments with focal densities. Fibronexus junctions were also present, which correlated with positive staining for fibronectin. This is the first documentation of the fibronexus in epithelial tissue in vivo, and the first unambiguous demonstration in a spindle-cell carcinoma. It extends the known distribution of the fibronexus and expands the ultrastructural spectrum of squamous carcinoma.

The myofibroblast and its tumours

“…Myofibroblastic differentiation has also been reported in sarcomatoid carcinoma201 where fibronexuses have been observed 202. Cytokeratin positivity can be maintained or partially lost with the change of cell shape, which is associated with expression of α-SMA and muscle-specific actin but not desmin 203…”

Primary and metastatic high-grade pleomorphic sarcoma/malignant fibrous histiocytoma of the gastrointestinal tract: an approach to the differential diagnosis in a series of five cases with emphasis on myofibroblastic differentiation

“…Although the occurrence of lowgrade myofibroblastic sarcoma was recognized by the current WHO classification of soft tissue tumours [28], the concept of 'pleomorphic myofibrosarcoma' is not generally accepted. The nature and significance of the myofibroblast-like phenotype seen in MFH and other pleomorphic neoplasms (specific line of differentiation vs a common final pathway for undifferentiation) is still controversial [13,31]. Likewise, cutoffs for minimal criteria for diagnosing 'pleomorphic myofibrosarcoma' and the potential clinical relevance of such a diagnosis remain to be defined.…”

Low-grade abdominopelvic sarcoma with myofibroblastic features (low-grade myofibroblastic sarcoma): clinicopathological, immunohistochemical, molecular genetic and ultrastructural study of two cases with literature review

“…Sarcomatoid carcinoma (spindle cell carcinoma) may occasionally show myofibroblastic differentiation by immunohistochemistry and electron microscopy 6 7. However, these neoplasms usually show evidence of origin from an epithelial surface and they are reactive for pankeratin markers 7…”

“…This controversy has focused mainly on the problematic definition of a “neoplastic myofibroblast”1 2 and the role and necessity of electron microscopy (as the sole final diagnostic tool of myofibroblastic differentiation in the view of some authors) 3. The issue is further complicated by the phenotypic heterogeneity of myofibroblasts,4 the ubiquity of myofibroblasts in many soft tissue sarcomas,5 and the observation of myofibroblastic differentiation in non-myofibroblastic neoplasia 6 7. Nevertheless, the existence of sarcomas with cytomorphological, architectural, immunohistochemical and ultrastructural features of myofibroblasts is accepted by most soft tissue experts, who currently look at them as an emerging new diagnostic category in the pathology of soft tissue neoplasia 8 – 10.…”